JPS60105944A - Electrophotometric method and apparatus using capillary tube with total reflection long optical path - Google Patents

Abstract

PURPOSE:To achieve a higher sensitivity by a method wherein a capillary tube absorption cell is arranged to house a solvent with a larger refractive index than material thereof and a sample dissolved or dispersed therein and light is made incident at one end of the cell to be absorbed. CONSTITUTION:A capillary tube 5 as absorption cell is so arranged to introduce a solvent with a larger refractive index than material thereof at the inlet 6 and drain from the outlet 7 and an incident light Io from a light source 1 is made to enter the incident end of the tube 5 through a lens 2 or the like. Then, the emission light I from the emission end of the tube 5 is detected with a photodiode 8 and recorded on a recorder 11 via an amplifier 9 while done on a CRT12 or the like via a microprocessor 10. Thus, the tube 5 can be lengthened with a limited space by bending while attenuation due to reflection on the wall of the tube 5 can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to spectrophotometric methods and apparatus, and more particularly to spectrophotometric methods and apparatus using total internal reflection long-path capillaries.

BACKGROUND OF THE INVENTION Spectrophotometric methods are well known, in which visible light, infrared rays, or ultraviolet rays are passed through a solution of a substance to be measured contained in an absorption cell to quantify the substance. The sensitivity in spectrophotometry increases as the optical path length increases, making it possible to detect substances at low concentrations. In other words, the optical path length and the detectable substance concentration limit are inversely proportional. However, increasing the optical path length increases the size of the analyzer, so conventionally only disk-shaped or cylindrical cells have been used.

For example, a typical conventional colorimeter (spectrophotometer that uses visible light) uses an absorption cell in which a solution is housed in a disk-shaped or cylindrical cell with a diameter of about 2 mm and a length of about 1 to 10 α.
Light is transmitted in the direction of its axis. An absorption cell with such a short optical path length cannot achieve sufficient sensitivity.

Attempts by the Inventor Generally, two kinds of absorption cells are manufactured from a light-transmitting inorganic material such as glass or quartz, and water, acetone, carbon tetrachloride, lower alcohol, etc. are used as a solvent for the substance to be measured. The inventor fabricated a capillary tube with a length of about 1 m using glass (Pyrex glass) as the material of the absorption cell, and measured the light transmittance using the above-mentioned solvent such as water as the solvent. It was confirmed that high sensitivity of the photometric method could be achieved.However, 1
Since a capillary tube with a length of more than m requires a large space if it remains straight, it is virtually impossible to industrially manufacture a spectrophotometer. Therefore, the present inventor attempted to configure the above-mentioned capillary tube as a loop tube, but almost no light was emitted from the other end of the capillary tube even though a powerful laser beam was used as a light source. When we investigated the cause, we found that the capillary wall is a specular reflection type, so the light is attenuated as it is repeatedly reflected on the capillary wall.

Therefore, the present inventor came up with the idea of replacing the capillary tube constituting the absorption cell with a total reflection type material, and was able to arrive at the present invention. An object of the present invention is to provide a highly sensitive spectrophotometric method and apparatus using an absorption cell having a long optical path and little attenuation of infrared and ultraviolet light.

Summary of the Invention The method of the present invention includes storing a sample dispersed or dissolved in a solvent having a refractive index greater than that of the sting in a capillary absorption cell, and absorbing light by entering light from one end of the absorption cell. The apparatus of the present invention is a spectrophotometer using a total reflection long-path capillary tube.

The conditions for total reflection on the inner wall of the capillary are defined by Snell's law. Now, when the angle of incidence of light on the end face of the capillary is θ, the refractive index of the material of the capillary wall is n, and the refractive index of the solvent accommodated in the back side of the capillary is nl, the total reflection condition is sin θ
<647); n1, and the relationship n□)nl, that is,
It is important that the refractive index of the solvent is greater than that of the capillary. Such a condition cannot be achieved by conventional combinations of tubes made of glass or lime with solvents such as water, and it is necessary to use a solvent with a high refractive index such as carbon disulfide instead of water. be.

