JP2000283956A - Substance detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably detect a specified substance in solutions to be inspected by adding the specified substance in common to the solutions before measuring a plurality of solutions using a molecular film so that various characteristics non-related to presence/absence of the specified substance are substantially uniform. SOLUTION: In detecting a harmful substance in solutions to be inspected such as river water and a waste water from a plant, a conductivity increasing substance and a pH adjustment substance of appropriate quantity are added to each solution for pre-processing, and the conductivity and the pH value of each solution are thus substantially constant. To achieve the measurement by a probe having the molecular film, the information attributable to the variance of the conductivity and the pH value is canceled from the measurement value, and the measurement value dependent on the harmful substance can be extracted selectively. The harmful substance can be detected without any load in the operation. The conductivity and the pH value of the reference solution for measurement are not necessarily made to coincide with those of the solution to be inspected so long as the difference in electric potential can be grasped for each solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for stably detecting specific substances such as harmful substances contained in river water, industrial wastewater, purified water, circulating water, beverages, and the like.

[0002]

2. Description of the Related Art There are various methods for detecting a specific substance, for example, a harmful substance, contained in river water or industrial wastewater, including a chemical analysis method. Japanese Patent Laid-Open No. 10-267878 discloses a method for detecting cyanide ions using a molecular film of an amphipathic substance or a bitter substance as a sensor instead of the conventional method.

In this method, a model formula is determined on the basis of a value obtained by measuring a standard solution having a known cyanide ion concentration, and a value obtained when the test solution is measured is determined by the model formula. To measure the cyanide ion concentration of the test liquid.

[0004]

However, in the above-mentioned measuring method, signal processing becomes complicated when a plurality of test liquids having different sampling conditions are compared and measured.

For example, a plurality of test liquids collected from different rivers and different factory wastewaters have greatly different pH and conductivity. In addition, even when collected from the same river or factory, if the collection times are different, the pH or conductivity may change significantly.

For this reason, it is necessary to measure not only a standard solution having a changed cyanide concentration but also a solution having a changed pH and a changed conductivity so as to determine a model formula. The burden of is large. In addition, a plurality of molecular films having different response characteristics to changes in not only the concentration of cyanide but also pH and conductivity are required.

An object of the present invention is to solve the above problem and to provide a substance detection method capable of stably detecting a specific substance in a plurality of test liquids having different sampling conditions and manufacturing conditions.

[0008]

According to a first aspect of the present invention, there is provided a method for detecting a substance, comprising the steps of: converting a specific substance in a plurality of test liquids having different sampling conditions or production conditions into an amphipathic substance; Or a substance detection method for detecting using a molecular film composed of a bitter substance, before measuring the plurality of test liquids with the molecular film, adding a predetermined substance to the plurality of test liquids in common. In addition, the predetermined characteristics of the plurality of liquids to be tested, which are irrelevant to the presence or absence of the specific substance, are made substantially uniform.

According to a second aspect of the present invention, there is provided the substance detection method according to the first aspect, wherein the predetermined substance is a conductivity increasing substance, and the predetermined characteristic is conductivity. I do.

According to a third aspect of the present invention, in the method for detecting a substance according to the first aspect, the predetermined substance is an alkaline substance or an acidic substance, and the predetermined characteristic is pH. I do.

According to a fourth aspect of the present invention, there is provided the method for detecting a substance according to the first aspect, wherein the predetermined substance is an alcohol substance, and the predetermined characteristic is an alcohol content.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an inspection device 20 that inspects for the presence of harmful substances (cyan, environmental hormones, heavy metals, oils, etc.) such as river water, industrial wastewater, and beverages using the method of the present application.

