JPH0815133A - Analytic element - Google Patents

Abstract

PURPOSE:To measure the infrared absorption spectrum of a liquid sample with high accuracy and sensitivity by applying a substrate, having a groove deposited on the surface thereof with a thin metal film, tightly to another substrate and then introducing a sample into the groove. CONSTITUTION:The analytic element 1 comprises a smooth substrate 2 and another substrate 5 having a groove 4 deposited, on the surface thereof, with a thin metal film 3. The substrate 2 is made of a material having refractive index higher than that of a sample or the atmosphere and transparent in the infrared region, e.g. Al2O3 or MgO. The substrate 5 is made of silicon and provided with a groove 4 of predetermined depth, a sample introduction port 6, and an air vent 7 by photolithography and etching. The substrates 2, 5 are tightened by means of a clip 8. A sample 9 is introduced through the sample introduction port 6 into the groove 4 through capillarity using a syringe 10, for example. The air is discharged from the groove to the outside through the air vent 7. Since the depth of groove is just equal to the length of optical path length in the sample, highly accurate analysis is realized using an optical path of short length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample cell for measuring an infrared absorption spectrum of a low viscosity liquid sample.

[0002]

2. Description of the Related Art A conventional transmission type liquid sample cell is described in "Material analysis by infrared method (Koichi Nishida, Reikichi Iwamoto,
(1986), Kodansha Scientific, pp. 69-71). Here, the sample is sandwiched between two window materials and the thickness is adjusted with a fixing screw, and the capillary film method is used, or the window material, spacers, and frame are fixed with an adhesive. Liquid cells are described.

Also, a general measuring apparatus of the attenuated total reflection method is
In the same book, “Material analysis by infrared method (from page 106
P. 07) ".

A high-sensitivity infrared absorption spectrum measuring method using a total reflection prism and a metal is discussed in "Applied Spectroscopy (1988) Vol. 42, pp. 1296 to 1302". Here, the prism-sample-metal thin film Otto
The measurements are made in a configuration of placement. Using a germanium prism, a polyvinyl acetate thin film as a sample is formed on the prism, and silver is vapor-deposited thereon to a thickness of 20 nm for measurement. As a result, 5 times the SN of the conventional
It is possible to measure the ratio.

An example of highly sensitive measurement of a molecule in an aqueous solution is described in "Surface Science (1985), Vol. 158, Vol. 61.
Pp. 6 to 623 ". Here, high-sensitivity detection of mercaptobenzothiazole (MBT) dissolved in an acidic aqueous solution is performed using a total reflection prism on which silver is vapor-deposited, and measurement is performed in a Kretschmann arrangement of prism-metal-sample. MBT C
= S The peak of stretching vibration disappears and instead Ag (I) MBT
It is suggested that the local electric field that causes the increase in infrared absorption in the Kretschmann configuration extends only to the distance of the molecular layer adsorbed on the evaporated silver. .

[0006]

The infrared absorption spectrum measured by the transmission method of a liquid, especially an aqueous solution, is difficult to control the thickness of the sample, and the optical path length is not constant, so that the reproducibility of the measurement is poor and the quantitative analysis is performed. Could not be used for. Also, maintenance such as cell cleaning and assembly was complicated. In addition, the conventional high-sensitivity infrared absorption spectrum measurement method using a metal thin film and a total reflection prism is mainly for solid samples, and an example of measurement for an aqueous solution is
Limited to Kretschmann placement.

The cause of the increase in infrared absorption in the measurement of the Kretschmann configuration using this aqueous solution as a sample is an increase in the surface electric field due to localized plasmons excited by the light incident on the metal fine particles constituting the metal thin film. It is estimated from the experimental results that the increased distance of the surface electric field is about several nm. Therefore, it is necessary to increase the infrared absorption that the molecules in the aqueous solution have a chemical interaction with the metal and the adsorption layer of the molecule to be measured exists near the metal thin film where a local electric field is generated. Analysis of stable molecules was not possible.

On the other hand, in the case of the Otto arrangement, non-radiative surface plasmon resonance, which is excited when light is incident on the metal film at a certain angle, is considered to be the cause of the increase in infrared absorption.
As mentioned above, there is no measurement example in an aqueous solution. In the Otto arrangement, it is necessary to allow light to enter the metal thin film from the prism side through the sample layer, but since the light seeps from the prism to the sample side is only a few μm, the liquid can be made into such a thin prism. It was difficult to install on top. Therefore, the conventional infrared spectrum measurement method using a combination of a metal and a prism cannot perform highly sensitive measurement of an aqueous solution.

[0009]

In order to solve the above problems, a groove is formed by photolithography and etching, a substrate having a metal thin film formed on the groove surface is brought into close contact with another substrate, and a sample is introduced. The sample was introduced into the groove by providing the opening of, and the thickness of the sample was controlled by the depth of the groove. In addition, a metal thin film was formed on the groove surface in order to measure the infrared absorption spectrum with high sensitivity.