According to the present invention, a significant increase in sensitivity is achieved compared to conventional spectrophotometric methods. In the capillary tube used, not only the optical path length is effectively increased due to reflection from the tube wall, but also
Since the total internal reflection condition can be satisfied even in a spirally wound form, it is possible to design a very long optical path length, and the sensitivity can be improved by 3 to 4 orders of magnitude compared to the conventional one in a narrow space. Additionally, since it is a capillary tube, there is an advantage that fewer samples and solvents are required.

The material of the capillary tube is determined by the relationship with the refractive index of the solvent. When a high refractive index solvent such as benzene, acetophenone, carbon disulfide, or 1-promonataline is used as the solvent, Pyrex glass, quartz, plastic materials, etc. can be used. When water is used as a solvent, a plastic material or the like known to have a refractive index smaller than that of water can be used. It is not necessary that the entire capillary tube has a refractive index lower than that of the solvent; it is sufficient that at least the inner wall portion of the tube has a lower refractive index. Therefore, for example, a capillary tube made of glass whose surface is coated with a low refractive index can be used, and in the following examples, an example in which the surface is coated with a resin is given.

Further, in the following embodiments, an example will be described in which light with a single wavelength is input, but it is also possible to directly input light having a continuous spectrum (for example, a tungsten lamp) into the capillary tube.

In this case, if the capillary tube is sufficiently long, light of different wavelengths will pass through it, so it is possible to achieve so-called time resolution in which the emitted light is emitted in order according to the wavelength, and a spectrometer is not required.

An example of an apparatus for carrying out the method of the present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram of the spectrophotometer of the present invention, FIG. 2 shows a total reflection long optical path capillary in another embodiment, and FIG. 6 is used in the embodiments of FIGS. 1 and 2. FIG. 3 is a cross-sectional view showing an example of a light incident part and a solvent inflow part.

Referring to FIG. 1, light from a suitable light source such as a laser, a tungsten lamp, or a xenon lamp 1 is passed through a lens 2, a filter 3.4, etc. through a capillary tube 5, which is an absorption cell.
input to the input end of the

The capillary tube 5 is made of, for example, Pyrex glass (refractive index 1474).
) and other materials. The smaller the inner diameter of the capillary tube, the better, but it can be determined as appropriate by taking into account the amount of sample and solvent, flow resistance, and pump capacity. For example, a capillary tube with an inner diameter of several centimeters requires a specific sample if the optical path length is increased, but if a capillary tube with an inner diameter of several hundred μm is used, a large optical path length can be achieved even with a small amount. A solvent having a refractive index higher than the refractive index of the material is introduced into the capillary tube 5 from an inlet 6 (if used as an anti-type, it is used as is; if used as a solvent, a solution in which a sample of the substance to be measured is dispersed or dissolved) is introduced from an inlet 6,
It is discharged to the output lower. Note that an appropriate pump (not shown) is used for the liquid transfer.The solvent may be any solvent as long as it has a refractive index greater than the refractive index of the capillary tube and is suitable as a sample solvent. For example, for Pyrex glass, solvents such as benzene, acetophenone, carbon disulfide, and 1-monaphthalene can be used. The light emitted from the output end of the capillary tube 5 is detected by a photodetector 6 such as a photodiode, passes through an amplifier 7, and is recorded on a recorder 11, or is subjected to predetermined processing by a microbe stomach processor 10 and sent to a negative SS tube 12 or a graphic printer. 13 etc.