In FIG. 1, an inspection apparatus 20 includes a container 21 for containing a reference liquid and a plurality of liquids to be inspected, a probe 22, and a voltage detector 3 for detecting a potential difference between the probe 22.
5, an A / D converter 36 that converts the output of the voltage detector 35 into a digital value, an arithmetic unit 37 that performs arithmetic and comparison processing on the output of the A / D converter 36, and a determination result of the arithmetic unit 37. Is notified by a notifying device 38 for notifying.

The probe 22 is immersed in a liquid contained in a container 21 and has a reference electrode 23 for outputting a reference potential for measurement, and a molecular film 25 of an amphipathic substance or a bitter substance. are doing.

The surface of the reference electrode 23 is made of potassium chloride 100 mmol / l so as not to react with lipids in the liquid.
Is covered with a buffer layer 24 fixed with agar, and a lead wire 22a is connected thereto.

The molecular film 25 is made of a base material 2 made of acrylic or the like.
6 is fixed in a state where one side is exposed,
An electrode 28 is provided on the opposite surface of the molecular film 25 via a buffer layer 27 equivalent to the buffer layer 24 of the reference electrode 23, and a lead wire 22b is connected to the electrode 28.

The molecular film 25 is formed by an amphiphilic substance or a bitter substance having a non-polar hydrophobic part and a polar and hydrophilic part, with the hydrophilic part facing the surface. The schematic structure is shown in FIG.

In FIG. 2, each molecule 31 is composed of a spherical hydrophilic group 31a and a hydrocarbon chain 31b whose atomic arrangement extends long from the hydrophilic group 31a. The matrix 33 on the surface of the membrane member 32 (comprising a polymer and a plasticizer described later)
(A surface structure, a microstructure having a two-dimensional spread) is partially accommodated in a form (for example, a molecule 31 ′) dissolved in the matrix.

The molecules of the molecular film 25 include negatively charged lipid molecules such as dioctyl phosphate (2C ₈ POOH), oleic acid, diphenyl phosphate, decyl alcohol, etc., trioctylmethyl ammonium chloride (TOMA), n Positively charged lipid molecules such as octadecyl chloride, bipolar lipid molecules such as lecithin, or bitter substances such as brucine, caffeine, quinine, strychnine, nicotine cocaine, and isohumulone. Among them, those having high responsiveness to the specific substance to be detected (in this case, harmful substance) are selectively used.

The molecular film 25 is prepared by mixing the above-mentioned lipid molecules, bitter substances, base polymer and plasticizer at a predetermined ratio. For example, polyvinyl chloride (PVC) is used as the polymer, and dioctyl phthalate (DOP), dioctylphenylphosphonate (DOPP) or tricresyl phosphate (T
800 mg mixed with the above lipid molecules and bitter substances using CP) is dissolved in 10 cc of THF, transferred to a flat-bottomed container (for example, a petri dish of 85 mmφ), and placed on a uniform heated plate at about 30 ° C. Then, for 2 hours, the THF is volatilized to obtain a molecular film having a thickness of about 200 μm.

When the probe 22 is immersed in a liquid, the distance between the reference electrode 23 and the molecular film 25 is made constant so that the measurement conditions do not change. May be supported at regular intervals.

The leads 22 a and 22 b of the probe 22 having the molecular film 25 are connected to a voltage detector 35.

The voltage detector 35 is constituted by, for example, a differential amplifier, detects the difference (voltage) between the potential of the reference electrode 23 and the potential of the molecular film 25, and outputs the difference to the A / D converter 36.

The A / D converter 36 converts the output voltage of the voltage detector 35 into a digital value and outputs the digital value to the arithmetic unit 37.

The arithmetic unit 37 is constituted by a microcomputer, and stores an output value of the A / D converter 36 in a memory 37a when receiving a storage instruction M from an operation unit or the like (not shown). The arithmetic processing and the comparison / determination processing are performed on the stored value of.

The output device 38 is constituted by a display device, a printer, or a communication device for communicating with other devices, etc., and displays and prints the judgment result of the arithmetic device 37 and notifies other devices by a signal.

