U.S. patent application number 13/204529 was filed with the patent office on 2011-12-01 for monolithic column chromatography.
This patent application is currently assigned to Quest Diagnostics Investments Incorporated. Invention is credited to Nigel Clarke, Mildred M. Goldman.
Application Number | 20110290999 13/204529 |
Document ID | / |
Family ID | 39316930 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110290999 |
Kind Code |
A1 |
Clarke; Nigel ; et
al. |
December 1, 2011 |
MONOLITHIC COLUMN CHROMATOGRAPHY
Abstract
Provided herein are methods of liquid column chromatography in
which preparative chromatography is performed in-line with
analytical chromatography. In particular aspects a monolithic
preparative column is used to purify an analyte of interest from a
mixture of other substances by applying the mixture to the column,
reversing the flow through the column to elute the analyte, which
is applied to an analytical column provided in-line with the
preparative column. In other aspects, a single monolithic column is
used to perform both the preparative chromatography and analytical
chromatography steps in succession. In another aspect, a
chromatography system is provided to perform preparative and
analytical chromatography using a single monolithic column.
Inventors: |
Clarke; Nigel; (Oceanside,
CA) ; Goldman; Mildred M.; (Laguna Niguel,
CA) |
Assignee: |
Quest Diagnostics Investments
Incorporated
|
Family ID: |
39316930 |
Appl. No.: |
13/204529 |
Filed: |
August 5, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11584354 |
Oct 20, 2006 |
8017015 |
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13204529 |
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Current U.S.
Class: |
250/282 ;
210/656; 210/659; 73/61.52; 977/780 |
Current CPC
Class: |
B01J 2220/82 20130101;
B01J 20/28083 20130101; G01N 30/52 20130101; B01D 15/1871 20130101;
G01N 30/60 20130101; B01D 15/1864 20130101; B01D 15/34 20130101;
G01N 2030/407 20130101; B01J 20/28085 20130101; G01N 30/72
20130101; G01N 2030/528 20130101; B01D 15/1814 20130101; G01N
2030/8813 20130101; G01N 30/461 20130101; G01N 30/88 20130101; G01N
30/48 20130101; G01N 30/40 20130101 |
Class at
Publication: |
250/282 ;
210/656; 210/659; 73/61.52; 977/780 |
International
Class: |
B01D 15/42 20060101
B01D015/42; H01J 49/26 20060101 H01J049/26; B01D 15/08 20060101
B01D015/08; G01N 30/00 20060101 G01N030/00 |
Claims
1. A chromatographic method for detecting one or more analytes in a
body fluid sample containing one or more other substances, said
method comprising: a) applying a body fluid sample to a monolithic
chromatography column comprising a monolithic sorbent having
macropores and mesopores; b) applying a first mobile phase to said
monolithic chromatography column after applying said body fluid
sample under conditions such that one or more analytes are retained
on said monolithic chromatography column and one or more other
substances present in said body fluid sample are removed, wherein
said one or more retained analytes have a molecular weight of less
than about 5,000 Daltons; c) eluting said one or more retained
analytes by applying a second mobile phase to said monolithic
chromatography column; and d) detecting said one or more analytes
eluted in step c).
2. The method of claim 1, wherein said second mobile phase is
applied to said monolithic chromatography column in the opposite
direction of the flow of step (b).
3. The method of claim 1, wherein said body fluid sample comprises
an isolated body fluid selected from the group consisting of blood,
plasma, serum, bile, saliva, urine, tears, synovial fluid,
peritoneal fluid, bronchial-alveolar lavage, CSF, and
perspiration.
4. The method of claim 1, wherein said macropores have a median
diameter of 0.1 to 50 .mu.m.
5. The method of claim 4, wherein said macropores have a median
diameter of 2 to 20 .mu.m.
6. The method of claim 1, wherein said mesopores have a median
diameter of 2 to 100 nm.
7. The method of claim 1, wherein said mesopores comprise a fatty
acid linked to said mesopore.
8. The method of claim 7, wherein said fatty acid is selected from
the group consisting of butyric acid (C4), caprylic acid (C8), and
stearic acid (C18).
9. The method of claim 1, wherein said one or more analytes
retained on said first column have a molecular weight of less than
about 1,000 Daltons.
10. The method of claim 1, wherein said one or more analytes
retained on said first column have a molecular weight of less than
about 500 Daltons.
11. The method of claim 1, wherein said other substances are
proteins or proteinaceous material.
12. The method of claim 1, wherein the eluted one or more eluted
analytes are directed to a mass spectrometer for detection in step
d).
13. The method of claim 1, wherein said body fluid sample applied
to the chromatography column in step a) comprises an isolated body
fluid mixed with one or more liquids.
14. The method of claim 1, further comprising: directing said one
or more analytes eluted in step c) to a packed capillary spray tip
in-line with said first column for further separation prior to step
d).
15. The method of claim 1, further comprising: reapplying said one
or more analytes eluted in step c) to said monolithic
chromatography column under conditions whereby a second
chromatographic separation is achieved prior to detection in step
d).
16. The method of claim 15, further comprising: reapplying the
eluted one or more analytes from said second chromatographic
separation to said monolithic column under conditions whereby a
third chromatographic separation is achieved prior to detection in
step d).
17. A method for achieving a chromatographic separation of one or
more analytes from one or more other substances in a body fluid
sample, said method comprising: a) applying a body fluid sample to
a monolithic chromatography column comprising a monolithic sorbent
having macropores and mesopores; b) applying a first mobile phase
to said monolithic chromatography column after applying said body
fluid sample under conditions such that said one or more analytes
in the sample are retained on said monolithic chromatography column
and one or more other substances are removed, wherein said one or
more retained analytes have a molecular weight of less than 5,000
daltons; and c) eluting said one or more retained analytes by
applying a second mobile phase to said monolithic chromatography
column.
18. The method of claim 17, wherein said second mobile phase is
applied to said monolithic chromatography column in the opposite
direction of the flow of step (b).
19. The method of claim 17, wherein said body fluid sample
comprises an isolated body fluid selected from the group consisting
of blood, plasma, serum, bile, saliva, urine, tears, synovial
fluid, peritoneal fluid, bronchial-alveolar lavage, CSF, and
perspiration.
20. The method of claim 17, wherein said macropores have a median
diameter of 0.1 to 50 .mu.m.
21. The method of claim 17, wherein said macropores have a median
diameter of 2 to 20 .mu.m.
22. The method of claim 17, wherein said mesopores have a median
diameter of 2 to 100 nm.
23. The method of claim 17, wherein said mesopores comprise a fatty
acid linked to said mesopore.
24. The method of claim 23, wherein said fatty acid is selected
from the group consisting of butyric acid (C4), caprylic acid (C8),
and stearic acid (C18).
25. The method of claim 17, wherein said one or more analytes
retained on said first column have a molecular weight of less than
1,000 daltons.
26. The method of claim 17, wherein said one or more analytes
retained on said first column have a molecular weight of less than
500 daltons.
27. The method of claim 17, wherein said other substances are
proteins or proteinaceous material.
28. The method of claim 17, wherein said body fluid sample applied
to the monolithic chromatography column in step a) comprises an
isolated body fluid sample mixed with one or more liquids.
29. The method of claim 17, wherein said one or more of said eluted
analytes are directed to a second chromatography column for further
chromatographic separation.
30. The method of claim 17, wherein one or more of said eluted
analytes are directed to a devise suitable for detecting said one
or more eluted analytes.
31. The method of claim 30, wherein said devise comprises a mass
spectrometer.
32. The method of claim 17, further comprising: reapplying said one
or more analytes eluted in step c) to said monolithic
chromatography column under conditions whereby a second
chromatographic separation is achieved.
33. The method of claim 32, wherein one or more of said eluted
analytes are directed to a devise suitable for detecting said one
or more eluted analytes following said second chromatographic
separation.
34. The method of claim 33, wherein said devise comprises a mass
spectrometer.
35. The method of claim 32, further comprising: reapplying the
eluted one or more analytes from said second chromatographic
separation to said monolithic column under conditions whereby a
third chromatographic separation is achieved.
36. The method of claim 35, wherein one or more of said eluted
analytes are directed to a devise suitable for detecting said one
or more eluted analytes following said second chromatographic
separation.
