U.S. patent application number 10/015668 was filed with the patent office on 2003-06-19 for liquid chromatograph mass spectrometer.
This patent application is currently assigned to SHIMADZU CORPORATION. Invention is credited to Yamamoto, Yoshitake.
Application Number | 20030113936 10/015668 |
Document ID | / |
Family ID | 27806826 |
Filed Date | 2003-06-19 |
United States Patent
Application |
20030113936 |
Kind Code |
A1 |
Yamamoto, Yoshitake |
June 19, 2003 |
Liquid chromatograph mass spectrometer
Abstract
In a liquid chromatograph mass spectrometer, chromatogram data
is obtained by carrying out alternately a mass scanning in a
positive ion detection mode and a mass scanning in a negative ion
detection mode, obtaining the chromatogram data in every positive
and negative polarities through summing up the mass spectrum data
obtained at the respective mass scannings, and adding the data of
both polarities. Since the chromatograms in both polarities are
averaged, even if there is a level difference therebetween, a
chromatogram in a normal form can be obtained.
Inventors: |
Yamamoto, Yoshitake;
(Otokuni-gun, JP) |
Correspondence
Address: |
KANESAKA AND TAKEUCHI
1423 Powhatan Street
Alexandria
VA
22314
US
|
Assignee: |
SHIMADZU CORPORATION
|
Family ID: |
27806826 |
Appl. No.: |
10/015668 |
Filed: |
December 17, 2001 |
Current U.S.
Class: |
436/173 ;
210/198.2; 210/656; 250/281; 422/70; 436/161; 73/61.52;
73/61.58 |
Current CPC
Class: |
G01N 30/7233 20130101;
G01N 30/8631 20130101; G01N 30/7293 20130101; G01N 2030/027
20130101; G01N 30/8624 20130101; Y10T 436/24 20150115; G01N 30/8641
20130101; G01N 2030/626 20130101; H01J 49/04 20130101 |
Class at
Publication: |
436/173 ;
436/161; 422/70; 210/656; 210/198.2; 250/281; 73/61.52;
73/61.58 |
International
Class: |
G01N 030/02; G01N
024/00 |
Claims
What is claimed is:
1. A chromatograph mass spectrometer for sequentially processing a
sample, comprising: a setting device for setting beforehand a
plurality of spectrometry conditions when a mass spectrometry is
carried out, a spectrometry execution device electrically connected
to the setting device for executing a cycle of spectrometries by
changing one of the spectrometry conditions set by the setting
device whenever one mass scanning in said cycle is carried out,
said spectrometry execution device sequentially executing the one
cycle spectrometries repeatedly, and an operation device
electrically connected to the spectrometry execution device for
obtaining chromatogram data by respectively adding together a
number of mass spectrum data obtained by the one mass scanning in
one cycle when one cycle of the mass spectrometry is completed.
2. A chromatograph mass spectrometer according to claim 1, further
comprising an introducing section for introducing the sample, a
chromatograph portion connected to the introducing section f or
separating components in the sample along a passage of time, a mass
spectrometry portion connected to the chromatograph portion f or
analyzing the components, and a fraction collector connected to the
chromatograph portion for collecting the respective components
based on information obtained in the mass spectrometry portion.
3. A chromatograph mass spectrometer according to claim 2, further
comprising a fraction control device electrically connected to the
operation device for controlling an operation of the fraction
collector based on the chromatogram data obtained by the operation
device.
4. A chromatograph mass spectrometer according to claim 3, wherein
said operation device adds the chromatogram data at the one mass
scanning with an added value in another mass scanning.
5. A chromatograph mass spectrometer according to claim 3, wherein
said operating device obtains the chromatogram data by adding the
mass spectrum data with respect to a specific mass number obtained
by each mass scanning.
6. A chromatograph mass spectrometer according to claim 1, wherein
said mass spectrometer is a liquid chromatograph mass spectrometer.
Description
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
[0001] The invention relates to a liquid chromatograph mass
spectrometer, in particular, an. apparatus suitable for
fractionating various components contained in a sample solution by
using a liquid chromatograph mass spectrometer.