Next, a description will be given of a case where the inspection apparatus 20 is used to inspect, for example, free cyanide in river water.

First, a method of acquiring data relating the concentration of free cyan and the output voltage of the probe 22 before inspecting unknown river water will be described with reference to the flowchart of FIG.

In order to determine this relationship, river water to be inspected is used. Generally, river water has low conductivity and varies depending on sampling conditions.
It varies between slightly alkaline.

For this reason, as a pretreatment, river water that does not contain free cyan among river water collected from a river is used as a standard solution, and a predetermined amount (for example, 5 liters) of a standard solution is added with a salt ( A predetermined amount (for example, 10 mM) of KCl, NaCl, KBr, etc.) is added (S1). The addition of this salt results in a relatively high conductivity of the standard solution.

Subsequently, an alkaline substance (KOH, NaO) is added as a pH adjusting substance to the standard solution to which the conductivity increasing substance is added.
H, LiOH, etc.) or acidic substances (HCl, H ₂ SO
₄ , HNO ₃ etc.) is added in a predetermined amount (for example, 10 mM) (S2).

By adding this pH adjusting substance, the pH value of the standard solution becomes relatively strongly alkaline or acidic.

When the harmful substance to be detected is free cyanide, an alkaline substance is used as a pH adjusting substance, and the pH of the standard solution is made slightly alkaline to about 12, so that free cyanide added later is stabilized. Can be changed.

As described above, the standard solution to which the conductivity-increasing substance and the pH-adjusting substance are added is divided into appropriate amounts (for example, 500 ml), and free cyanide is added to each standard solution at a different concentration (for example, 0 to 10 ppm). Then, the first to Mth concentration reference liquids are prepared (S3).

Subsequently, a measurement reference liquid serving as a measurement reference is prepared. This measurement reference liquid is mixed with water containing no harmful substance to be detected (the water may be river water previously collected from the river from which the liquid to be tested was collected) and the conductivity increasing substance and p.
An H adjusting substance is added to make the conductivity and the pH value almost equal to those of each concentration reference solution (S4).

After the first to Mth concentration reference liquids and the measurement reference liquid are prepared in this way, the probe 22 is immersed in the measurement reference liquid, and the voltage Vr (n) is stored in the memory 37a. To store the voltage V (m) when the probe 22 is immersed in the m-th concentration reference solution, and calculate the voltage difference Vs (m) = V (m) -Vr (m) by the arithmetic unit 37. , For all concentration reference liquids, starting from the lowest cyan concentration (S5 to S10).

In this measurement, since the conductivity and the pH value of each concentration reference solution and the measurement reference solution are substantially equal, the conductivity and p
No voltage difference due to variation in the H value occurs, and only the voltage difference depending on the concentration of free cyan can be extracted.

Therefore, the relationship between the concentration of free cyan and the voltage difference can be grasped from the voltage differences Vs (1) to Vs (M) obtained by this measurement and the concentration of each concentration reference solution ( S11).

Here, when obtaining the concentration of free cyan in the liquid to be tested, the data (relational expression) indicating the above-mentioned relationship is stored in the memory 37a in advance. To simply determine whether or not the concentration of free cyan in the liquid to be tested is higher than a specified value, the potential difference corresponding to the specified value is stored in the memory 37a as a threshold.

When the relational expression and the threshold value are stored in the memory 37a, the voltage difference Vs (1) to Vs (1)
By outputting Vs (M) and setting the relational expression and the threshold value determined by the inspector from this value in the memory 37a or by giving a calculation command to the calculation device 37, the calculation device 3
7 may obtain a relational expression or a threshold value and store it in the memory 37a.

Next, a case where the inspection apparatus 20 is used to check the presence or absence of harmful substances in a plurality of N test liquids collected from a river under different collection conditions (collection time and collection place) will be described with reference to the flowchart of FIG. Will be explained.

