U.S. patent number 3,865,548 [Application Number 05/338,358] was granted by the patent office on 1975-02-11 for analytical apparatus and process.
This patent grant is currently assigned to Albert Einstein College of Medicine of Yeshiva University. Invention is credited to Jacques Padawer.
United States Patent |
3,865,548 |
Padawer |
February 11, 1975 |
Analytical apparatus and process
Abstract
A low load analytic system is proposed, comprising a cuvette
divided into separate chambers by a porous barrier which may be
free to move inside the cuvette, and a test reagent in one
compartment. The barrier may be floating on the reagent. The
barrier may be microporous or be a semipermeable membrane,
hydrophobic or hydrophilic, depending on the test. In one mode, the
cuvette is the barrel of a hypodermic syringe and the test reagent
is held in the far compartment, in the barrel of the syringe.
Numerous modifications of the system are also disclosed.
Inventors: |
Padawer; Jacques
(Hastings-on-Hudson, NY) |
Assignee: |
Albert Einstein College of Medicine
of Yeshiva University (Bronx, NY)
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Family
ID: |
26949070 |
Appl.
No.: |
05/338,358 |
Filed: |
March 5, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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262183 |
Jun 13, 1972 |
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Current U.S.
Class: |
436/165; 422/408;
356/246; 435/808; 436/68; 436/99; 436/116; 436/122; 436/133;
436/178; 422/913; 435/288.2 |
Current CPC
Class: |
A61B
5/150099 (20130101); A61B 5/150389 (20130101); A61B
10/0045 (20130101); B01L 3/5082 (20130101); A61B
5/153 (20130101); A61B 5/150717 (20130101); A61B
5/150236 (20130101); G01N 33/492 (20130101); A61B
5/145 (20130101); A61B 5/15003 (20130101); A61B
5/150755 (20130101); A61B 5/150244 (20130101); A61B
5/150519 (20130101); A61B 5/150213 (20130101); A61B
5/150587 (20130101); Y10T 436/255 (20150115); Y10T
436/186 (20150115); Y10S 435/808 (20130101); Y10T
436/148888 (20150115); Y10T 436/177692 (20150115); Y10T
436/204998 (20150115) |
Current International
Class: |
A61B
5/00 (20060101); A61B 5/15 (20060101); A61B
10/00 (20060101); B01L 3/14 (20060101); G01n
001/10 (); G01n 031/00 (); G01n 033/16 () |
Field of
Search: |
;23/23R,23B,253R,259,292,254R ;206/47R,219 ;356/246 ;195/127,139
;128/2F |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Searcy, "Diagnostic Biochemistry," p. 274 (1969)..
|
Primary Examiner: Scovronek; Joseph
Attorney, Agent or Firm: Bierman & Bierman
Parent Case Text
This application is a continuation-in-part of copending application
Ser. No. 262,183 filed June 13. 1972, now abandoned.
Claims
I claim:
1. An apparatus adapted for chemical analysis comprising a cuvette
having therein a first porous barrier which serves to
compartmentalize said cuvette, and a first test reagent fluid in a
first reagent compartment in the cuvette, said barrier being in
direct contact therewith, a second porous barrier and a second test
reagent fluid being present, the second test reagent being disposed
in a second compartment on the side of said second barrier away
from said first reagent compartment, the second barrier being in
direct contact with the two test reagents.
2. The apparatus of claim 1 wherein said porous barriers are
maintained in an axially spaced-apart relationship by at least one
spacer extending from said first barrier to said second
barrier.
3. The apparatus of claim 2 wherein said spacer comprises a hollow
tube.
4. The apparatus of claim 3 wherein there is provided a generally
cylindrical sled surrounding at least part of said tube, said sled
having at least one sealing portion disposed circumferentially
around said sled and adapted to substantially seal against the
inner wall of said cuvette.
5. An apparatus adapted for chemical analysis comrising a cuvette
having therein a first porous barrier which serves to
compartmentalize said cuvette, and a first test reagent fluid in a
first reagent compartment in the cuvette, said barrier being in
direct contact therewith, said cuvette having at least one lens
located in an area through which test results are sensed, said
cuvette having a curvature in said area, said lens compensating for
distortion caused by said curvature.