[0002] Heretofore, there has been known a fraction chromatograph
wherein a plurality of components contained in a sample is
separated and collected by using a chromatograph device, such as
high performance liquid chromatograph (hereinafter referred to as
"HPLC").
[0003] FIG. 5 is a block diagram for showing an example of a
structure of a fraction chromatograph using HPLC. An eluant, i.e.
mobile phase, stored in an eluant tank 1 is sucked by a pump 2 and
is transferred to flow into a column 4 through a sample
introduction portion 3 at a predetermined flow rate. A sample
solution injected into the mobile phase at the sample introduction
portion 3 is introduced into the column 4 together with the mobile
phase, and while passing through the column 4, its components are
separated and eluted. A detector 5 detects sequentially the
components eluted from the column 4 and sends detection signals to
a signal process portion 6. All or a part of the eluate passing
through the detector 5 is introduced into a fraction collector 8.
The signal process portion 6 prepares a chromatogram based on the
detection signals obtained from the detector 5, and a control
portion 7 provides the fraction collector 8 with a control signal
for fraction based on a peak appearing on the chromatogram at real
time. The fraction collector 8 controls an electromagnetic valve
and the like based on the control signal and distributes the
eluates to vials corresponding to the respective components.
[0004] By the way, recently, there has been widely used a liquid
chromatograph mass spectrometer (hereinafter referred to as
"LC/MS") using a mass spectrometer (hereinafter referred to as
"MS") as a detector of HPLC. In MS, since various components
contained in an introduced sample are separated and detected in
every mass number, i.e. mass/charge, even if a plurality of
components is timewise overlapped, there is an advantage such that
these components are separated and subjected to a qualitative
analysis and a quantitative analysis.
[0005] In the LC/MS, a mass spectrum can be obtained by carrying
out a mass scanning over a set mass region, sequentially detecting
strengths of ions separated in every mass number and examining a
relationship between the mass number and the strength. Also, a
total ion chromatogram (hereinafter referred to simply as
"chromatogram") can be obtained by repeatedly carrying out the mass
scannings, integrating the ion strength in every scanning
regardless of the mass number and examining a timewise change of
the total ion strength. Further, by watching a specific mass
number, a mass chromatogram can be obtained by examining a timewise
change of the strengths of ions having the mass number in every
scanning.
[0006] In case the LC/MS, as described above, is used for the
fraction chromatograph, it is necessary to determine a timing of
fraction based on the chromatogram data for preparing a
chromatogram or mass chromatogram. Normally, the chromatogram data
is calculated according to process conditions set beforehand (for
example, strengths of ions having a specific mass number are added,
strengths of ions in a predetermined mass region are added and the
like), from a great number of mass spectrum data obtained by
one-time mass scanning. Thus, a chromatogram data can be obtained
in every mass scanning. Therefore, for example, in case a
spectrometry is carried out while alternatively changing a mass
scanning in a positive ion detection mode for detecting positive
ions and a mass scanning in a negative ion detection mode for
detecting negative ions, a chromatogram data obtained at a certain
time point t is a value calculated based on the mass spectrum
obtained by the positive ion detection mode, and the subsequent
chromatogram datum obtained at t+.DELTA.t is a value calculated
based on the mass spectrum obtained by the negative ion detection
mode.
[0007] Generally, since the levels of the background noises in the
positive ion detection mode and the negative ion detection mode are
different, the chromatogram prepared based on the mass spectrum
obtained in the positive ion detection mode and the chromatogram
prepared based on the mass spectrum obtained in the negative ion
detection mode are different in levels of the base lines as shown
in FIG. 6(a). Therefore, when the chromatogram data obtained when
the positive polarity and the negative polarity are switched over
as described above is connected or added in time sequence, the
chromatogram curve having sawteeth shapes as shown in FIG. 6(b) is
obtained. Also, in case a component detectable only by the positive
ion detection mode and a component detectable only by the negative
ion detection mode are mixed, since the respective chromatograms
become, for example, as shown in FIG. 7(a), when the chromatogram
data obtained when the positive polarity and the negative polarity
are switched over are connected or added in time sequence, the peak
waveform becomes sawteeth shapes as shown in FIG. 7(b).