As a pretreatment for measurement, the same amount (for example, 10 mM) of the conductivity-increasing substance is added to a predetermined amount (500 ml) of each test object liquid as described above (S2).
1). By the addition of the conductivity increasing substance, the conductivity of each test liquid is made substantially uniform at a relatively high value.

Here, the output voltage of each river water when KCl (potassium chloride) was added as a conductivity increasing substance for six river waters (river water not containing cyan) which actually differ in sampling conditions. FIG. 5 shows the results of measuring the variation.

As apparent from FIG. 5, when KCl is not added, the output voltage has a variation (difference between the maximum value and the minimum value) of 1.4 mV, and the KCl is slightly (10 mV).
mM), the variation sharply decreases to 0.2 mV or less.

When actually measured using the molecular film 25,
Since the output dependent on free cyan is about several mV, it can be seen that if the output due to the deviation of the conductivity falls within 0.2 mV or less, only the output dependent on free cyan can be extracted almost accurately.

Next, the same pH adjusting substance (in this case, an alkaline substance) is added in the same amount (for example, 10 mM) to each of the test liquids to which the conductivity increasing substance is added (S2).
2).

By adding this pH adjusting substance, the pH value of each test object is made uniform with relatively strong alkalinity.

Next, a measurement reference solution is prepared. The measurement reference solution may be used as it is or may be newly prepared (S23).

With these pretreatments, the probe 22 is immersed in the measurement reference liquid and the voltage Vr (n) is increased while the conductivity and the pH of the first to n-th test liquids and the measurement reference liquid are almost equal. The voltage V (n) when the probe 22 is immersed in the n-th test liquid is stored in the memory 37a, and the voltage difference Vs (n) = V
The process of calculating (n) -Vr (n) is performed for all the test liquids (S24 to S29).

Also in this measurement, since the conductivity and the pH value of each of the test solution and the measurement reference solution are almost equal, no voltage difference due to the variation in the conductivity and the pH value occurs, and the voltage depends on the concentration of free cyanide. Only the voltage difference can be extracted.

The measurement conditions are the same as when the relationship between the concentration of free cyan and the voltage difference was determined.

Therefore, based on the voltage differences Vs (1) to Vs (N) obtained in this measurement and the relational expressions or threshold values stored in the memory 37a, the free cyan of each liquid to be inspected is determined. Can be detected, or it can be determined whether the density is equal to or higher than the specified density (S30).

As described above, in this embodiment,
When detecting harmful substances using river water or factory effluent as test liquids, an appropriate amount of a conductivity increasing substance and a pH adjusting substance are added to each test liquid as pretreatment, and the conductivity and pH of each test liquid are added. Since the measurement is made with the probe 22 having the molecular film 25 after making the values substantially uniform, the information due to the variation in the conductivity and the pH value can be canceled from the measurement values, and the measurement depending on the harmful substance can be performed. The value can be selectively extracted, and harmful substances can be detected stably without putting a burden on arithmetic processing.

In the above description, the conductivity and the pH value of the measurement reference liquid are adjusted to the test liquid. However, if the difference in potential between each test liquid can be grasped, the measurement reference liquid is not necessarily the same as the test liquid. It is not necessary that they have the same conductivity and pH value.

Although the method of detecting a harmful substance after adding a conductivity-increasing substance or a pH-adjusting substance to a liquid to be inspected such as river water has been described above, the method of inspecting another liquid to be inspected is not described. The additive may be changed according to the difference in the sampling conditions of the test target liquid or the difference in the manufacturing conditions.

An example is shown in Table 1 below.

[Table 1]

Table 1 shows characteristics to which the molecular film 25 may respond and which has no relation to the response of the harmful substance to be detected.

To explain an example of Table 1, for example, when alcoholic beverages having different production conditions (brands) are detected as liquids to be tested and their harmful substances are detected, a substance having an increased alcohol content such as ethanol is used as a pretreatment for each liquid to be tested. When the probe 22 measures the alcohol content of each test solution after adding an appropriate amount to the test solution, the measured value does not include information due to the variation in alcohol content, and the harmful substance can be stably detected. .