6. The apparatus of claim 5 wherein there are two said lenses and a
source of light directed through both of said lenses.
7. The apparatus of claim 6 wherein said two lenses are on opposite
sides of said cuvette, and have their axes substantially in
alignment, and a third lens having its axis at substantially a
right angle to the other axes.
8. A method of carrying out chemical testing comprising introducing
a fluid sample to be tested into a chamber, said sample being in
contact with a first porous barrier and a second porous barrier,
permitting at least some constituents of said sample to pass
through said first barrier and contact a first fluid reagent, at
least some of said constituents passing through said second barrier
to contact a second fluid reagent whereby the light transmission
characteristics of at least one of said reagents are altered.
9. The method according to claim 8 wherein said first reagent and
said second reagent are the same.
10. The method according to claim 8 wherein said first reagent and
said second reagent are different.
11. An apparatus adapted for chemical analysis comprising a cuvette
having therein a first porous barrier which serves to
compartmentalize said cuvette, and a first test reagent fluid in a
first reagent compartment in the cuvette, said barrier being in
direct contact therewith, said apparatus having means to provide an
electromotive force across said cuvette in the axial direction
towards said barrier, whereby said first reagent is driven across
said first barrier.
12. An apparatus adapted for chemical analysis comprising a cuvette
having therein a first porous barrier which serves to
compartmentalize said cuvette, and a first test reagent fluid in a
first reagent compartment in the cuvette, said barrier being in
direct contact therewith, said cuvette comprising the barrel of a
hypodermic syringe having a needle point extending from one, the
test reagent being in the far compartment relative to the needle
point, the first reagent compartment being in the plunger of said
syringe.
13. The apparatus of claim 12 wherein there is provided a second
reagent compartment containing a second reagent, a second porous
barrier in contact with said second reagent compartment and said
reagent therein, a sample chamber in said syringe adjacent said
point, both said first barrier and said second barrier in contact
with said sample chamber and the sample contained therein.
14. The apparatus of claim 13 wherein said reagents are different,
whereby two different tests can be run simultaneously on said
sample.
15. The apparatus of claim 12 wherein there is provided a second
compartment in said plunger, said second compartment containing a
reference fluid.
16. The apparatus of claim 12 wherein said plunger is of reduced
cross-section adjacent the end of said plunger nearest said point,
said barrier being on the reduced cross-section of said plunger,
the plane of said barrier being parallel to the axis of said
plunger.
17. An apparatus adapted for chemical analysis comprising a cuvette
having therein a first porous barrier which serves to
compartmentalize said cuvette, and a first test reagent fluid in a
first reagent compartment in the cuvette, said barrier being in
direct contact therewith, said cuvette comprising the barrel of a
hypodermic syringe having a needle point extending from one end,
the test reagent being in the far compartment relative to the
needle point, there being a chamber in the plunger of said syringe,
said chamber containing a reference fluid.
Description
This invention relates to apparatus for performing chemical
analysis and in particular to small load operation biomedical test
needs.
Recent advances in biochemistry have engendered many biomedical
diagnostic tests useful to the practicing physician. Tremendous
numbers of biomedical tests are routinely carried out daily in
hospitals and in independent medical laboratories, some even in the
doctor's office. The very number of tests has created a demand for
automated test procedures and equipment, and a well-equipped
medical laboratory can routinely conduct tests by the thousands.
However, creation of automated test facilities does not constitute
a complete response to the ever-increasing usage of test
procedures. Instances will always arise wherein the automated
facilities of the biomedical laboratory are simply not available,
for example, off-hour emergencies and isolated geographical
areas.
Accordingly, a real and substantial need exists for small load
analytic systems capable of operation by relatively untrained
technicians. The object of this invention is to provide improved
small load analysis systems.
