JPH0213261B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical quantitative method for a liquid sample in which a color-forming compound in the liquid sample is optically analyzed.

Conventionally, trace amounts of harmful substances such as phosphorus compounds in seawater or river water have been targeted as target components, and spectrophotometric methods and solvent extraction methods have been applied to detect and quantify the target components in liquid samples. A method is proposed.

The former spectrophotometric method involves adding an appropriate coloring reagent to a liquid sample, allowing it to react with the quantitative target component in the liquid sample, and placing the colored liquid containing the generated coloring compound in an absorption cell to determine the coloring of the liquid. This method measures the intensity of light, specifically absorbance. However, this method has the disadvantage that when the concentration of the component to be quantified in the liquid sample is extremely low, the absorbance of the colored liquid is low and quantification is not possible. In such cases, measures are taken to improve sensitivity by changing the optical path length of the absorption cell for absorbance measurement from the usual 10 mm to 20 mm or 50 mm, but this operation also increases sensitivity. It is only 2 to 5 times as large.

In addition, in the latter method, a colored compound in the aqueous phase is extracted into an organic solvent using an organic solvent in an amount of one-fifth or one-tenth of the volume of the aqueous phase. This is a method in which the coloring intensity of the organic solvent phase is increased to 5 or 10 times the intensity of the aqueous phase and then measured. However, the improvement in sensitivity achieved by this method is only about 5 to 10 times at most, and depending on the type and properties of the color-forming compound, it may not be extracted into the organic solvent or may be insufficiently extracted. It may not be possible to apply it effectively.

In this way, when the concentration of the target component to be quantified in a liquid sample is low, conventional spectrophotometric methods can achieve dramatic increases in sensitivity, even if methods such as the use of an absorption cell with a long optical path length or the application of a solvent extraction method are used. This is considered to be the limit of the spectrophotometric method.

The present invention aims to eliminate the limitations of such conventional methods and provide an optical quantitative method for liquid samples that can measure the target component in a liquid sample with high sensitivity and precision even if it is in a trace amount. Its characteristics are that a coloring reagent is added to a liquid sample containing a color-forming compound to form a colored liquid sample that does not contain precipitates, and the colored liquid sample is filtered using a filter medium. , coloring the filter medium in a state in which the color-forming compound colored by the coloring reagent concentrates on the filter medium, and irradiating the colored filter medium with light to emit reflected light from the colored filter medium or the colored filter medium. The method is to determine the concentration of the color-forming compound in the liquid sample by measuring the intensity of transmitted light.

The present invention can be called a so-called colored material colorimetric method because it uses a material as described above and measures the intensity of irradiated light on the colored part of the material, and has a corresponding mechanism. The invention will be specifically explained based on FIG.

In FIG. 1, a liquid sample is sent to a reaction tank 3 and collected by a liquid sample collection pump 2 which is driven for a certain period of time by the operation of a timer 1. Further, a certain amount of coloring reagent is added to this reaction tank 3 from reagent tanks 6 and 7 by another pump 4 and 5 which is also activated by the timer 1, and at the same time, a stirrer 8 attached to the reaction tank 3 is added. Stirring is carried out for a certain period of time. During this time, the coloring compound contained in the liquid sample reacts with the coloring reagent, and the liquid sample becomes colored as a whole, becoming a colored liquid.

Next, this coloring liquid is sent to an automatic filtration mechanism by operating a valve 9 which is opened and closed in response to a command from a timer 1, and the coloring compound is filtrated therein. The automatic filtration mechanism basically consists of a filtration device 10 and a pair of liquid supply devices 11 and 11' for supplying colored liquid to the filtration device 10. These pair of liquid supply devices 11, 11' are provided with corrosion-resistant rubber rings 12 fitted to their opposing tips.
It may be a real pipe, and is configured such that the filter device 10 is sandwiched between them. Further, the liquid supply devices 11, 11' are connected to the moving device 1.
3, the device 10 can be moved up and down, back and forth, or rotated, etc.
It has become possible to move away from it.

The filtering device 10 may also be made of a suitable material 14 such as paper.
1, and is configured to be movable in the left-right direction in FIG. 1 by means of a moving device 13.

Therefore, the colored liquid sent by opening and closing the valve 9 passes through the liquid supply device 11 and is sent to the filter section 14, and the suction pump 15 is operated according to the command from the timer 1 to perform suction, and the filter material is is colored.
After the passing, the liquid supply devices 11 and 11' are separated vertically, and the passing device 10 is moved to the optical detection device 16 side. That is, in FIG.
Move to the position where the light source 17 is placed on the colored part of the material.
A certain amount of light is irradiated from the sensor, the coloring intensity of the reflected light is measured, and a signal is displayed on the display device 18 and outputted to the printer 19. These operations are also performed according to instructions from timer 1, and furthermore,
In the example shown in FIG. 1, while the coloring intensity is being measured in this way, a new test for the colored liquid is being carried out in the pass section 14'' which has moved to the position of the pass section 14, and these Operations are performed continuously.