37. The method of claim 36, wherein said devise comprises a mass
spectrometer.
Description
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn.120
to U.S. application Ser. No. 11/584,354, filed Oct. 20, 2006,
incorporated herein by reference in its entirety.
[0002] 1. Field of the Invention
[0003] The present invention relates generally to the field of
liquid column chromatography.
[0004] 2. Background of the Invention
[0005] Analytical liquid chromatography (e.g., high performance
liquid chromatography or HPLC) is commonly used in the detection
and quantitation of low molecular weight substances in biological
samples and body fluid samples (e.g., blood, serum, or plasma).
Such samples contain proteins and proteinaceous molecules, which
can accumulate on many types of HPLC columns, thereby causing
irreversible damage to such columns. For this reason, it is
desirable to remove the proteins and other large molecular weight
species prior to analysis of the sample for the analyte of
interest. Methods of removal of proteins include precipitation,
membrane filtration, and liquid-liquid or liquid-solid phase
extraction.
[0006] An alternate method of removing proteins from a sample is
preparative liquid chromatography. In order to adapt such a method
to high throughput assays, high flow rates, short elution times,
and moderate operating pressures are desirable. Accordingly, porous
support materials for use in column chromatography which,
simultaneously offer a selective retention of low molecular weight
analytes (molecular weight<5000 Dalton), and make possible
quantitative separation of proteins and other macromolecular
components in a directly injected sample have recently been
developed. One example of a column comprising such a porous support
is a new column for use in HPLC, known as a monolithic column.
Monolithic columns, in contrast to traditional HPLC columns that
comprise packed particles, contain a single, solid compound as the
stationary phase. This stationary phase is usually made up of a
network of polymethacrylate or polystyrene copolymers, or bonded
silica forming pores of varying size. Thus, in monolithic columns
the mobile phase must flow through the pores of the solid
stationary phase. Molecules within the mobile phase are then
retained to a greater or lesser extent within the pores of the
stationary phase (small molecules diffuse into the pores and are
retained while large molecules are excluded from the pores and are
not retained). Retention of small molecules may be further enhanced
by binding to specific compounds incorporated into the interior of
the pores.
SUMMARY OF THE INVENTION
[0007] Provided herein are methods of performing preparative liquid
chromatography, using a monolithic column, in-line with analytical
liquid chromatography. In such methods, an analyte or analytes of
interest are separated from other substances in a complex mixture
using a monolithic column under conditions whereby the analyte is
retained on the column. The analyte is then eluted and supplied to
an in-line analytical column for further separation and detection.
Such methods offer the advantage of utilizing a monolithic column
in the preparative chromatography, which allows for higher flow
rates at moderate operating pressures, resulting in quick
separations. The further combining of preparative chromatography
in-line with analytical chromatography decreases the amount of
handling by the operator which results in a fast, efficient, and
inexpensive method amenable to high-throughput assays.
[0008] In one aspect of the invention, there are provided
chromatographic methods for detecting one or more analytes in a
sample containing a mixture of other substances. Such methods
comprise: a) separating the one or more analytes from the other
substances in a mixture using a first chromatography column
comprising a monolithic sorbent having macropores and mesopores,
using a first mobile phase under conditions such that the one or
more analytes are retained on the first column and other substances
are removed, b) eluting the one or more retained analytes by
applying a second mobile phase to the column, c) directing the
eluted one or more analytes to a second chromatography column
in-line with the first column for further separation, and d)
detecting the one or more analytes following the separation in step
c).
[0009] In some embodiments the second mobile phase is applied to
the column in the same direction as the flow in step a). In other
embodiments, the second mobile phase is applied to the column in
the opposite direction of the flow in step a).
[0010] In some embodiments, a monolithic column is used to separate
small molecular weight analytes of interest from a mixture of large
molecular weight species. Thus, a sample is loaded onto a
monolithic column, comprising macropores and mesopores under
conditions such that small molecule analytes are retained, while
larger molecules are excluded and washed from the column with the
eluent. After the large molecular weight species have been removed,
the small molecule analyte is eluted from the column with a reverse
flow of mobile phase and supplied directly to an in-line analytical
column for further separation and analysis.
[0011] The above method can be applied to obtain preparative
samples of small molecular weight analyte from various types of
body fluids and using monolithic columns with various physical
characteristics.
[0012] In another aspect of the invention, there are provided
methods for achieving multiple chromatographic separations of one
or more analytes from other substances in a sample using a single
column. Such methods comprise: a) achieving a first chromatographic
separation of one or more analytes from other substances, the
separation occurring by applying the sample to a chromatography
column comprising a monolithic sorbent having macropores and
mesopores, using a first mobile phase under conditions such that
the one or more analytes in the sample are retained on the column
and other substances are removed, b) eluting the one or more
retained analytes by applying a second mobile phase to the column
in the opposite direction of the flow in step a), c) applying the
eluted one or more analytes to the column under conditions whereby
a second chromatographic separation is achieved. Such methods allow
for the use of fewer columns and fewer HPLC pumps, resulting in a
reduction in cost as well as savings in space. In addition, use of
the column for analytical separation allows for enhanced recovery
of analyte that may have remained adsorbed to the column during the
first chromatographic separation.
[0013] In some embodiments of the above aspect of the invention,
the first chromatographic separation is a preparative
chromatographic separation and the second chromatographic
separation is an analytical separation. In this method, a mixture
containing small molecule analytes and larger molecules is applied
to the monolithic column under conditions such that the small
molecule analytes are retained on the column, whereas the large
molecules pass through the column. One or more analytes of interest
are then eluted using a reverse flow of a small volume of an
organic solvent and recovered into a precolumn reservoir. The
eluted one or more analytes are then resupplied to the monolithic
column, and the system run under conditions sufficient for
chromatographic separation and detection of the analyte or analytes
of interest.
[0014] In certain embodiments of the above aspect of the invention,
step c) further comprises retaining the one or more analytes on the
column and eluting the one or more analytes using reverse flow. The
eluted analytes may then be reapplied to the column under
conditions whereby a third chromatographic separation is
achieved.
[0015] In other embodiments of the above aspect of the invention,
step c) further comprises running the one or more analytes through
the column and monitoring the effluent for the one or more
analytes. Monitoring may be performed by any of a number of
instruments or detectors well-known to those of skill in the art.
For example, analytes may be detected using mass
spectrometrometers, UV/Vis absorbance detectors, photodiodearray
detectors, fluorescence detectors, refractive index detectors,
conductivity detectors, and the like.
[0016] In still other embodiments of the above aspect of the
invention, step c) further comprises collecting the one or more
analytes into fractions following the second (or third, etc.)
chromatographic separation. Such fractions may be subjected to
further analysis by chromatographic methods or other standard
analytical methods.
[0017] The above methods can be applied to obtain preparative
samples of small molecular weight analyte from various types of
body fluids and using monolithic columns with various physical
characteristics.
[0018] In another aspect of the invention, there is provided a
chromatography system for achieving multiple chromatographic
separations of one or more analytes from other substances in a
sample using a single monolithic column. Such a system comprises as
a central feature a multiport valve and a column comprising a
continuous monolithic sorbent having interconnected macropores and
mesopores. The system further includes a mobile phase supply, a
sample injector, a reservoir, a detector, and a waste line. The
system is configured as follows: the mobile phase supply connected
to the sample injector, which is connected to one port of the
multiport valve having individual ports. Each port of the multiport
valve is further connected to one of the following: a reservoir
(having a first end and a second end and wherein the reservoir is
adapted to hold eluted analyte) wherein the first end of the
reservoir is in fluid communication with a port of the valve and
the second end of the reservoir is in fluid communication with a
first opening of a column; a second opening of the column; a
detector; and a waste line. The multiport valve is switchable
between a first position and a second position. In the first
position of the valve, the mobile phase supply (via the sample
injector) is connected to the valve which is connected to the
sample loop which is connected to the first opening of the column.
The second opening of the column is connected to the valve which is
further connected to the detector. In the second position of the
valve, the orientation of the column with respect to the system is
o reversed so that the mobile phase supply is connected, via the
valve to the second opening of the column. The first opening of the
column is connected to the sample loop which is connected to the
valve which is connected to the waste line.