Basically the rationale of the present invention is that many of
the chemical reactions involved in biochemical tests can be carried
out in a multichambered cuvette. The desired components of the
sample can transport across a porous membrane from a sample chamber
into a second chamber of the cuvette, to there undergo a chemical
reaction indicative of that reactant. Thus, for example, the
available CO.sub.2 present in a sample of blood or another fluid
will diffuse from a sample chamber through a hydrophobic
semipermeable membrane (e.g., Teflon) into a chamber containing an
aqueous alkaline solution of a color reagent like phenolphthalein
and react therein with the solution, changing its color. A
colorimeter measurement taken of the color indicator solution will
serve to determine accurately the available CO.sub.2 present in the
sample. If the sample chamber contains an acid reagent in addition,
then the total CO.sub.2 content of the original sample will be
released to diffuse through the membrane and the colorimeter
reading will measure the total CO.sub.2 in the sample.
For further understanding of the invention, reference is now made
to the attached drawings wherein:
FIG. 1 diagrammatically illustrates the basic structure of the
multi-chamber cuvette;
FIG. 2 is an exploded perspective of one form of the barriers of
the invention;
FIG. 3 illustrates a modified form of multi-chambered cuvette;
FIG. 4 is a diagrammatic view of another embodiment of the
invention;
FIG. 5 is a modification of the device of FIG. 4;
FIG. 6 is a diagram of another embodiment of the invention with
membranes at right angles to each other;
FIG. 7 is a diagram of an embodiment of the invention using
electric potential to assist in carrying out the test;
FIG. 8 shows a diagrammatic cross-section of a modification of the
cuvette or barrel which eliminates or reduces distortion caused by
curved sides;
FIG. 8A is another way to eliminate or reduce curvature distortion
by the use of lenses;
FIG. 9 is a convenient way of maintaining the membranes at the
desired distance from each other;
FIG. 9A is a modification of the device of FIG. 9 wherein the
membranes are separated by a tube;
FIG. 10 is a diagram of the device of FIG. 9A mounted in a sled
ready for insertion into the cuvette or barrel; and
FIG. 11 is a diagram of a form of the invention capable of carrying
out two tests on the same sample at the same time.
Referring now to the drawings, it may be seen that the basic
structure of the present invention involves a vial or cuvette 10
separated into at least two (three being illustrated) chambers or
compartments 12, 14 16 fixed in place by barrier spacers 18 and 20.
In the basic form of the invention shown in FIG. 1, cuvette 10 is
sealed at its open end by a cap 22. Chambers 14 and 16 are filled
by appropriate test fluids. Although in the form illustrated in
FIG. 1 chamber 12 is empty of test reagent, inclusion of a test
reagent in chamber 12 is also contemplated. For purposes of the
analysis, chamber 12 is charged with test sample, e.g., by
aperturing cap 22 with a hypodermic needle and forcing the sample
in through the needle.
An important aspect of the present invention is that all the
analytic tests contemplated for the present cuvette structure
involve passage of one component derived from the test sample
through a porous barrier. Normally the barrier is a semipermeable
membrane, but for some tests the pore size of the barrier may be
larger. Accordingly, the carrier can best be described as porous,
including within the meaning of the term, microporous membranes and
semi-porous membranes. The barrier may be hydrophilic or
hydrophobic in nature. The exact character of the membrane is
predetermined by the analytic test for which the cuvette is
constructed. However, all of the analytic tests for which the
present cuvette structure is adapted require that the barrier
prevent migration of all interfering component or components. To
repeat, the tests involve transport of some desired component or
constituent from the test sample across the barrier 18 into the
test fluid in chamber 14. In those tests where the analytic
procedure requires a second reaction, an additional barrier 20 and
chamber 16 are provided. In such instances, the reaction in chamber
14 creates or liberates a component which transports from the fluid
in chamber 14 through the barrier 20 into chamber 16.
The cuvette structure of the present invention normally is employed
with an optical read-out instrument which, depending on the
analytic test, may be a colorimeter, a fluorometer, a nephelometer,
in short, any of the many optical systems already being employed to
measure chemical, biochemical or biomedical test results.