In this way, in the present invention, if the filter device 10 is provided with a plurality of filter sections 14, 14', 14'', the same kind of liquid sample in the reaction tank 3 can be sampled by the relative movement with the liquid supply devices 11, 11'. It is possible to continuously and repeatedly measure the
If a plurality of corresponding liquid supply devices 11, 11' are provided, continuous measurement of different types of liquid samples is also possible.

In the practice of the present invention, the production of the colored liquid may be the same as in conventional spectrophotometric methods.
However, in the present invention, like the conventional spectrophotometric method and solvent extraction method, the target is the case where the color-forming compound in the liquid sample is colored by the addition of a coloring reagent, and the target is not the case where the color forming compound forms a precipitate. do not. Coloring reagents are appropriately selected depending on the type of coloring compound, and are exemplified in Examples. Also,
The liquid sample may be seawater, river water, and is not specified in the present invention. Filter paper and membrane filters are suitable as filter media. In addition, to measure the intensity of light from a colored part, it is possible to measure the intensity of light reflected from the colored part as shown in Figure 1, but it is also possible to measure the intensity of light transmitted through the colored part. good.

According to the present invention, even when the concentration of the component to be quantified in a liquid sample is extremely low and the absorbance of the colored liquid is too low to be measured by normal spectrophotometry, the colored liquid is passed through an appropriate material, so it can be used as a coloring reagent. The filter media becomes strongly colored due to the colored compounds in the liquid sample. For example, even if the coloring of a colored liquid is extremely small and appears colorless and transparent to the human eye, if the liquid is passed through a piece of wood, clear coloring can be seen on the piece of wood. The degree of coloring of this strongly colored material can be measured by irradiating light from a light source and measuring the intensity of the reflected light from the colored area, or by irradiating light from a light source onto the colored area and measuring the intensity of the light that has passed through that area. Measure the quality. Therefore, even if it contains trace amounts of colored compounds that cannot be measured by conventional spectrophotometry, quantitative measurement is possible, and it also has high sensitivity and
High accuracy.

The reason why the sensitivity of the present invention is dramatically improved can be considered as follows. That is, in the conventional method,
Since the colored liquid itself, which is colored by the color-forming compound, is measured, when the degree of coloring is small, the lowest measurable concentration of the target compound is usually
Limited to around 1ppm.

However, in the present invention, the filter medium is colored by the coloring compound passed through a suitable material such as paper or membrane filter with a diameter of about 45 mm, so that the coloring compound dispersed throughout the liquid sample is colored. Color compounds are concentrated on a small area of the material surface. Therefore, the coloring on the material becomes dramatically stronger and this intensity is measured, so the lowest measurable concentration of the target component for quantitative determination is 1/1000th of 1ppm, that is, 1ppb or even lower. It can be. The reason why the material is colored by the colored compound is that the colored compound in the liquid sample, which does not contain precipitates and in which the colored compound is dissolved, is adsorbed to the filter medium. Conceivable.

In addition, the present invention is extremely simple in operation because it simply involves filtering a colored liquid sample, coloring the filter medium, and optically quantifying the colored filter medium.

In this way, the present invention can be applied not only to heteropolyacid-forming reactions, but also to strongly colored dye-forming reactions, metal chelate-forming reactions, and all other colored compound-forming reactions in colored liquids, such as those described in the Examples below. It can be used to measure colored compounds.

Example 1 A phosphoric acid standard solution prepared from potassium phosphate was added to artificial seawater prepared according to JIS K-250 to prepare artificial seawater containing phosphorus compounds. Pour 200 ml of this artificial seawater into a 250 ml volumetric flask and prepare a coloring reagent solution (ammonium molybutate 15
100ml of a solution of g dissolved in 500ml of distilled water, concentrated sulfuric acid
140ml dissolved in 900ml distilled water, 250ml, 27g
of ascorbic acid dissolved in 500ml of distilled water.
100ml, 0.34g of antimonyl potassium tartrate 250ml
(mixed with 50ml of solution dissolved in ml of distilled water) 25
ml was added and stirred to produce a colored compound of phosphorus, and the total volume was diluted to 250 ml to obtain a colored liquid.

Next, this colored liquid was passed through a membrane filter with a diameter of 45 mm (pore size: 0.3 μm), and the intensity of the coloring on the membrane filter was measured using a reflected light method. The results are shown in FIG. When coloring using the reflected light method, the full scale is usually 100 graduations, so
As shown in Figure 2, when the phosphorus compound concentration is 2.0 μg/250 ml, approximately 12 scales of the measured reflection intensity can be sufficiently measured, and the lowest quantifiable phosphorus compound concentration is approximately 1 scale of reflection intensity. 0.1μg/250ml
(0.4ppb).