[0019] The two operating positions of the multiport valve determine
the direction of flow of mobile phase through the column. In the
first position, fluid from the mobile phase supply travels via the
sample injector to the valve which directs the flow through the
reservoir, and into the first end of the column. Flow exits the
column via the second opening of the column and enters the valve
and is directed to a detector. When the valve is in the second
position, the mobile phase enters the column through the second
opening of the column and exits via the second opening, thus
providing a flow of mobile phase through the column in the opposite
direction as the flow of mobile phase when the valve is in the
first position. Exiting mobile phase is further directed to a waste
line.
[0020] In a particular embodiment of the above aspect of the
invention, the system further comprises a second multiport valve.
In this system the two valves are connected in tandem. Each port of
the first multiport valve is connected to one of the following: a
sample injector; a reservoir, having a first end and a second end
and wherein the reservoir is adapted to hold eluted analyte,
wherein the first end is in fluid communication with a port of the
first multiport valve and the second end is in fluid communication
with a first opening of a column, a second opening of the column;
and a second multiport valve. The second multiport valve is further
connected to one or more detectors and a waste line. The first
multiport valve is switchable between a first position and a second
position so that the valve controls the direction of the flow of
mobile phase through the column. The second multiport valve is
switchable between a first position and a second position so that
the valve controls the flow of effluent to the detector or the
waste line. Thus, the user of the system can change the orientation
of the column with respect to the system (i.e., reverse the flow of
solvent through the column) using the first valve. Further, the
user can determine whether a particular detector or a waste line is
in-line using the second valve.
[0021] In such a system, a sample is applied to the column using
the solvent delivery system and the sample injector under
conditions whereby small molecules are retained on the column while
large molecular weight species flow through the column and are not
retained. The solvent and large molecular weight species may be
conducted to a waste line or to an in-line detector to monitor
removal of the large molecules. Once the large molecular weight
species have been washed from the column, flow of solvent through
the column is reversed and the analyte is eluted from the column
into the reservoir. Flow is reversed again and the analyte is
reapplied to the column for further analytical separation.
Following the analytical separation, the eluted analyte may be
conducted to any of the one or more in-line detectors.
[0022] "Monolithic column" as used herein comprises a material
(e.g., silica, glass, glass-ceramic, or polymeric components)
having interconnected continuous macropores with a median diameter
larger than 0.1 .mu.m. A monolithic column also may additionally
contain mesopores in the walls of the macropores. Mesopores
preferably have a median diameter between 2 and 100 nm.
[0023] The interconnected macropores in the porous materials of a
monolithic column may exhibit median diameters ranging from 0.1 to
50 .mu.m; a preferred range for the median diameters of the
macropores is from 0.2 to 20 .mu.m or 0.2 to 10 .mu.m.
[0024] Mesopores present in the walls of the macropores exhibit
median diameters ranging from 2 to 100 nm; a preferred range for
the median diameters of the mesopores is from 2 to 50 nm, and
especially a range from 5 to 30 nm being preferred.
[0025] "Phenyl," "C-2," "C-8," and "C-18" as used herein refer to
functional groups present on a column packing material. For
example, a phenyl column exposes the material flowing through the
column to unsubstituted phenyl groups, while a C-18 column exposes
the material flowing through the column to unsubstituted straight
or branched chain 18-carbon alkyl groups.
[0026] In some embodiments, the inner surface of the macro or
mesopore is chemically modified. In particular aspects, the
interior of the mesopores of a monolithic column are coated with a
C4, C8, C18, or phenyl material to assist in the retention of
hydrophobic analytes.
[0027] "Liquid chromatography" (LC) as used herein means a process
of selective retention or retardation of one or more components of
a fluid solution as the fluid flows through a column containing
stationary material(s) made of a finely divided substance and/or a
material having capillary passageways. Retention results from the
relative partitioning of the components of the mixture between the
stationery phase and the bulk fluid phase (i.e., mobile phase), the
later of which moves through the stationery materials. LC is used
for analysis and separation of mixtures of two or more substances.
LC includes, for example, high turbulence liquid chromatography
(HTLC), preparative chromatography, and analytical chromatography
(e.g., HPLC).
[0028] "High turbulence liquid chromatography" (HTLC) as used
herein refers to the use of turbulent flow to enhance the rate of
mass transfer during column chromatography, improving the
separation characteristics provided. This is in contrast to
traditional HPLC analysis which relies on column packings in which
laminar flow of the sample through the column is the basis for
separation of the analyte of interest from the test sample. HTLC
has been applied for sample preparation to detect drugs prior to
analysis by mass spectrometry. See, e.g., Zimmer et al., J.
Chromatogr. A 854: 23-35 (1999); see also, U.S. Pat. Nos.
5,968,367; 5,919,368; 5,795,469; and 5,772,874.
[0029] "Preparative chromatography" as used herein refers to coarse
separation of a particular analyte from a mixture containing other
substances that are grossly different from the analyte (e.g., a
small molecule analyte may be separated from a mixture containing
proteins and other large molecular weight species). Such methods
involve the selective retention of a particular solute or analyte
in a complex mixture by a column, while other components are not
retained. The analyte is then selectively removed from the column
and may be collected for further use or analysis. Typically,
preparative chromatographic separations are followed by a finer
separation, which allows for the separation of closely related
molecules (i.e., analytical chromatography). Preparative
chromatography does not necessarily involve large samples, or large
columns (although very large columns are often used in preparative
chromatography). In preparative chromatography, column diameters
can range from a few millimeters to a meter or more, and mobile
phase volumes may range from a few milliliters to hundreds of
liters. In preparative chromatography, analytes eluted from the
column may be collected in an in-line reservoir (e.g., sample loop
or tubing). Alternatively, analytes, following elution from the
preparative column, may be directed to an in-line analytical column
for further analysis.
[0030] "Analytical chromatography" as used herein refers to a fine
separation of closely related molecules (e.g., molecules of similar
molecular weights). In analytical chromatography, analytes
separated on a column, eluted from the column, and monitored or
detected. The term "analytical column" as used herein refers to a
chromatography column having sufficient chromatographic plates to
effect a separation of an analyte from other materials in a sample,
wherein such a separation is sufficient to allow detection and
determination of the presence or amount of the analyte.
[0031] In methods provided herein a single monolithic column is
used for both preparative chromatography and analytical
chromatography. This is accomplished by changing the conditions
under which each separation is performed. Such conditions include
flow rate, composition of the mobile phase, and the direction of
flow of mobile phase through the column.
[0032] "Separating" as used herein, refers to the process
characterized by the spatial separation of the components of a
mixture based on their partitioning differential between phases
(i.e., mobile and stationary phases) in relative motion. Separating
results from loading the sample onto the column and washing the
column following loading.
[0033] "Loading" as used herein, refers to the application of a
sample to the column until the entire sample is contained within
the column.
[0034] "Washing" as used herein, refers to the process of flowing
solvent through the column after loading so as to remove substances
not adsorbed on the column or substances from which the analyte is
to be separated. Multiple washes are possible using different wash
solutions.
[0035] "Sample" as used herein, refers to any solution comprising a
mixture of large and small molecular weight species. Such samples
include any type of biological samples such as body fluids or
samples derived from cell culture, microorganisms, plants, or
animals.
[0036] "Body fluid" as used herein means any fluid that can be
isolated from the body of an individual. For example, "body fluid"
may include blood, plasma, serum, bile, saliva, urine, tears,
perspiration, synovial fluid, peritoneal fluid, bronchial-alveolar
lavage, CSF, and the like.
[0037] "Small molecular weight species" or a "small molecule
analyte" as used herein refers to a molecule that typically has a
molecular weight of less than 5,000 daltons, more typically less
than 1,000 daltons, and most typically less than 500 daltons.
Following preparative isolation from the monolithic column, the
analytes are then subjected to analytical chromatographic
separation and detection.
[0038] "Large molecular weight species" as used herein refers to a
molecule having a molecular weight in the range of one thousand to
many millions of daltons. Examples include proteins, proteinaceous
substances, nucleic acids, polysaccharides, and other polymers.