Therefore, cuvette 10 is sized to fit into whatever standard
optical measurement device is appropriate to the particular test
for which the cuvette has been constructed. Appropriate optical
measuring equipment is widely available commercially, and virtually
every analytical test where optical measurement of the test results
is made has been calibrated to standard optical equipment, e.g.,
colorimeter, nephelometer, fluorometer, etc. Actually, many of the
recent advances in automated analysis have involved a change in
analysis technique or chemistry so that the test results can be
meaured by optical means.
A principal object of the present invention is to provide a manual
one-at-a-time or low-load counterpart to widely used automated
analysis systems. Practice of this invention contemplates making
the test results (automated or manual) strictly comparable. Repeat
tests or later tests analyzed in the automated laboratory can be
compared directly to the results of the manual test carried out in
the cuvette structure of the present invention.
Since many of the analytical test procedures to which the apparatus
of the present invention is adapted require liquid phase to liquid
phase transport of one component through a porous membrane, the
porous barrier layer structures and filling procedures should
minimize creation of air bubbles so that the barrier maintains
liquid on both surfaces thereof. To insure such complete contact,
practice of the present invention according to one preferred mode
thereof involves floating the barrier. The barriers 18, 20 may be
made free to move inside cuvette 10. Their exact position within
cuvette 10 is determined entirely by the volume of fluid in the
chambers 14 and 16 bound by barriers 18, 20. Thus, barrier 20
floats, so to speak, on the test fluid inside chamber 16; barrier
18 floats on the test fluid inside chamber 14. Needles to say, the
dimensions of cuvette 10 must be uniform and accurate, so that free
barriers 18 and 20 can slide the length of cuvette 10 and still
seal against fluid leakage from chamber to chamber.
In some cases, a small air bubble may deliberately be introduced
into chambers containing the liquid reagents so as to act as a
means of mechanical mixing; e.g., by rotating or vibrating the
device. Mixing would favor reaction rates and reduce back diffusion
of reaction products, thus shortening the time required for the
test. In other cases, reaction rates are so fast that no mixing is
necessary.
Illustrated in FIG. 2 is a preferred form of barrier, wherein
porous membrane 30, which may be a microporous membrane or a
semipermeable membrane which is hydrophilic or hydrophobic,
depending on the analysis involved, is a circular piece sandwiched
peripherally between centrally apertured members, hoop 32 and 34.
These three members are fused, glued or otherwise secured to form a
unitary barrier structure. The hoop portions 32, 34 of the barrier
constitute a continuous foot having significant bearing area
contacting the inside wall of cuvette 10. This ensures that the
barrier has sufficient structural rigidity to prevent buckling and
makes certain that the porous barriers 18 and 20 remain across
cuvette 10 and freely rest on the underlying test liquid. For
assembly purposes, circular membrane 30 and hoops 32, 34 are
preferably made of thermoplastic materials. They may be heat joined
readily; the hoops may be directly molded on around the peripheral
edge of porous membrane 30 which may be bonded chemically to one of
the hoops. For filling the cuvette mode illustrated in the
drawings, an air vent or aperture (not shown) may be provided
through hoops 32, 34.
A satisfactory way of providing the device depicted in FIG. 1 is to
start with a cuvette having a venting hole at the bottom. Barrier
20 is then introduced, and advanced a set distance down the tube,
the reagent for chamber 14 being layered over it so that when the
proper amount is reached, its meniscus forms a convex surface at
the lip of the tube. Barrier 18 is then deposited on this liquid
surface and pushed some distance down the tube, pushing barrier 20
and reagent 14 further down in the process. The device is then
inverted, the proper reagent for chamber 16 is delivered atop
barrier 20 through the vent hole, barrier 18 is pushed up to expel
residual air in chamber 16, and the vent hole is then sealed.