[0008] In either case, in the control portion 7, since an accurate
starting point and an accurate terminal point of the peak can not
be determined by using such chromatogram data, it is impossible to
determine the timing of fractionating the respective components, or
an erroneous control signal is sent to the fraction collector 8. In
view of the defects as described above, in case the fraction
operation is carried out by the conventional LC/MS, since the
fraction operation can not be carried out while alternately
changing the positive polarity and the negative polarity, it is
necessary that the fraction operation in the positive ion detection
mode and the fraction operation in the negative ion detection mode
are separately carried out. Thus, the fraction operation is not
carried out effectively.
[0009] In view of the above problems, the present invention has
been made and an object of the present invention is to provide a
liquid chromatograph mass spectrometer, wherein even in case a mass
spectrometry is carried out while changing the spectrometry
conditions, such as alternately changing a positive polarity and a
negative polarity, a chromatogram for normally operating a fraction
collector can be obtained, so that a proper fraction operation can
be done by only one-time spectrometry.
[0010] Further objects and advantages of the invention will be
apparent from the following description of the invention.
SUMMARY OF THE INVENTION
[0011] In order to solve the above-stated problems, according to
the present invention, in a liquid chromatograph mass spectrometer,
a sample, components of which are separated in a liquid
chromatograph portion in a time-wise direction, i.e. along a
passage of time, is introduced into a mass spectrometry portion and
a fraction collector, and the fraction collector fractionates and
collects the respective components based on the information
obtained in the mass spectrometry portion. The liquid chromatograph
mass spectrometer includes: a setting device for setting beforehand
a plurality of spectrometry conditions when a mass spectrometry is
carried out; a spectrometry execution device for executing a cycle
of spectrometry by changing the spectrometry condition set by the
setting device whenever one-time mass scanning in one cycle is
carried out, the periodical spectrometry being repeated
sequentially; an operation device for obtaining chromatogram data
by adding together a number of mass spectrum data obtained by the
one-time mass scanning whenever the cycle of spectrometry is
completed and further adding thereto values in the respective mass
scannings, or for obtaining the chromatogram data by adding the
mass spectrum data with respect to a specific mass number obtained
by the respective mass scannings; and a fraction control device for
controlling an operation of the fraction collector based on the
chromatogram data obtained by the operation device.
[0012] Here, the "spectrometry condition" means a condition which
has an effect on the ion generating condition or the ion detecting
condition. For example, the spectrometry condition may include a
positive ion detection mode for detecting a positive ion and a
negative ion detection mode for detecting a negative ion. When the
positive ion detection mode and the negative ion detection mode are
set by the setting device, the spectrometry execution device
carries out alternately one-time mass scanning of the positive ion
detection mode and one-time mass scanning of the negative ion
detection mode. Since a large number of mass spectrum data with
respect to the mass number in a predetermined region can be
obtained by the respective mass scannings, the operation device
adds the mass spectrum data in each polarity, and further adds
thereto the values of the respective polarities to obtain a single
chromatogram. More specifically, since the single chromatogram
reflects a plurality of mass spectrum data of both polarities, even
if the levels on the base lines of the respective chromatograms of
the positive and negative ions are different, or a peak is present
only in either the positive ion or negative ion chromatogram, they
are averaged.
[0013] Incidentally, in case a fraction operation is carried out
based on the mass chromatogram, the operation device adds the mass
spectrum data with respect to a specific mass number obtained by
each mass scanning to obtain the chromatogram data.
[0014] According to the liquid chromatograph mass spectrometer of
the present invention, even in case the mass scanning is carried
out while changing the spectrometry conditions of the mass
spectrometry, there can be obtained a chromatogram wherein the peak
waveform can be normally obtained, so that the fractions of the
respective components can be properly carried out by the fraction
collector. Also, for example, since the fraction operations with
respect to the components of both polarities can be carried out by
a single spectrometry, it is not necessary to carry out fraction
operations for the respective polarities as in the conventional
liquid chromatograph mass spectrometer, thus shortening the time
required for the fraction operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a block diagram for showing an entire structure of
LC/MS of an embodiment according to the present invention;
[0016] FIG. 2 is a graphic chart for explaining a signal process
operation of the present embodiment;
[0017] FIG. 3 is a flow chart for showing the signal process
operation of the present embodiment;
[0018] FIGS. 4(a) and 4(b) are examples of chromatograms obtained
in the present embodiment;
[0019] FIG. 5 is a block diagram for showing a structure of a
fraction chromatograph using a general HPLC;
[0020] FIGS. 6(a) and 6(b) are chromatograms for explaining
problems in a fraction device using a conventional LC/MS; and
[0021] FIGS. 7(a), 7(b) are other chromatograms for explaining
problems in a fraction device using a conventional LC/MS.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Hereunder, LC/MS of an embodiment of the present invention
will be explained with reference to FIG. 1 to FIG. 4(b).