"Proteinaceous substances" as used herein refer to any material
that includes a polypeptide as part of the molecule. Proeteinaceous
materials include glycoproteins, proteoglycans, lipoproteins, and
the like. The term protein includes the terms "polypeptide," and
"peptide," which refer to a polymer of amino acid residues. The
term applies to amino acid polymers in which one or more amino acid
residue is a synthetic chemical analogue (e.g.,
para-methyl-tyrosine, para-chloro-phenylanine, and the like) of a
corresponding naturally occurring amino acid, as well as to
naturally occurring amino acid polymers. Amino acids can be in the
L or D form so long as the binding function of the peptide is
maintained. Peptides can be of variable length, generally between
about 4 and 200 amino acids. Peptides may be cyclic, having an
intramolecular bond between two non-adjacent amino acids within the
peptide, e.g., backbone to backbone, side-chain to backbone and
side-chain to side-chain cyclization.
[0039] "In-line" as used herein refers to steps performed in
sequence and in an automated fashion and without the need for
operator intervention. For example, by careful selection of valves
and connector plumbing, two or more chromatography columns can be
connected as needed such that material is passed from one column to
the next without the need for any manual handling steps.
Alternatively, one column may be used in conjunction with one or
more valves and connector plumbing so that the direction of the
flow of mobile phase through the column may be reversed, allowing
for an eluted analyte to be reapplied to the column. Such systems
may require electronic programming of controlling software. In
preferred embodiments, the selection of valves and plumbing is
controlled by a computer pre-programmed to perform the necessary
steps. In some embodiments, the chromatography system is connected
in-line to a detector system, e.g., a mass spectrometry system.
[0040] "Off-line," in contrast, as used herein refers to a
procedure requiring manual intervention of an operator. Thus, if
samples are subjected to precipitation, and the supernatants are
then manually loaded into an autosampler, the precipitation and
loading steps are off-line from the subsequent steps.
[0041] "Eluent" as used herein refers generally to the liquid or
gas entering a chromatographic bed (e.g., a column) used to effect
a separation by "elution."
[0042] "Effluent" refers generally to a liquid that flows out of
something. As used herein, "effluent" refers to the solvent flowing
out of a column. Effluent may contain substances not retained on
the columna or analytes eluted from the column.
[0043] "Reservoir" refers generally to a vessel or container entity
for holding a liquid. As used herein "reservoir" may be used to
hold the analyte after elution from the column. The analyte may be
held in the reservoir until it is, for example, reloaded onto the
column from which it was eluted, or directed to another column.
Examples of reservoirs as used herein include a sample loop or
tubing.
[0044] "Mobile phase source" as used herein refers to a vessel that
holds mobile phase prior to its being utilized in a chromatographic
separation.
[0045] "Hydrophobic" as used herein means not dissolving in water.
"Hydrophobic" compounds include long straight or branched chain
alkanes. A hydrophobic solvent is a solvent that is capable of
dissolving a hydrophobic compound.
[0046] The choice of solvents or mobile phase used depend on the
nature of the column used in a particular preparative or analytical
separation. For example, solvents typically used with reversed
phase columns typically include any miscible combination of water
and various organic liquids (the most common are methanol or
acetonitrile).
[0047] In certain embodiments, an analyte may be purified by
applying a sample to a column under conditions where the analyte of
interest is reversibly retained by the column, while one or more
other materials are not retained. In these embodiments, a first
mobile phase condition can be employed where the analyte of
interest is retained by the column, and a second mobile phase
condition can subsequently be employed to remove retained material
from the column, once the non-retained materials are washed
through. The second mobile phase may be phased in gradually to
generate a concentration gradient, usually under computer control
directing the composition of mobile phase over time, or by an
immediate change in the mobile phase. In some embodiments, removal
is accomplished with the use of a small volume of an organic
solvent. The retained materials may also be removed from the column
by "backflushing" the column, or reversing the direction of flow of
the mobile phase. Such backflushing may be performed with the same
mobile phase used in applying the analyte to the column or may be a
different mobile phase for removing the retained material. This may
be particularly convenient for material that is retained at the top
of the column. Alternatively, an analyte may be purified by
applying a sample to a column under mobile phase conditions where
the analyte of interest elutes at a differential rate in comparison
to one or more other materials.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIGS. 1A-B. Schematic of a two-column chromatography system
comprising a monolithic preparative column and an analytical
column. FIG. 1A shows the system in the first position. FIG. 1B
shows the system in the second position.
[0049] FIGS. 2A-B. Schematic of a single column chromatography
system comprising a single monolithic column and one multiport
valve, assembled so that the monolithic column may be used for both
preparative and analytical chromatography. FIG. 2A shows the valve
in the first position and the direction of the solvent flow during
column equilibration, sample loading, and detection of the eluted
analyte. FIG. 2B shows the valve in the second position during the
isolation of the retained analyte following the preparative
chromatography.
[0050] FIGS. 3A-C. Schematic of a single column chromatography
system comprising a single monolithic column and two multiport
valves (4) and (7) assembled so that the monolithic column may be
used for both preparative and analytical chromatography. FIG. 3A
shows the first and second multiport valves both in the first
position during column equilibration and sample loading. FIG. 3B
shows the position of the first and second multiport valves (second
position and first position, respectively) during the elution of
analytes. FIG. 3C shows the position of the first and second
multiport valves (first position and second position, respectively)
during the elution and detection of the analyte.
[0051] FIG. 4A-C. Schematic of the HTLC system used in the analysis
of estradiol in a sample of serum using a single monolithic column
for extraction and analysis, as described in Example 2.
[0052] FIG. 5. Chromatograms showing the separation of estradiol
and D8-estradiol internal standard in a serum sample from the large
molecule background, produced with the use of a monolithic column
for preparative chromatography in-line with analytical HPLC.
[0053] FIG. 6. Chromatograms showing the separation of estradiol
and D8-estradiol internal standard in a serum sample from the large
molecule background, produced with the use of a monolithic column
for both preparative chromatography and analytical
chromatography.
[0054] FIG. 7A-C Schematic of the HTLC system used in the analysis
of estradiol in a sample of serum using a monolithic column for
preparative chromatography followed by in-line analytical
chromatography using a second column, as described in Example
1.
DETAILED DESCRIPTION OF THE INVENTION
[0055] In particular aspects, a preparative monolithic column is
supplied in-line with an analytical column in a chromatography
system. Such a system is set forth in FIG. 1A-B. Thus, referring to
FIG. 1A, a first mobile phase source (1) is connected to a solvent
delivery system (2) which is connected to a sample injector (3)
which is connected to one port of a multiport valve (4). Other
ports of the multiport valve (4) are connected to the top end of
the preparative monolithic column (5), the bottom end of the
preparative monolithic column (5), waste (6), the top end of the
analytical column (9), and a second solvent delivery system (8),
which is further connected to a second mobile phase source (7). The
bottom end of the analytical column is further connected to a
detector (10), which is connected to an optional data integrator
(11).
[0056] In the operation of the above system, mobile phase (1) is
supplied to the system with a solvent delivery system (2). Samples
are injected into the system downstream of the solvent delivery
system with a sample injector (3) with the multiport valve (4) in
the first position (FIG. 1A). The sample is transferred with mobile
phase or buffer (1) using the solvent delivery system (2) onto the
preparative column (5) containing a monolithic sorbent. The
analytes of interest are selectively retained on the column (5)
based on the size of the analyte, while the remaining biological
materials (proteins etc.) are passed to the waste (6). After the
multiport valve (4) has been switched to the second position (FIG.
1B), the analyte is eluted with the aid of an organic solvent (7)
supplied by a second solvent delivery system (8), running in the
reverse direction through preparative column (5) and supplied to
the downstream analytical column (9). The analytical separation
takes place under conditions sufficient to separate the analytes of
interest. The eluted analytes are measured in the detector (10),
and the data are evaluated in the integrator (11). The multiport
valve is then switched to the first position so that the
preparative column can be conditioned by means of the solvent
delivery system (2) for a new preparative cycle.
[0057] In other aspects, a single monolithic column is used in both
preparative and analytical separations. There are at least two
configurations of such a system. One example of such a system is
set forth in FIG. 2A-B. Thus, referring to FIG. 2A, a mobile phase
reservoir (1) is connected to a solvent delivery system (2) which
is connected to a sample injector (3) which is connected to one
port of a multiport valve (4). Other ports of the multiport valve
(4) are connected to a reservoir (i.e., a sample loop) (5), the
second opening of the column (6), a detector (7), and waste (8),
which is connected to an optional data integrator (not shown). The
sample loop connects to the first opening of the column (6).