A modified form of cuvette is illustrated in FIG. 3. The cuvette
100 is part of a hypodermic syringe arrangement, being the barrel
of a standard hypodermic syringe with the usual plunger 102
structure closely fitted thereto. A restraining yoke 104 on the
rear of barrel 100 serves to limit rearward movement of plunger 102
and assures that a predetermined volume of sample fluid is taken up
through the needle 106. A protective cap 108 may be used to
surround and shield needle 106 and keep it bacteriologically
sterile, if desired.
A procedure, similar to that relating to the device of FIG. 1, can
be followed for filling the modified form of the device shown in
FIG. 3, except that the needle acts as a venting hole to allow
filling the reagents and barriers from above, and that barrier 112
is then advanced until fully seated near the needle, thus reducing
the prospective sample chamber volume to nearly zero.
In the construction illustrated by FIG. 3, two spaced-apart
floating porous barriers 110, 112 are provided. For many, and
perhaps most, biomedical tests only one such barrier is required.
In the illustrated mode, one test reagent is in barrel chamber 114
between barriers 110 and 112, and a second test reagent is in
barrel chamber 116 between plunger 102 and barrier 110. The volume
118 between 112 and the needle 106 may be air filled, evacuated, or
filled with a dliuent such as saline solution.
For conducting a test, the protective cap 108 is removed, and a
predetermined quantity of sample, e.g., expired air or blood, is
drawn through needle 106 into sample region 118 by rearward
movement of plunger 102 to the limited end of its rearward travel.
As plunger 102 is drawn back, the porous barriers 110 and 112 and
the test reagents in chambers 114 and 116 are drawn rearwardly (by
the suction), enlarging chamber 118 as the sample is drawn into it.
Thereafter, a component from the sample or test reagent traverses
porous barrier 112; for example, in a total CO.sub.2 test, H+ ion
crosses barrier 112 from the sample chamber, then CO.sub.2 diffuses
across barrier 112 entering chamber 114, crosses chamber 114,
traverses porous barrier 110 and enters the test reagent inside
chamber 116 altering an optical characteristic of the reagent.
After a given time interval, the cuvette is inserted into an
optical instrument, the optical path being, for example, along line
X--X through barrel 100 which normally is transparent glass or
plastic, and through the test solution in chamber 116.
In a particular embodiment of the invention, the reaction takes
place on or within the membrane itself. Normally, such a membrane
would be transparent or at least translucent in order to make the
test results readily visible. The results can be either in the form
of a color change, or a change in the opacity of the membrane. In
the latter case in particular, measurement of the results can be
advantageously carried out by the use of a device having the
affected membrane placed perpendicularly across the light path as
shown in FIG. 6.
It is also within the scope of this invention to use a syringe
having a hollow plunger. The hollow in the plunger can then act as
a chamber to hold a reagent, in which case the leading face of the
plunger consists of an appropriate barrier, or it can contain a
standard solution to be used as a comparison for the color change
resulting from the test reaction, in which case the end is sealed.
In FIG. 4, hollow plunger 36 fits inside syringe barrel 11 with
membrane 35 across its mouth. Sample chamber 37 is provided and the
reaction takes place in substantially the same way as in the device
of FIG. 3, except that the hollow plunger 36 forms one of the
chambers.
In FIG. 5, sample chamber 37 and reagent chamber 38 are separated
by barrier 35. Standard chamber 39 is provided in hollow plunger 36
to hold a reference solution to assist in comparing the results of
the test with a desired standard.
FIG. 6 shows a device having a hollow plunger 36 carrying membrane
44 with its plane axially aligned. Another membrane 43 is placed as
in the device of FIG. 5. A light source 51 and a photoelectric cell
52 are so positioned as to permit a beam of light to pass through
membrane 44 and impinge on cell 52. Any change in opacity of
membrane 44 can easily be read.
This form of the device is particularly suitable for use with
samples which are not clear, such as blood. Membrane 43 prevents
the passage of the occluding components of the sample (e.g., blood
cells) so that reagent chamber 38 contains only clear material
which will not interfere with the effect of the test reaction on
the light beam and photoelectric cell 52.