[0010]

The above means operates as follows. The thickness of the sample held on the first substrate is set to the thickness of the groove of the second substrate by bringing the second substrate in which the groove is formed into close contact with the first substrate and forming a cell configuration in which the groove of the second substrate is filled with the sample. It can be defined by depth. Further, by using etching for forming the groove, the depth of the groove can be controlled on the order of μm, and the thickness of the sample can be specified to be extremely thin. In the infrared absorption spectrum measurement by the transmission method, the depth of the groove becomes the optical path length in the sample as it is, and by measuring with an extremely short optical path length, the analysis of molecules dissolved in a solvent with large infrared absorption such as water Can be performed accurately.

Further, in the high-sensitivity infrared absorption spectrum measurement by the attenuated total reflection method using a metal thin film, the light bleeding from the optical waveguide substrate is formed by forming the sample layer extremely thin.
It reaches the surface of the metal thin film formed on the groove surface through the sample and excites surface plasmon resonance on the metal surface. The surface plasmon resonance on the metal surface increases the infrared absorption of the sample in contact with the metal, and the infrared spectrum can be measured with high sensitivity. Further, since this analytical element can be mass-produced in a semiconductor process or the like, it can be used as a disposable cell, and complicated maintenance such as cell cleaning is unnecessary.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing an analytical element of a first embodiment of the present invention. The analysis element 1 includes a smooth first substrate 2
And a second substrate 5 having a groove 4 on the surface of which a metal thin film 3 is formed by vapor deposition. The first substrate 2 is made of Al ₂ O ₃ , MgO, ZnSe, Si, G.
For example, a material having a refractive index larger than that of the sample or the atmosphere and transparent in the infrared region is used. The second substrate 5 is made of silicon, and has a predetermined depth (0.5 μm in this embodiment) of the sample setting groove 4 formed by photolithography and etching, and a sample inlet 6, which is a through hole 6, and a vent 7. Is formed. Since silicon etching is used for processing the sample mounting groove 4, it is possible to control the depth on the order of μm.
The first substrate 2 and the second substrate 5 are pressure bonded by the clip 8.

The sample 9 is a sample inlet 6 such as a syringe 10.
Is introduced into the groove 4 by capillary action. At that time, the air in the groove 4 is discharged to the outside of the groove through the air vent 7.

2 and 3 are cross-sectional views of analytical elements 11 and 12 using the aqueous solutions of the second and third embodiments of the present invention as samples. The analysis element 11 shown in FIG. 2 is formed on the surface of the bonding surface between the gold thin film 3 deposited on the second substrate 5 of the analysis element 1 shown in FIG. 1 and the sample introduction port 6 surface and the second substrate of the first substrate 2. The oxide film 13 is formed by ion sputtering. The surface of the substrate material such as silicon or zinc selenide is hydrophobic and easily repels water. Therefore, the surface of the sample introduction part is made hydrophilic by the oxide film and the sample installation groove 4
The sample can be rapidly developed therein.

The analytical element 12 shown in FIG. 3 is obtained by filling the grooves 4 of the analytical element 1 shown in FIG. 1 with fine particles 14 of a water-absorbing substance such as cellulose. The sample can be introduced into the groove 4.

FIG. 4 shows a form of measurement of an infrared absorption spectrum of an aqueous solution by a transmission method using the analytical element 1 shown in FIG. Holder 15 for analytical element 1 in the sample chamber of the infrared spectrometer
Thus, the sample layer 9 in the groove 4 is installed so as to be perpendicular to the infrared light 16. The depth of the groove 4 of this analysis element 1 is 0.5.
In μm, this depth is the thickness of the sample 9 as it is, that is,
It is the optical path length in the sample. Since this analysis element can be mass-produced in the semiconductor process, etc., it can be used as a disposable element that is inexpensive and has little error between elements, and measurement can be performed without the hassle of cleaning and sample exchange like the conventional transmission type sample cell. . Also, contamination of the sample is eliminated by making it disposable.

FIG. 5 shows a form of measurement of an infrared absorption spectrum of an aqueous solution by the attenuated total reflection method using the analytical element 1 shown in FIG. A high-sensitivity measurement with the analysis element 1 requires a sufficient amount of light to excite surface plasmon resonance that causes high sensitivity of infrared absorption. Therefore, a bright Fourier transform infrared spectrometer or infrared laser of an optical system is required. It is used in analyzers that use a light source. The analysis element 1 emits the infrared light 16 from the light source 17 into the incident substrate 18 for entering the first substrate 2 which serves as an optical waveguide and the infrared light propagating through the first substrate to the detector. It is installed in a holder 20 provided with a prism 19 for use. The holder 20 is installed in the sample chamber, and the analysis element is of a type that can be fitted into the holder. When exchanging samples, the analytical element 1 can be removed from the holder and the elements can be exchanged.