[0058] During operation of the above system, mobile phase (1) is
supplied to the system using a solvent delivery system (2). Sample
is injected into the system with a sample injector (3), passed
through the multiport valve (4) set in the first position, through
the sample loop (5) and onto the monolithic column (6) under
conditions such that the analyte of interest is retained on the
column while large molecular weight species are swept off of the
column and through the detector (see FIG. 2A). The valve (4) is
then switched to the second position (see FIG. 2B), reversing the
flow of mobile phase through the column, and the analyte is eluted
from the column and into the sample loop (5). The valve (4) is
switched back to the first position (see FIG. 2A) and the analyte
is re-supplied to the column (6). The analyte may then be eluted
off the column under conditions sufficient to separate the analyte
or analytes of interest from each other or from other substances
retained on the column and detected using the detector (7).
[0059] In a preferred embodiment of the above aspect of the
invention, the system further comprises a second multiport valve,
preferably connected in tandem with the first multiport valve. Such
a system is set forth in FIG. 3A-C. Thus, referring to FIG. 3A, a
first mobile phase source (1) is connected to a solvent delivery
system (2), which is connected to a sample injector (3), which is
connected to one port (shown as port # 6) of a first multiport
valve (4). Other ports of the multiport valve (4) are connected to
a reservoir (i.e., sample loop) (5), the bottom end of the column
(6), and a second multiport valve (7). The second valve (7) is
further connected to waste (8) and a detector (9). The detector may
be further connected to an optional data integrator (not
shown).
[0060] During the operation of the above system, mobile phase (1)
is supplied to the system using solvent delivery system (2). Sample
is injected into the system with a sample injector (3), passed
through the first valve (4) set in first position through the
sample loop (5) and onto the monolithic column (6) under conditions
such that the analyte of interest is retained on the column while
large molecular weight species are swept off of the column, through
second valve (7) in the first position and into waste (8) (as shown
in FIG. 3A). The first valve (4) is switched to the second position
(as shown in FIG. 3B) and the analyte is eluted from the column and
into the sample loop (5). The first valve (4) is then switched back
to the first position (as shown in FIG. 3C) and the analyte is
resupplied to the column (6). The second valve (7) is switched to
the second position (as shown in FIG. 3C) so that flow of effluent
will pass through the detector (9) (see FIG. 3C). The analyte is
eluted off the column under conditions sufficient to separate the
analyte or analytes of interest from each other or from other
substances retained on the column.
[0061] Mobile Phase Supply
[0062] A mobile phase supply comprises a mobile phase source and a
solvent delivery system. Such a solvent delivery system is a
pumping device such as commercially available HPLC pumps, which
provide solvent or mobile phase to a column. Such pumps generally
provide pulse-free flows, flow rates ranging from 0.1-10 mL/min,
accurate control of flow rate, generation of high pressure (up to
6000 psi), and corrosion- and solvent-resistant components.
Reciprocating pumps consist of a small chamber into which the
solvent is pumped by the back and forth motion of a motor-driven
piston. Two check valves, which open and close alternately, control
the direction and flow of solvent in and out of a cylinder.
Single-piston pumps use specially designed cams to permit very
rapid refill times, producing a more continuous flow.
[0063] The disadvantage of pulsed flows with reciprocating pumps is
often overcome by using a pulse damper. The use of a dual-piston
pump, which operates with the pistons moving out of phase with each
other, offers a reasonable solution for pulse-free fluid
delivery.
[0064] A mobile phase "gradient" or "gradient elution" as used
herein refers to steady changes in the mobile phase composition
during a chromatographic run. The main purpose of gradient elution
is to elute analytes that are strongly retained by the column
faster, while having the weakly retained analytes eluted more
slowly so that eluted analytes produce well resolved peaks upon
detection. For example, in reversed phase chromatography, starting
with a low content of the organic solvent in the eluent allows the
weakly retained analytes to be separated. Strongly retained
analytes will remain on the adsorbent surface at the top of the
column, or will move very slowly. Increasing the amount of organic
component in the eluent (e.g., acetonitrile) allows strongly
retained components to move faster, because of the steady increase
of the competition for the adsorption sites by the organic
solvent.
[0065] Mobile phase gradients may be generated through high
pressure mixing, which requires a pump for each solvent, or low
pressure mixing which requires only one pump. In high-pressure
mixing systems, individual high pressure pumps are used to provide
each solvent. The outlet of each pump is either connected to a
mixing connector (usually referred to as a "T" since there are
normally two inlet lines and one outlet line) or to a mixing
chamber. Thus, the two solvents are blended en route to the
injector and column, that is, mixing is accomplished on the
high-pressure side of the pumps. The generation of a mobile phase
gradient created from three solvents may be accomplished by
utilizing three separate pumps. In low-pressure systems, mixing is
accomplished prior to the pump, at its low-pressure side and the
overall flow rate is controlled by a single pump. Proportioning
valves, normally solenoid operated, are used to deliver the
individual solvents. The controller simply divides the signal
according to the percentage of each component and each valve is
opened for the proper period of time. Usually the valves deliver
the individual solvents into a mixing chamber which then feeds the
blended solvent to the pump. In some systems, the valves feed the
mobile phase components through a mixing connector directly to the
high-pressure pump. Programmable flow rate control is desirable for
gradient generation by either method.
[0066] Sample Injector
[0067] A manual sample injector that is typically used comprises a
2-position valve that includes a fixed sample loop (e.g., 20 or 100
.mu.l). In one configuration, the valve is set so that the flow
from the pump is sent directly into the column; when the position
of the valve is switched, the flow from the pump is diverted
through the sample loop and into the column, thus supplying the
sample to the column. Valves with electrically or pneumatically
actuated position switches are commercially available and may be
used.
[0068] Automated sample injectors (i.e., autosamplers) may be used
in invention methods and systems. Such autosamplers can store and
sequentially inject multiple samples are useful in high-throughput
screening methods. Autosamplers are commercially available from a
variety of sources.
[0069] Multiport Valve
[0070] Multiport valves or reversing valves are available in many
configurations from many commercial sources. Such valves may have,
for example, six , or, eight, or ten, or more ports and up to six
positions. Such valves may be optionally controlled with an
actuator, allowing for automated control of the position of the
valve.
[0071] In one example, the multiport valve has 6 ports and two
operating positions. Thus, the valve may be connected
simultaneously to an injector (with a solvent delivery system
connected upstream), the top end of a column, the bottom end of a
column and a detector. The components may be configured so that the
multiport valve, which has two operating positions, controls the
direction of the flow of solvent through the column. In the first
position, solvent flows from the solvent delivery system, through
the sample injector, into the valve, through the sample loop and
into the top of the column. The solvent then flows through the
column, out of the bottom of the column and to the detector or
waste line. In the second position, solvent flows through the
solvent delivery system, into the valve, and into the bottom of the
column. The solvent then flows in the opposite direction through
the column, out of the top of the column and to the detector or
waste line.
[0072] In another example, a second valve may be connected in
tandem with the first valve. In this system, a solvent delivery
system is connected to a sample injector which is connected one
port of a multiport valve. The other ports of the multiport valve
are connected to the top end of the column (via a sample loop) and
the bottom end of the column, and to the second multiport valve.
The second multiport valve is further connected to one or more
detectors, or a detector and a waste line. The second valve,
therefore, controls the flow of effluent from the column to either
of one or more in-line detectors or waste. Thus, when the first
valve is in the first position, the injector is connected to the
valve which is connected to the sample loop which is connected to
the top end of the column. The bottom end of the column is
connected to the valve which is further connected to the second
valve. The second valve has two operating positions so that when
the second valve is in one position, the first valve is connected
(via the second valve) to a detector or, when the valve is in the
second position, to a waste line. An optional second detector may
replace the waste line. In another example, a second chromatography
column is connected to the second valve. In this system, the first
valve is connected (via the second valve) to the second column (and
to an optional downstream detector) or, when the valve is in the
second position, to a waste line.
[0073] Columns
[0074] A monolithic column comprises a "monolith," a continuous bed
consisting of a single piece of a highly porous solid material (see
e.g., Tennikova T B, Svec F (1993) J Chromatogr 646:279). A
distinguishing feature of this medium is that the mobile phase is
forced to flow through the large pores of the medium. As a
consequence, mass transport is enhanced by convection and has a
positive effect on the separation. Monolithic supports commercially
available include: silica gel based monolithic beds, polyacrylamide
based monolithic beds, and rigid organic gel based monolithic
beds.