For comparison, the absorbance of the above colored solution was measured by spectrophotometry using an absorption cell with an optical path length of 10 mm, and the relationship between the concentration of the phosphorus compound in the volumetric flask and the absorbance was plotted to create a calibration curve. Created. The results are shown in FIG. 3, where the absorbance of the colored liquid is only 0.007 when the phosphorus compound concentration is 20 μg/250 ml. However, normal spectrophotometric methods usually measure absorbance in the range of 0.1 to 0.6, so an absorbance of 0.007 cannot be used for very accurate analysis.

In other words, in the absorption photometry method according to the Marine Observation Guidelines Act,
Although it is impossible to quantify the phosphorus compound concentration at 2.0 μg/250 ml, it is understood that according to the present invention, it is possible to measure the concentration sufficiently at 0.2 μg/250 ml, and even at 0.1 μg/250 ml.

Example 2 200 ml of artificial seawater containing a phosphorus compound prepared in the same manner as in Example 1 was placed in a 250 ml volumetric flask, and ammonium molybutate solution (15 g of ammonium molybutate) was added in accordance with JIS K-0120 method.
Dissolve 150 ml of distilled water, add 180 ml of concentrated sulfuric acid and 800 ml of water to make a total volume of 1), and add 25 ml of stannous chloride (1 g of stannous chloride).
(dissolved in 5 ml of hydrochloric acid, diluted to 50 ml with distilled water, added a small piece of metal tin) and stirred to form a colored phosphorus compound, bringing the total volume to 250 ml.
It was diluted to make a colored liquid.

When the same procedure as in Example 1 was carried out using this colored liquid, the results shown in FIG. 4 were obtained. In this example, for a phosphorus compound concentration of 2.0 μg/250 ml, the measured value of reflection intensity is on 19 scales, which is fully quantifiable according to the present invention.

I did this for comparison. According to the same spectrophotometric method shown as a comparison in Example 1, the calibration curve was as shown in Figure 5, and the absorbance was small, so
It is difficult to quantify phosphorus compounds at 2.0 μg/250 ml using the JIS K-0102 method.

Example 3 800 ml of artificial seawater containing a phosphorus compound prepared in the same manner as in Example 1 was placed in a 1000 ml volumetric flask and measured in the same manner as in Example 1, and the results shown in Figure 6 were obtained. . From this result, the measured value of reflection intensity for a phosphorus compound concentration of 2.0 μg/1000 ml is sufficient to measure 2 ppb in 19 scales, and 0.1 ppb of phosphorus concentration corresponding to 1 scale of reflection intensity.
It can be seen that it is also possible to measure

On the other hand, when measured using the JIS K-0102 method, 2.0ppb
The absorbance of the liquid was so small that it could not be measured.

Example 4 The present invention was carried out in exactly the same manner as in Example 2. However, in this example, a transmitted light method was used in which the colored material was irradiated with light and the intensity of the light transmitted through the colored part was measured. The results are shown in FIG.

Here, the measured value in the case of a phosphorus compound concentration of 2.0μg/250ml is at the full scale of 1000,
It was on a 600 scale. That is, in this case, the sensitivity was even higher than in Example 2 using the reflected light method.

Example 5 According to Example 2, tin compounds were determined by the phenylfluorone method, and the results shown in FIG. 8 were obtained.

Note that FIG. 9 shows the results obtained using the JIS K-D102 absorption photometry method, and it can be seen that the method of the present invention achieves a dramatic improvement in sensitivity even in this case.

[Brief explanation of drawings]

Figure 1 is a system diagram illustrating the device of the present invention and explaining its operation, Figure 2 is a diagram showing the relationship between phosphorus compound concentration and reflection intensity scale, and Figure 3 is a diagram showing the relationship between phosphorus compound concentration and absorbance. Figure 4 is a diagram showing the relationship between phosphorus compounds and the reflection intensity scale, Figure 5 is a diagram showing the relationship between phosphorus compound concentration and absorbance, and Figure 6 is a diagram showing the relationship between phosphorus compound concentration and absorbance. Figure 7 is a diagram showing the relationship between compound concentration and reflection intensity scale, Figure 7 is a diagram showing the relationship between phosphorus compound concentration and transmission intensity scale, and Figure 8 is a diagram showing the relationship between tin compound concentration and reflection intensity scale. Figure 9 shows the relationship between tin compound concentration and absorbance, respectively. 3... Reaction tank, 9... Valve, 10... Passage device, 11,
11'...Liquid supply device, 13...Movement device, 14,1
4', 14''... section, 16... light intensity detection device, 18
...Display device.

Claims (1)

[Claims] 1. Adding a coloring reagent to a liquid sample containing a color-forming compound to form a colored liquid sample free of precipitates, filtering the colored liquid sample using a filter medium,
Coloring the filter medium in a state in which the color-forming compound colored by the color-forming reagent is concentrated on the filter medium,
The method is characterized in that the colored filter material is irradiated with light and the intensity of the reflected light from the colored filter material or the transmitted light of the colored filter material is measured to determine the concentration of the coloring compound in the liquid sample. Optical quantitative method for liquid samples.