The infrared light 16 emitted from the light source 17 becomes p-polarized light through the polarizer 21 and is incident on the prism 18 near the critical angle of the prism. The infrared light is diffracted at the angle of the prism 18, enters the first substrate 2 of the analysis element 1 which is in contact with the prism 18, reaches the output prism 19 while undergoing multiple reflection in the substrate, and is transmitted to the detector by the prism 19. Emit. The light totally reflected at the interface between the first substrate 2 and the sample 9 is 2 to
It penetrates into the sample as evanescent wave about 3 μm.

The depth of the sample setting groove 4 of this analysis element is 0.5.
Since it is μm, an evanescent wave reaches the gold thin film 3 and surface plasmon resonance is excited. This surface plasmon resonance increases the infrared absorption in the sample, and the infrared absorption spectrum of the sample can be measured with high sensitivity.

FIG. 6 is an overall view of a blood glucose meter 22 using whole blood using the high-sensitivity analysis element 1 shown in FIG. 1 as a sample. A small stationary analyzer, an analytical element for dropping a sample, a keyboard 23 for inputting data relating to the sample, a printer 24 for outputting the blood glucose level measured by this device and the blood glucose level of the patient over time, and A display 25 is provided.

FIG. 7 is a block diagram of the blood glucose meter shown in FIG. The infrared light 27 emitted from the infrared light source 26 is the analysis element 1
Light of a specific wavelength is absorbed by the blood in the device and emitted to the interferometer 28. The light with the phase difference generated by the interferometer 28 is
The signal is guided to the detector 29, passes through the AD converter 30, and is input to the computer 32 as a digital signal 31.

The signal is converted into the absorbance for each wave number by Fourier transform. The relationship between the blood glucose level and the absorbance spectrum of the blood spectrum at 1181-950 cm ⁻¹ was calculated by multivariate analysis in advance using a calibration formula of 1181-950 of the sample.
The blood glucose level in the sample is calculated by including the absorbance series of cm ^-1 . The calculated blood glucose level is notified to the measurer by the output mechanism 33 such as a display or a printer.

FIG. 8 shows the correlation between glucose measured by the blood glucose meter of the present invention and the conventional enzymatic method. The result is γ = 0.96
2 was good. In the present invention, it is possible to perform the same measurement as the conventional enzyme method without using a reagent.

[0024]

According to the present invention, the infrared absorption spectrum of a liquid sample can be measured with high accuracy and high sensitivity.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an analysis element according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an analytical element according to a second embodiment of the present invention.

FIG. 3 is a sectional view of an analytical element according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view of a usage example of the analysis element of the present invention.

FIG. 5 is an explanatory diagram of a usage example of the analysis element of the present invention.

FIG. 6 is an explanatory diagram of a blood glucose meter using the analysis element of the present invention.

FIG. 7 is a block diagram of a blood glucose meter.

FIG. 8 is a graph showing the effect of the present invention.

[Explanation of symbols]

1 ... Analytical element, 2 ... First substrate, 3 ... Gold thin film, 4 ... Groove, 5
... Second substrate, 6 ... Sample introduction port, 7 ... Degassing port, 8 ... Clip, 9 ... Sample, 10 ... Syringe.

Claims (10)

[Claims] 1. An optical cell for measuring infrared absorption of a sample by an attenuated total reflection method or a transmission method, comprising: a first substrate;
The second substrate provided with a groove in which a metal thin film is formed on the surface of the first substrate is adhered, a sample is filled in the groove, and the thickness of the sample is determined by the depth of the groove filled with the sample. Analytical element characterized by controlling the height. 2. The analytical element according to claim 1, wherein the second substrate is formed by patterning the shape of the groove by photolithography and forming the groove by etching. 3. An analysis element comprising the second substrate according to claim 1 having a sample introduction port and a degassing port. 4. The metal thin film according to claim 1,
Analytical element consisting of silver, copper, aluminum and platinum. 5. The analytical element according to claim 1, wherein the surface of the sample contact portion of the first substrate and the second substrate is modified with a hydrophilic group such as a hydroxyl group or an amino group or an oxide film. 6. The analysis element according to claim 1, wherein the grooves formed in the second substrate are filled with water-absorbing fine particles such as polyethylene oxide and polyamide. 7. The device according to claim 1, wherein the first substrate has an infrared light incident mechanism into the first substrate and an infrared light emission mechanism from the first substrate to a detector. An analysis element whose emission mechanism is a diffraction grating or prism or an optical fiber. 8. The analysis element according to claim 1, wherein the second substrate is made of silicon. 9. The analytical element according to claim 1, wherein the first substrate is made of a crystal such as germanium, zinc selenide, or silicon which has a refractive index of 1.4 or more and is transparent in the infrared region. 10. An infrared spectrometer having a computer unit for processing an infrared light source, an interferometer, a detector, and a signal detected by the detector according to claim 1, wherein the analysis element is used as a sample cell. The blood analyzer used.