[0075] Silica gel-based monolithic beds are solid rods of silica
monolith that have been prepared according to a sol-gel process.
This process is based on the hydrolysis and polycondensation of
alkoxysilanes in the presence of water-soluble polymers. The method
leads to "rods" made of a single piece of porous silica with a
defined bimodal pore structure having macropores (of about 2 .mu.m)
and mesopores (of about 0.013 .mu.m) when smaller rods intended for
analytical purposes are prepared. These columns have about 80%
porosity, which is 15% more than columns packed with standard
particulate packing (see e.g., Nakanishi K, Soga N (1991) J Am
Ceram Soc 74:2518; Cabrera K, Wieland G, Lubda D, Nakanishi K, Soga
N, Minakuchi H, Unger K K (1998) Trends Anal Chem 17:50).
[0076] Polyacrylamide-based monolithic beds are made of swollen
polyacrylamide gel compressed in the shape of columns. Such columns
rely on the polymerization of monomers and in the chromatographic
column. In the presence of salt, the polymer chains form aggregates
into large bundles by hydrophobic interaction, creating voids
between the bundles (irregularly shaped channels) large enough to
permit a high hydrodynamic flow. Following polymerization, the bed
is compressed by connecting it to an HPLC pump adjusted to a flow
rate equal or higher than that used in subsequent runs. The
resulting bed can be regarded as a rod or plug permeated by
channels through which the eluent can pass upon application of
pressure. The polymer chains form a dense, homogeneous network of
nodules consisting of microparticles with an average diameter of 2
.mu.m. The channels between the nodules are large enough to permit
a high hydrodynamic flow (see e.g., Hjerten S, Liao J-L, Zhang R
(1989) J Chromatogr 473:273; Liao J-L, Zhang R, Hjerten S (1991) J
Chromatogr 586:21).
[0077] Rigid organic gel-based monolithic beds are prepared by free
radical polymerization of a mixture of a polymerizable monomer,
optionally with functional groups, such as glycidyl methacrylate,
ethylene dimethacrylate, a crosslinking agent, a radical chain
initiator, such as 2,2'-azobisisobutyronitrile, and porogenic
solvents (cyclohexanol and dodecanol) in barrels of an appropriate
mold in the case of glycidyl methacrylate-co-ethylene
dimethacrylate (GMA-EDMA) monoliths (see e.g., Svec F, Tennikova T
B (1991) J Bioact Compat Polym 6:393; Svec F, Jelinkova M, Votavova
E (1991) Angew Macromol Chem 188:167; Svec F, Frechet J M J (1992)
Anal Chem 64:820). Another method uses free radical polymerization
of a mixture of styrene and divinylbenzene (as a cross-linking
reagent) using 2,2'-azobisisobutyronitrile as an initiator and
porogenic solvents (dodecanol and toluene) (Merhar M, J Liq
Chromatogr 24:2429 (2001)). After polymerization, the formed block
of polymer is washed, e.g. with methanol, followed by a
methanol-water mixture (50:50) and distilled water to remove
porogenes and residual monomers from the polymer. After this, the
monolithic bed is ready for derivatization to achieve a desired
chemistry or immobilization of ligands. GMA-EDMA monoliths have
active epoxide groups which can easily be further modified using
various chemicals, e.g. diethyl amine, propane sulfone for ion
exchange chromatography, e.g. butyl groups for hydrophobic
interaction chromatography and any desired protein ligand for
affinity chromatography. Alternatively, the epoxide groups
containing monolith material can be modified to obtain polar groups
on the surface, e.g. by using acids, e.g. sulfuric acid; to obtain
the monolith material in hydrolized form that carries OH groups.
Depending on the adsorption and elution conditions, a monolith
carrying polar groups, e.g. hydroxyl (OH) groups or amino
(NH.sub.2) groups, is suitable for being used in a variety of
adsorption principles, e.g. the so-called "normal phase"
chromatography (Dorsey J G, Foley J P, Cooper W T, Barford R A,
Barth H G (1990) Anal. Chem. 62:324 R) or the so-called
"hydrophilic interaction" chromatography (Alpert A J (1990) J.
Chromatogr. 499:17), the so-called "cohydration/cosovent exclusion
promoted chromatography" (Validated Biosystems: Purification Tools
for Monoclonal Antibodies, Cagnon P (1996), 103) or the so-called
"hydrogen bond chromatography" (Fujita T, Suzuki Y, Yamauti J,
Takagahara I, Fujii K., Yamashita J, Florio T (1980) J. Biochem.
(Tokyo), 87 (1):89).
[0078] A number of different columns are commercially available for
use in analytical chromatography. These columns differ in the
column packing material and thus, the means by which analytes are
retained and include reversed-phase or hydrophobic interaction, ion
exchange, size exclusion or gel permeation, and affinity columns.
Numerous column packings are available for analytical
chromatographic separation of samples, and selection of an
appropriate separation protocol is an empirical process that
depends on the sample characteristics, the analyte of interest, the
interfering substances present and their characteristics, etc. For
HPLC, polar, ion exchange (both cation and anion), hydrophobic
interaction, phenyl, C-2, C-8, and C-18 columns are commercially
available. During chromatography, the separation of materials is
effected by variables such as choice of eluant (also known as a
"mobile phase"), choice of gradient elution and the gradient
conditions, temperature, etc.
[0079] In reversed phase (RP) liquid chromatography, the typical
polar stationary phase is replaced with a hydrophobic stationary
phase, thus the phase is "reversed." A reversed-phase column, then,
retains hydrophobic analytes, which are eluted more readily as the
proportion of the hydrophobic component of the mobile phase is
increased. Exemplary columns include phenyl, C-2, C-4, C-8, and
C-18.
[0080] Affinity chromatography is based on selective non-covalent
interaction between an analyte and specific molecules. It is very
specific, but not very robust. It is often used in biochemistry in
the purification of proteins protein constructs (e.g., fusion
proteins, tagged proteins, and the like).
[0081] Detection and Identification of Analyte
[0082] In some embodiments, a mass spectrometer is used in-line for
detection and identification of the analyte.
[0083] The terms "mass spectrometry" or "MS" as used herein refer
to methods of filtering, detecting, and measuring ions based on
their mass-to-charge ratio, or "m/z." In general, one or more
molecules of interest are ionized, and the ions are subsequently
introduced into a mass spectrographic instrument where, due to a
combination of magnetic and electric fields, the ions follow a path
in space that is dependent upon mass ("m") and charge ("z"). See,
e.g. U.S. Pat. Nos. 6,204,500, entitled "Mass Spectrometry From
Surfaces;" U.S. Pat. No. 6,107,623, entitled "Methods and Apparatus
for Tandem Mass Spectrometry;" 6,268,144, entitled "DNA Diagnostics
Based On Mass Spectrometry;" 6,124,137, entitled "Surface-Enhanced
Photolabile Attachment And Release For Desorption And Detection Of
Analytes;" Wright et al., Prostate Cancer and Prostatic Diseases
2:264-76 (1999); and Merchant and Weinberger, Electrophoresis
21:1164-67 (2000), each of which is hereby incorporated by
reference in its entirety, including all tables, figures, and
claims.
[0084] For example, in a "quadrupole" or "quadrupole ion trap"
instrument, ions in an oscillating radio frequency field experience
a force proportional to the DC potential applied between
electrodes, the amplitude of the RF signal, and m/z. The voltage
and amplitude can be selected so that only ions having a particular
m/z travel the length of the quadrupole, while all other ions are
deflected. Thus, quadrupole instruments can act as both a "mass
filter" and as a "mass detector" for the ions injected into the
instrument.
[0085] Moreover, one can often enhance the resolution of the MS
technique by employing "tandem mass spectrometry," or "MS/MS." In
this technique, a first, or parent, ion generated from a molecule
of interest can be filtered in an MS instrument, and these parent
ions subsequently fragmented to yield one or more second, or
daughter, ions that are then analyzed in a second MS procedure. By
careful selection of parent ions, only ions produced by certain
analytes are passed to the fragmentation chamber, where collision
with atoms of an inert gas to produce these daughter ions. Because
both the parent and daughter ions are produced in a reproducible
fashion under a given set of ionization/fragmentation conditions,
the MS/MS technique can provide an extremely powerful analytical
tool. For example, the combination of filtration/fragmentation can
be used to eliminate interfering substances, and can be
particularly useful in complex samples, such as biological
samples.