FIG. 2 shows an example of a helical capillary tube 14 used in place of the straight capillary tube 5 in FIG. In this example the solvent is inlet 15
and is discharged to the outlet 16. With the capillary tube 14, very long tube lengths can be achieved even with limited space, and correspondingly very long optical path lengths. - As an example, a pipe length of 50 m can be easily designed. Fig. 3 shows a more specific example of the purchase of the entrance end of the capillary tube 5 or 14 and the solvent inlet. The T-tube 19 uses a graphite backing 20.21 to support the quartz rod 18 and the aligned end of the open-ended capillary tube 5 (or 14). Further, a solvent inlet pipe (stainless steel or the like) 6 (or 15) is connected using a stainless steel backing 22.

It will be clear to those skilled in the art that the shape of the capillary tube is not limited to a helical shape, but can have any curved shape.

The following examples illustrate spectrophotometry with visible light;
It will be clear to those skilled in the art that ultraviolet or infrared light may also be used as a light source.

Example 1 Examples of the spectrophotometric method of the present invention, including comparative examples, will be described below.

Light transmission was measured using a straight capillary tube and a capillary tube wound in one loop. The capillary tube was made from Pyrex glass with a refractive index of t474. The straight one is 1m long, IN-
The length of the pool-shaped one was α7m. As a solvent, water (refractive index 133), acetone (i, 35), ethanol, F
l/(1,36), n-butyl alcohol/I/(159
), acetylacetone (t45), carbon tetrachloride (1,
45), benzene (1,49), acetophenone (t
s 5 ), carbon disulfide (162), and 1-bromonaphthalene (1,65)). The incident light used was a wavelength of 750 nm from a tungsten lamp. As a result, it was found that the light transmittance in a straight capillary is about twice as high when using a solvent with a refractive index larger than t474 than when using a solvent with a refractive index smaller than 1474. In the case of a 1-loop tube, the transmittance of a solvent with a refractive index of 1474 or less is 6.
However, with solvents of 1474 or higher, almost no attenuation occurred on the inner wall surface of the tube due to the extra length. It was found that the transmittance and the Gf were the same for solvents with a refractive index greater than 1474, regardless of the type of solvent.

As mentioned above, the total reflection long optical path capillary is superior to the specular reflection type, and especially when it has a curved part, it must be of the total reflection type. The absorbance of phosphorus (7 male, 7 omolypdate, hete ν polyp, 50 pgP/d) was measured in various organic solvents with different refractive indexes.Water, acetone, and n-butyl alcohol were used as solvents with a refractive index of 1415 or less. By changing the mixing ratio of carbon disulfide and acetone as the above solvent,
A mixed solvent having a refractive index of 4+S to 162 was used. Inner diameter approximately 2mm, length approximately (L7m Pyrex glass!I!I
! ? The absorbance measured at a light wavelength of 750 nm using an AI-pu capillary is about 200 times that of a conventional 1 m cell for solvents with a refractive index of 146 or less, and about 400 times for solvents with a refractive index greater than 1474. Ta.

Example 3 Using a spiral capillary tube made of Pyrex glass with an inner diameter of 2 mm and a length of 4 tn, the same absorption sensitivity as in the previous example was measured using an acetone-carbon disulfide solvent with a refractive index greater than t474.

Approximately 10,000 times the sensitivity was obtained compared to the cell number 1. Furthermore, similar measurements were performed on various capillary tubes, and the results shown in Table 1 were obtained. All values are approximate values.

Table 1 Conventional cell C1ctL) 1 Total reflection flooded capillary 1) Straight type length α5ηt 2XiO" α7m 1.5XiO-' 1ffl lX1O' 2) Curved type length 1+n, lX10' 3) 1-Pipe type length 0 .7ff+15×IO-” 4) Helical length 4 ml×10′ Example 4 Iodine was measured by colorimetry using a carbon tetrachloride-carbon disulfide mixed solvent (with a refractive index greater than 1474). As a result, 5 x 10'M of iodine could be detected in a 1m straight line.

Example 5 Mercury was detected by the dithizone method, which is a typical spectrophotometric method. Compared to a conventional 1-cylinder cell, a 1 m linear absorption tube has a 200 to 400 times more power, and a 4 m total internal reflection spiral capillary tube has a 10
A high sensitivity of 00 to 2000 times or more was obtained.