[0023] FIG. 1 is a block diagram of an entire LC/MS according to
the present embodiment. A sample liquid eluted from a column 4 of
an LC is divided into two-flow paths at a predetermined ratio at a
flow-path diverging portion 9, one of which is sent to an MS
portion 10 and the other of which is sent to a fraction collector
8. The MS portion 10 includes a nebulizing or atomizing chamber 11
having a nozzle 12 and a discharge electrode 13, and a spectrometry
chamber 16 having a quadrupole filter 17 and an ion detector 18.
There are provided two intermediate chambers 15 between the
nebulizing chamber 11 and the spectrometry chamber 16. The
nebulizing chamber 11 and the first intermediate chamber 15 are
connected through a desolvent pipe 14. The signal detected by the
ion detector 18 in the MS portion 10 is inputted into a signal
process portion 20, and, after being subjected to processing as
described later at the signal process portion 20, gives the
chromatogram data to a control portion 21. The control portion 21
controls operations of the respective portions in the MS portion
10, the fraction collector 8, and operations of the respective
portions of the LC though control signal lines are not shown,.
[0024] Operations of the MS portion 10 are as follows. When the
sample solution supplied from the column 4 reaches the nozzle 12,
the sample solution is atomized in the nebulizing chamber 11 as
high temperature drops. The dispersed drops collide with gas
molecules under the atmospheric pressure, are smashed into further
fine drops, and quickly dried, i.e. removal of the solvent, to
thereby vaporize the sample molecules. The fine gas particles
contact the buffer ions produced by the corona discharge from the
discharge electrode 13 to cause a chemical reaction, and ionized.
The fine drops containing the generated ions plunge into the
desolvent pipe 14 and are further subjected to the desolvent while
the fine drops pass through the desolvent pipe 14. The ions are
sent to the spectrometry chamber 16 through the two intermediate
chambers 15, and only objective ions having a specific mass number,
i.e. mass/charge, pass through the quadrupole filter 17 disposed in
the spectrometry chamber 16 to reach the ion detector 18. Electric
current corresponding to the ion number which has arrived at the
ion detector 18 can be taken out therefrom.
[0025] In the MS portion 10, a positive ion detection mode for
detecting the positive ions by generating the positive ions and a
negative ion detection mode for detecting the negative ions by
generating the negative ions can be switched over in a short time,
by changing voltages applied to the respective portions, such as
the discharge electrode 13, and switching the operation of the ion
detector 18.
[0026] Hereunder, operations of the present LC/MS when fraction
operations are carried out in both positive and negative polarities
alternately will be explained.
[0027] FIG. 3 is a flow chart for showing operations at the time of
the spectrometry in the signal process portion 20 and the control
portion 21, and FIG. 2 is a graphic chart for explaining the
operations thereof. An operator inputs various parameters, such as
operation conditions of LC, operation conditions of the MS portion
10 and process conditions in the signal process portion 20, to set
therein from the operating portion 22. These conditions include a
mass region at a time of mass scanning, a mass step, a scanning
time and so on in the MS portion 10.