[0086] Additionally, recent advances in technology, such as
matrix-assisted laser desorption ionization coupled with
time-of-flight analyzers ("MALDI-TOF") permit the analysis of
analytes at femtomole levels in very short ion pulses. Mass
spectrometers that combine time-of-flight analyzers with tandem MS
are also well known to the artisan. Additionally, multiple mass
spectrometry steps can be combined in methods known as
"MS/MS.sup.n." Various other combinations may be employed, such as
MS/MS/TOF, MALDI/MS/MS/TOF, or SELDI/MS/MS/TOF mass
spectrometry.
[0087] Ions can be produced using a variety of methods including,
but not limited to, electron ionization, chemical ionization, fast
atom bombardment, field desorption, and matrix-assisted laser
desorption ionization ("MALDI"), surface enhanced laser desorption
ionization ("SELDI"), photon ionization, electrospray ionization,
and inductively coupled plasma.
[0088] The term "electron ionization" as used herein refers to
methods in which an analyte of interest in a gaseous or vapor phase
is interacted with a flow of electrons. Impact of the electrons
with the analyte produces analyte ions, which may then be subjected
to a mass spectroscopy technique.
[0089] The term "chemical ionization" as used herein refers to
methods in which a reagent gas (e.g. ammonia) is subjected to
electron impact, and analyte ions are formed by the interaction of
reagent gas ions and analyte molecules.
[0090] The term "fast atom bombardment" as used herein refers to
methods in which a beam of high energy atoms (often Xe or Ar)
impacts a non-volatile test sample, desorbing and ionizing
molecules contained in the sample. Samples are dissolved in a
viscous liquid matrix, such as glycerol, thioglycerol,
m-nitrobenzyl alcohol, 18-crown-6 crown ether, 2-nitrophenyloctyl
ether, sulfolane, diethanolamine, and triethanolamine. The choice
of an appropriate matrix for a compound or sample is an empirical
process.
[0091] The term "field desorption" as used herein refers to methods
in which a non-volatile test sample is placed on an ionization
surface, and an intense electric field is used to generate analyte
ions.
[0092] The term "matrix-assisted laser desorption ionization," or
"MALDI" as used herein refers to methods in which a non-volatile
sample is exposed to laser irradiation, which desorbs and ionizes
analytes in the sample by various ionization pathways, including
photo-onization, protonation, deprotonation, and cluster decay. For
MALDI, the sample is mixed with an energy-absorbing matrix, which
facilitates desorption of analyte molecules.
[0093] The term "surface enhanced laser desorption ionization," or
"SELDI" as used herein refers to another method in which a
non-volatile sample is exposed to laser irradiation, which desorbs
and ionizes analytes in the sample by various ionization pathways,
including photo-ionization, protonation, deprotonation, and cluster
decay. For SELDI, the sample is typically bound to a surface that
preferentially retains one or more analytes of interest. As in
MALDI, this process may also employ an energy-absorbing material to
facilitate ionization.
[0094] The term "electrospray ionization" or ESI as used herein
refers to methods in which a solution is passed along a short
length of capillary tube, to the end of which is applied a high
positive or negative electric potential. Solution reaching the end
of the tube, is vaporized (nebulized) into a jet or spray of very
small droplets of solution in solvent vapor. This mist of droplets
flows through an evaporation chamber which is heated slightly to
prevent condensation and to evaporate solvent. As the droplets get
smaller the electrical surface charge density increases until such
time that the natural repulsion between like charges causes ions as
well as neutral molecules to be released.
[0095] The term "Atmospheric Pressure Chemical Ionization," or
"APCI," as used herein refers to methods that are similar to ESI;
however, APCI produces ions by ion-molecule reactions that occur
within aplasma at atmospheric pressure. The plasma is maintained by
an electric discharge between the spray capillary and a counter
electrode. Then ions are typically extracted into the mass analyzer
by use of a set of differentially pumped skimmer stages. A
counterflow of dry and preheated N2 gas may be used to improve
removal of solvent. The gas-phase ionization in APCI can be more
effective than ESI for analyzing less-polar species.
[0096] The term "inductively coupled plasma" as used herein refers
to methods in which a sample is interacted with a partially ionized
gas at a sufficiently high temperature to atomize and ionize most
elements.
[0097] The term "ionization" as used herein refers to the process
of generating an analyte ion having a net electrical charge equal
to one or more electron units. Negative ions are those ions having
a net negative charge of one or more electron units, while positive
ions are those ions having a net positive charge of one or more
electron units.
[0098] The term "operating in negative ion mode" refers to those
mass spectrometry methods where negative ions are detected.
Similarly, "operating in positive ion mode" refers to those mass
spectrometry methods where positive ions are detected.
[0099] The term "desorption" as used herein refers to the removal
of an analyte from a surface and/or the entry of an analyte into a
gaseous phase.
[0100] In those embodiments, such as MS/MS, where parent ions are
isolated for further fragmentation, collision-induced dissociation,
or "CID," is often used to generate the ion fragments for further
detection. In CID, parent ions gain energy through collisions with
an inert gas, and subsequently fragment by a process referred to as
"unimolecular decomposition." Sufficient energy must be deposited
in the parent ion so that certain bonds within the ion can be
broken due to increased vibrational energy.
[0101] In other embodiments, any of a variety of standard HPLC
detectors can be used for the detection of the analyte upon elution
from the analytical column. In this case, the elution of a compound
from the column is detected as a peak in a chromatogram. The
retention time of the peak is used to identify the compound, and
the peak height (or area) is proportional to the amount of the
compound in the sample. The "retention time" is the time required
for an analyte to pass through a chromatographic system and is
measured from the time of injection to the time of detection.
Ideally, each analyte of interest will have a characteristic
retention time. However, the retention of an analyte often differs
considerably between experiments and laboratories due to variations
of the eluent, the stationary phase, temperature, and the setup of
the chromatographic system. Therefore the retention time of the
test analyte is compared to that of one or more standard compounds
under identical conditions. An appropriate detector exhibits good
sensitivity, good stability, reproducibility, linear response over
a few orders of magnitude, short response time, and ease of
operation. Such detectors include, but are not limited to, UV/Vis
absorbance detectors, photodiodearray detectors, fluorescence
detectors, refractive index detectors, and conductivity
detectors.
[0102] UV/Vis absorbance detectors consisting of a scanning
spectrophotometer with grating optics can be used. The independent
or combined use of a Deuterium source (UV range, 190-360 nm) with a
Tungsten source (visible range, 360-800 nm) provides a simple means
of detecting absorbing species as they emerge from the column.
[0103] Photodiode-array (PDA)-based instruments are UV/Vis
absorbance detectors that permit very rapid collection of data over
a selected spectral range. Absorbance spectral data for each
chromatographic peak can be collected and stored. Stored data may
be compared with the spectrum of a pure standard from a library.
The PDA detector is useful in the identification of components that
are difficult to resolve (overlapping peaks) since the
characteristic spectrum for each of the unresolved components is
likely to be different.
[0104] Fluorescence detectors are useful in the detection of
analytes that exhibit a chemiluminescent property such as
fluorescence or phosphorescence. They are more sensitive than UV
absorbance detectors by at least one order of magnitude.
Fluorescence is typically observed by detection of the
grating-isolated emission radiation at a 90-degree angle to the
excitation beam. The number of fluorescing species can be enhanced
by a post-column derivatization (PCD) reaction of the eluted
compounds (or pre-column derivatization reaction of the sample
itself) with special reagents.
[0105] Refractive index (RI) detectors respond to nearly all
solutes. The difference in the refractive index of the reference
mobile phase versus the column effluent results in the detection of
separated components as peaks on the chromatogram. Because of its
extreme sensitivity to the mobile phase, this detector may not be
used without adequate pulse-damping within the LC pump, nor is it
suitable for gradient applications because of the changing mobile
phase composition. The detection limits are usually lower than
those observed with absorbance detectors.