Example 6 Measurements similar to those in Example 3 were performed using a xenon lamp, He-Ne laser light, and carbon disulfide solvent.

The Pyrex glass capillary tube used was a spiral tube with a length of 10 m. The sensitivity is about 2000 times that of a conventional 1α cell for laser light, and about 40 times more sensitive for light from a xenon lamp.
It was 00 times. This is probably due to the difference in optical transmission format between non-parallel light and parallel light, resulting in a difference in optical path length.

￥Male side 7 Light (75 Dnm) from a xenon lamp was passed through carbon disulfide-phosphorus molybdenum blue housed in various total reflection capillary tubes of various lengths, and the absorbance was measured. Table 2 shows the concentration of phosphorus that gives 1% absorption and the sensitivity improvement (based on the conventional 1α cell).

Table 2 Total reflection type capillary cell 1, straight type length 0.5 m 20 53. XiO″I 017r
n 15 4.7×10t# 1rn 10 7X10
” 2 Spiral type (Pyrex) Length 4m 2.5 2.8X10” # 10ffl 1.0 7XiO” 3, Spiral type (Silicone coated Pyrex) Length 2
5m a4 1.75X10'IF 51] FI Q,
2 5.5X10' Note: 1.2 capillary has an inner diameter of 1 to 21
The hair H1 tube of 1M, 3 has an inner diameter α2■, and Q, i ~ 1t
A flow hook of ttl/min (honf pressure 101rI1./cm' or less) was used.

As described above, according to the present invention, compared to conventional cells,
A four-digit improvement in sensitivity can be seen. Furthermore, by using a capillary tube with a curved portion, the optical path length can be increased while saving the space occupied by the light absorption cell, so that a compact and highly sensitive spectrophotometer and spectrophotometer can be realized.

It will be apparent to those skilled in the art that many variations are possible within the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the spectrophotometer of the present invention, FIG. 2 is a diagram showing an example of a spiral capillary tube, and FIG. 3 is a cross-sectional view showing an example of the light incident end and solvent inlet of the capillary tube. be. The main parts in the figure are as follows. 1: Light source 2.3.4: Optical system 5: Capillary tube 6; Solvent inlet a: Solvent outlet 8: Photodiode 14: Spiral soft hair IWI tube 15: Solvent inlet 16: Solvent outlet ■o2 Incident light X: Outgoing light procedure Amendment document January 12, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office Indication of the case 1982 Patent Application No. 212566 Title of the invention Spectrophotometry using a total internal reflection long optical path capillary and the subject of the amendment by the person who makes the device correction Contents of amendment The description is amended as shown in the attached sheet as follows. 1. In the 5th line of page 5, the word ``ash'' is corrected to ``English''. 2. In the third line from the bottom of the same page, correct "Primonataline" and "Bromonaphthalene". 3. In the 7th row of the 6th even, [can be done, and in the following example, an example is given in which a cap is worn. ” can be 1. ” he corrected. 4. On the 9th line of the same page, correct the word ``ahead'' to ``light.''0 5. On the 814th line of the same page, the word ``to pass through,'' is followed by ``
"By injecting light intermittently in a pulsed manner."

Claims (4)

[Claims] (1) A capillary absorption cell contains a solvent having a refractive index greater than that of the material of the absorption cell, and a sample dissolved or dispersed therein, and light is caused to enter the absorption cell from one end to cause light absorption. , a spectrophotometric method using a total internal reflection long-path capillary tube. (2) A light source, a total reflection capillary tube having an input end and an output end for the light from the light source, an inlet and an outlet for the solvent to the capillary tube and a sample entrained therein, and an outlet for the light from the output end. A spectrophotometer using a total internal reflection long path capillary tube, including a means for sensing. (3) The spectrophotometer according to item 2 above, wherein the capillary tube has a curved portion. (4) The spectrophotometer according to item 2 above, wherein the capillary tube is spirally wound.