This embodiment is also useful inn those situations in which a
reaction product is precipitated on or within the barrier, that is,
in which the desired sample component passes through barrier 43,
diffuses freely through a carrier fluid or reagent in chamber 38,
and then reacts on the surface of a within the body of barrier 44
to produce a color deposit or a change in the membrane lucency. In
some cases, indicator particles may adsorb on the barrier
surface.
The plunger 36 of this embodiment can, of course, be used in
accordance with the devices of FIGS. 3, 4 and 5 as well as in the
manner heretofore described.
In yet modification of this invention as shown in FIG. 7, an
electromotive force is impressed across syringe 10 and plunger 41
by means of conductor 40 connected to a source of current 42. This
can be alternating or direct current, or a variant thereof, to help
drive the reagent and/or sample in the desired direction.
In certain types of visual or photometric measurement, the
distortion caused by curvature of the cuvette or barrel is
undesirable. This can be minimized or eliminated by the devices
shown in FIGS. 8 and 8A. In FIG. 8, a barrel 11 is shown which has
four flat portions 49. Light source 51 is directed through portions
49 to give an undistorted view of the results of the test. This is
particularly useful in nephelometry, since the Tyndall effect can
be observed readily by viewing at a right angle to the light beam.
Of course it is not necessary to have flats all around, since it is
not always necessary to view in all directions. Only those portions
through which it is intended to view need be flat.
This same problem can be solved by the device of FIG. 8A. Here, in
order to minimize the distortion (or lens effect) caused by the
curved cuvette or barrel, compensating lenses 50 are formed in or
attached to the cuvette or barrel 11 in the viewing area.
In those forms of the invention in which a double membrane is
desirable, the embodiment of FIG. 9 will prove useful. Membranes 43
and 44 are held in the desired relationship to each other by spacer
rods 45. This has the advantage of fixing the distance between the
barriers and preventing them from jamming or leaking.
A variation of this form is shown in FIG. 9A. Instead of a
plurality of spacer rods, hollow tube 47 extends from barrier 43 to
barrier 44.
In FIG. 10, there is shown a device using the tube structure of
FIG. 9A. Sled 46 surrounds tube 47 and is intended to fit within
the barrel of cuvette. Portions 53 seal against the inner wall of
the cuvette or barrel substantially preventing passage of fluid
except selectively through barriers 43 and 44 of tube 47.
A still further modification of the invention is shown in FIG. 11.
Barriers 43 and 44 may be the same or different. Similarly, reagent
chambers 38 and 38a may contain the same or different reagents.
Sample chamber 37 is common to both reagent chambers. This form of
the invention permits the running of two tests simultaneously in
the same apparatus using a single sample. It can also be used to
incorporate a standard for comparison to the test result. In the
latter case, no barrier is present on one side of the plunger and
the standard is sealed in.
As can be seen from the foregoing description, the present
invention is useful for conducting one test at a time. The
structure has the advantages of being light-weight, portable,
self-contained, and is well suited for use directly in a
physician's office, at bedside, even in an ambulance or in other
emergency situations. The test device can be employed in hospitals
during off hours, when the automated laboratory equipment is down
and laboratory personnel are unavailable. Few special skills are
needed to conduct the tests and unskilled nursing or paramedical
personnel, regulatory agency personnel (for food inspection,
environmental control, police, etc.) can conduct the analyses
accurately. In some instances, the ultimate reaction product is
stable enough so that the test may be stored, e.g., for legal
purposes.
Although the test procedures and reagents form no part of the
present invention, the widespread applicability of the
multi-chamber cuvette described above is noteworthy. The following
tests can be carried out therewith:
BUN Uric Acid Alcohol (blood/ Bilirubin Glucose expired air)
Albumin Carbon Dioxide Transaminase Ammonia Carbon Monoxide Alk.
phosphatase Antigen-antibody reactions
Many of the analytic tests, such as for example, the available
CO.sub.2 test, require only a single barrier cuvette.