[0106] Conductivity detectors provide high-sensitivity detection of
all charged species. This detector may be used with an HPLC system
for the simple and reliable quantification of anions, cations,
metals, organic acids, and surfactants down to the ppb level. The
addition of a chemical suppressor between the column and
conductivity detector serves to reduce the eluant conductivity,
allowing the use of gradient elution and the determination of ppb
levels with minimum baseline drift. For a typical determination of
low levels of anions, the eluant is converted to its weakly ionized
low-conductivity acid (e.g., Na2CO3 to carbonic acid), reducing the
background noise. At the same time, the analyte anions are
converted to their corresponding high-conductivity acids (e.g.,
NaCl to HCl), increasing the relative analyte signal.
[0107] Data Collection
[0108] A record of the detector response may be obtained using a
chart recorder or an integrator. Automated data and method storage,
data processing, and reporting can be performed with standard
PC-based data collection packages.
EXAMPLE 1
[0109] A sample of serum was assayed for estradiol using a
monolithic column for preparative chromatography followed by
in-line analytical chromatography using a second column.
[0110] An HTLC system was used which comprised two LC pumps
(quaternary pump or binary), two multiport valves, a monolithic C18
column (50.times.4.6 mm, mesopore 130 .ANG., macropore 2 .mu.m,
porosity>80%), an ether-linked phenyl phase column
(100.times.2.0 mm, 80 .ANG., 4 .mu.m), a 100 .mu.L sample loop, and
a mass spectrometer ("ms"). The system was configured as shown in
FIG. 7A-C.
[0111] The first pump was connected to port 2 of the first
multiport valve, the 100 .mu.L sample loop was connected to ports 3
and 4, and the first column (the monolithic C18 column) was located
between ports 1 and 5. The second multiport valve was connected,
via port 3, to the first multiport valve at port 6. The second
valve was further connected to the second column (the ether-linked
phenyl phase column), which was further connected to a mass
spectrometer ("MS") via port 4, and a waste line via port 2.
[0112] The solvents used were as follows: [0113] Solvent A: 0.1%
formic acid [0114] Solvent B: 100% methanol
[0115] The samples were processed by adding 200 .mu.L of serum and
diluting with 300 .mu.L of 20% formic acid in water and adding 25
.mu.L of the internal standard in methanol. The columns were
equilibrated with both multiport valves in the "LOAD" position (see
FIG. 7A) using 100% solvent A from the first pump. 80 .mu.L of the
processed sample was injected onto the column using 100% solvent A
at a flow rate of 4-5 mL/min for 30 seconds. The first multiport
valve was switched to the "ELUTE" position (see FIG. 7B) and the
column was backflushed with 100% solvent B from the first pump at a
flow rate of 1 mL/min for 60 seconds to elute retained analytes
from the column into the 200 .mu.L sample loop. The second
multiport valve was switched to the "ELUTE" position (see FIG. 7C)
and the eluted analytes were applied to the second column using 95%
solvent A: 5% solvent B from the first pump at a flow rate of 1
mL/min for 15 seconds. The second multiport valve was switched to
the "LOAD" position (see FIG. 7B) and the analytes were eluted with
a gradient of 95% solvent A: 5% solvent B to 100% solvent B
generated by the second pump and run at a flow rate of 1.6 mL/min
over 200 seconds. Eluted analytes were detected using the in-line
mass spectrometer. A peak corresponding to a retention time of 2.48
minutes was observed and determined to be estradiol. D8-estradiol,
run as an internal standard, exhibited a retention time of 2.48
minutes. The resulting chromatograms are shown in FIG. 6.
[0116] To recharge the column for subsequent samples, the first
column was backflushed with 100% solvent B from the first pump at a
flow rate of 4-5 mL/min for 60 seconds with the first multiport
valve in the "ELUTE" position and the second multiport valve in the
"LOAD" position (see FIG. 7B). The first multiport valve was
switched to the "LOAD" position (see FIG. 7A) and the column was
equilibrated with 100% solvent A from the first pump at a flow rate
of 5 mL/min for 40 seconds.
EXAMPLE 2
[0117] A sample of serum was assayed for estradiol using a single
monolithic column for both preparative chromatography and
analytical chromatography.
[0118] An HTLC system was used which comprised a quaternary pump,
two multiport valves, a monolithic C18 column (50.times.4.6 mm,
mesopore 130 .ANG., macropore 2 .mu.m, porosity>80%), a 100
.mu.L sample loop, a 200 .mu.L sample loop, and a mass
spectrometer. The system was connected as in FIG. 4A-C. The
quaternary pump (not shown) was connected to port 2 of the first
multiport valve, the 100 .mu.L sample loop was connected to ports 3
and 4, and the 200 .mu.L sample loop was connected between port 5
and the column. The second multiport valve was connected, via port
3, to the first multiport valve at port 6. The second valve was
further connected to a mass spectrometer ("MS") via port 4 and a
waste line via port 2.
[0119] The solvents used were as follows: [0120] Solvent A: 0.1%
formic acid [0121] Solvent B: 100% methanol
[0122] A sample of serum was diluted in solvent A. The column was
equilibrated with both multiport valves in the "LOAD" position (see
FIG. 4A) using 100% solvent A. 50 .mu.L of the diluted sample was
injected onto the column using 100% solvent A at a flow rate of 5
mL/min for 35 seconds. The first multiport valve was switched to
the "ELUTE" position (see FIG. 4B) and the column was backflushed
with 100% solvent B at a flow rate of 1 mL/min for 60 seconds to
elute retained analytes from the column and into the 200 .mu.L
sample loop. The first multiport valve was switched to the "LOAD"
position and the second multiport valve was switched to the "ELUTE"
position (see FIG. 4C) and the eluted analytes were reapplied to
the column using 95% solvent A: 5% solvent B at a flow rate of 1
mL/min for 15 seconds. The analytes were eluted with a gradient of
95% solvent A: 5% solvent B to 100% solvent B at a flow rate of 1.6
mL/min over 200 seconds and detected using the in-line mass
spectrometer. A peak corresponding to a retention time of 2.48
minutes was observed and determined to be estradiol. D8-estradiol
was run as a separate sample for use as an internal standard and
exhibited a retention time of 2.48 minutes. The resulting
chromatograms are shown in FIG. 6.
[0123] To recharge the column for subsequent samples, the first
multiport valve was switched to the "ELUTE" and the second
multiport valve switched to the "LOAD" position and the column was
backflushed with 100% solvent B at a flow rate of 5 mL/min for 60
seconds. The first multiport valve was switched to the "LOAD"
position and the column was equilibrated with 100% solvent A at a
flow rate of 5 mL/min for 40 seconds.
[0124] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs.
[0125] The inventions illustratively described herein may suitably
be practiced in the absence of any element or elements, limitation
or limitations, not specifically disclosed herein. Thus, for
example, the terms "comprising", "including," containing", etc.
shall be read expansively and without limitation. Additionally, the
terms and expressions employed herein have been used as terms of
description and not of limitation, and there is no intention in the
use of such terms and expressions of excluding any equivalents of
the features shown and described or portions thereof, but it is
recognized that various modifications are possible within the scope
of the invention claimed.
[0126] Thus, it should be understood that although the present
invention has been specifically disclosed by preferred embodiments
and optional features, modification, improvement and variation of
the inventions embodied therein herein disclosed may be resorted to
by those skilled in the art, and that such modifications,
improvements and variations are considered to be within the scope
of this invention. The materials, methods, and examples provided
here are representative of preferred embodiments, are exemplary,
and are not intended as limitations on the scope of the
invention.
[0127] The invention has been described broadly and generically
herein. Each of the narrower species and subgeneric groupings
falling within the generic disclosure also form part of the
invention. This includes the generic description of the invention
with a proviso or negative limitation removing any subject matter
from the genus, regardless of whether or not the excised material
is specifically recited herein.
[0128] In addition, where features or aspects of the invention are
described in terms of Markush groups, those skilled in the art will
recognize that the invention is also thereby described in terms of
any individual member or subgroup of members of the Markush
group.
[0129] All publications, patent applications, patents, and other
references mentioned herein are expressly incorporated by reference
in their entirety, to the same extent as if each were incorporated
by reference individually. In case of conflict, the present
specification, including definitions, will control.
[0130] Other embodiments are set forth within the following
claims.
* * * * *