[0028] When the spectrometry starts, first, the control portion 21
sets parameters of the respective portions of the MS portion 10 to
be the positive ion detection mode (Step S1), and carries out the
mass scanning in a predetermined mass region (Step S2). At the time
of the mass scanning, when the voltage applied to the quadrupole
filter 17 is controlled, the mass number of the ions having passed
through the quadrupole filter 17 and arrived at the ion detector 18
is changed. The signal process portion 20 processes the detection
signals which are sequentially changed at the time of the mass
scanning, and obtains the mass spectrum data for showing
relationships between the mass number and the ion strength (Step
S3). The mass spectrum reflects only the positive ion strength as
shown in FIG. 2. Among a large number of mass spectrum data, the
mass spectrum data is extracted according to the predetermined
process conditions, such as mass region, and is added together to
obtain chromatogram data A(+) of the positive polarity and stored
in a memory (Step S4).
[0029] Then, the control portion 21 sets parameters of the
respective portions of the MS portion 10 to become the negative ion
detection mode (Step S5), and carries out the mass scanning in a
predetermined mass region (Step S6). More specifically, the control
portion 21 carries out the mass scanning in the same manner as in
the above-explained positive ion detection mode, and the signal
process portion 20 processes the detection signals which are
sequentially changed at the time of mass scanning to obtain the
mass spectrum data showing relationships between the mass number
and the ion strength (Step S7). The mass spectrum reflects only the
negative ion strength as shown in FIG. 2. Among a large number of
mass spectrum data, the mass spectrum data is extracted according
to the predetermined process conditions, and is added together to
obtain chromatogram data A(-) of the negative polarity (Step S8).
Then, when the chromatogram data A(+) and A(-) of the positive and
negative polarities are completed, both data is added together to
obtain the chromatogram data A and outputted as an analogue value
(Step S9). Thereafter, until spectrometries of all components are
completed, the above-described processes are repeated by returning
from Step S10 to Step S.
[0030] With the above-described process, as shown in FIG. 2, a
chromatogram datum A can be obtained in every two times of the mass
scannings (one for the positive polarity and one for the negative
polarity). FIGS. 4(a) and 4(b) are chromatograms prepared based on
the chromatogram data obtained from the signal process portion 20.
According to the present LC/MS, even in case the chromatograms of
the positive and negative polarities are separately prepared and
the respective peaks are formed in different positions as shown in
FIG. 4(a), the peaks of both polarities appear on the chromatogram
in a normal form as shown in FIG. 4(b), and the sawteeth shapes as
shown in FIG. 7(b) are not formed.
[0031] When the control portion 21 receives the chromatogram data
from the signal process portion 20 at a real time, the control
portion 21 detects a starting point of a peak of an objective
component to be fractionated and outputs a collection start signal
to the fraction collector 8 with a predetermined time delay from
the time when the starting point is detected. The time delay is
determined by a flow rate of a mobile phase and pipe capacities
from the flow path diverging portion 9 to the nozzle 12 of the MS
portion 10 and from the flow path diverging portion 9 to an
electromagnetic valve of the fraction collector 8. In the fraction
collector 8, when the objective component arrives at the
electromagnetic valve, the electromagnetic valve is opened
according to the collecting start signal to start fraction. When a
termination point of the peak of the objective component is
detected, the control portion 21 sends a collection completion
signal to the fraction collector 8 in the same manner. Thus, when
the fraction or separation of the objective component is completed,
the electromagnetic valve is closed. In case a plurality of
components is fractionated, during a period when the
electromagnetic valve is closed, a vial bottle is moved by a
biaxial arm or the like and an empty vial bottle is set at a
fractioning position for the next fraction.
[0032] Incidentally, in case a spectrometry is carried out by using
only one polarity without changing the positive polarity and the
negative polarity as described above, either the chromatogram datum
A(+) or chromatogram datum A(-) in FIG. 3 may be processed as
zero.
[0033] While the above embodiment shows the case where the positive
polarity and the negative polarity are changed, in addition to
this, the same method can be used by changing or shifting the
operation conditions of the various mass spectrometries. For
example, it is possible to carry out the respective mass
spectrometries through change of a mode for cleavage of ions by
changing a voltage to be applied to a deflector electrode disposed
in the intermediate chamber of the MS portion 10. Of course, in
case the operation conditions include more than three kinds,
chromatogram data may be calculated in every mass spectrometries of
more than three times corresponding to the operation
conditions.
[0034] While the invention has been explained with reference to the
specific embodiments of the invention, the explanation is
illustrative and the invention is limited only by the appended
claims.
* * * * *