Other tests require the two barrier assemblies as illustrated in
the drawing. One such test is the determination of uric acid. For
this test, the first barrier should be hydrophilic, and may, for
example, be a cellophane dialysis membrane. After the blood sample
has been drawn into the sample chamber, uric acid present in the
blood will diffuse through the cellophane dialysis membrane into
the first reaction chamber, and there react with uricase (present
in the preloaded reagent) to produce CO.sub.2. The CO.sub.2 will
diffuse back through the cellophane membrane into the sample
compartment, as well as forward into the second reaction chamber.
The second barrier should be a hydrophobic semipermeable membrane,
being for example, a fluorocarbon dialysis membrane (Teflon). The
second chamber test solution is an aqueous alkaline indicator so
that the CO.sub.2 crossing the hydrophobic semipermeable barrier
will react to cause a color change in the indicator solution. Since
the CO.sub.2 product is related to the original concentration of
uric acid in the blood sample, an optical color reading of the
indicator solution will constitute a measurement of the uric acid
concentration in the blood sample.
Another particularly useful test uses hemoglobin as the test
reagent. This can be either in liquid form (e.g., as a solution) or
in solid form (e.g., microcrystals). This material is particularly
useful in testing for carbon monoxide in the presence of various
air pollutants such as carbon dioxide, sulfur dioxide, and nitrogen
oxides. The following description will be specifically directed to
testing for the presence of carbon monoxide, but the principles
are, of course, applicable to other similarly reacting materials as
well.
Hemoglobin reacts with oxygen to form a compound which is a
brownish color. Carbon monoxide also reacts with hemoglobin to form
a slightly different material which has a cherry red color.
Obviously, the color change can be observed visually or
colorimetrically and compared with a reference standard if
desired.
As an additional variation, a color filter can be placed between a
source of radiation (e.g., light) and the test solution. The
wavelengths which the filter will pass should be those which
correspond with the absorption peaks of the carbon monoxide--
hemoglobin derivative. These are to be found at 535 and 570.9
millimicrons. Alternatively, a source of mono-chromatic light can
be used, again corresponding with these absorption peaks. A
radiation-sensitive cell such as a photocell is placed in the path
of the beam from the source so that the light impinges on it after
passing through the test chamber. Thus, the changes brought on by
the test will result in variations in the amount and type of
transmitted light. The photocell can easily and automatically read
these. This method will enhance the sensitivity of the test and
permit more accurate readings.
A still further improvement on this method and device consists of
splitting the radiation into two beams and passing each beam
through a separate filter before the beams pass through the
reaction chamber. One filter is of the same character described in
the preceding paragraph and permits the absorption peak wavelength
to pass. The other permits only "neutral" wavelengths to pass, that
is, wavelengths such that both the oxygen derivative and the carbon
monoxide derivative of hemoglobin absorb equally. There is provided
a radiation-sensitive cell (in this case a photocell) for each of
the beams, and the difference between the two readings is compared.
By using this method, the device will automatically correct for
variations in source intensity or with changes in airborne
particles which might reduce transmission independently of the test
reaction (e.g., smoke, fog, etc.).
Of course, these methods can be connected up to an alarm or other
warning device which will trip when the concentration of the
undesired pollutant reaches a predetermined level. Similarly, a
relay could be used to close or open doors or windows or to turn on
ventillating fans and the like.
Many of the pollutants found in air are deleterious because they
have undesired reactions with hemoglobin. Some of these reactions
are irreversible and result in permanet damage while others like
the carbon monoxide specifically referred to can be reversed if
caught in time. For this reason, the use of hemoglobin as a test
reagent for various types of pollutants in air is generally
suitable. In fact, analogs of the theme moiety of hemoglobins such
as polypyridine derivatives are also satisfactory for this
purpose.
While only a limited number of embodiments of the inventin have
been specifically disclosed, such variations as would be apparent
to one having reasonable skill in the art can be made without
departing from the scope or spirit thereof. The invention is to be
broadly construed and not to be limited except by the character of
the claims appended hereto.
It is obvious to anyone having ordinary skill that these methods
can be used with gases as well as with liquids where the nature of
the test so permits.
* * * * *