When harmful substances are detected using juices having different production conditions (brands) as test liquids, a sweet taste increasing substance such as saccharose is added as a pretreatment to each test liquid in an appropriate amount. If the degree of sweetness is made substantially uniform and then measured with the probe 22, the harmful substance can be stably detected without the information resulting from the variation in the degree of sweetness being included in the measured value.

Similarly, when soups and the like having different manufacturing conditions (brands) are used as test liquids to detect harmful substances, as a pretreatment, an appropriate amount of a taste increasing substance such as MSG or IMP is added to each test liquid. If the degree of sweetness of each test solution is made substantially uniform and then measured with the probe 22, the harmful substance can be stably detected without including information due to the variation in the degree of umami in the measured value.

Although the case where the specific substance to be detected is a harmful substance such as cyan has been described above, the detection target is not limited to the harmful substance, and other components may be used as long as the concentration does not change with the substance to be added. Substances can also be detected. For example, when an alcohol substance in juices is detected as a specific substance, a sweet substance is used as an additive substance, and a lipid or a bitter substance having high responsiveness to the alcohol substance is used as the molecular film 25.

[0062]

As described above, according to the substance inspection method of the present invention, a specific substance in a plurality of liquids to be inspected having different sampling conditions or production conditions is determined by using a molecular film comprising an amphipathic substance or a bitter substance. In the method of detecting a substance to be detected, a predetermined substance is added in common to a plurality of test liquids before measuring the plurality of test liquids with a molecular film, and the predetermined liquid irrespective of the presence or absence of the specific substance in the plurality of test liquids The characteristics are almost uniform.

For this reason, the information resulting from the variation in the predetermined characteristic can be canceled from the measured values, and only the measured values depending on the specific substance can be extracted. Can be detected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an inspection apparatus used in the present invention.

FIG. 2 is a diagram showing a schematic structure of a molecular film;

FIG. 3 is a flowchart showing a substance inspection procedure according to the embodiment;

FIG. 4 is a flowchart illustrating a substance inspection procedure according to the embodiment;

FIG. 5 is a graph showing a change in the variation of the output voltage with the addition amount of KCl.

[Explanation of symbols]

 Reference Signs List 20 inspection apparatus 22 probe 22a, 22b lead wire 23 reference electrode 24 buffer layer 25 molecular film 26 base material 27 buffer layer 28 electrode 29 support material 31 molecule 31a hydrophilic group 31b hydrophobic chain 35 voltage detector 36 A / D converter 37 operation Device 37a Memory 38 Output device

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[Procedure amendment]

[Submission date] May 12, 1999 (1999.5.1
2)

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Continued on the front page (72) Inventor Norihiro Maeda Anritsu Co., Ltd. 5-27-10 Minami-Azabu, Minato-ku, Tokyo (72) Inventor Yuji Sato 5-1-27 Minami-Azabu, Minato-ku, Tokyo Anritsu Corporation F term (reference) 2G046 AA31 AA34 DC16 DC17 DC18 EB09 FA01 FA04 FA05 FA07

Claims (4)

[Claims] 1. A substance detection method for detecting a specific substance in a plurality of test liquids having different sampling conditions or manufacturing conditions using a molecular film made of an amphipathic substance or a bitter substance, Before measuring the liquid with the molecular film, a predetermined substance is commonly added to the plurality of test liquids so that predetermined characteristics of the plurality of test liquids irrespective of the presence or absence of the specific substance are made substantially uniform. The substance detection method characterized by the above-mentioned. 2. The method according to claim 1, wherein the predetermined substance is a conductivity increasing substance,
2. The method according to claim 1, wherein the predetermined characteristic is conductivity.
The substance detection method as described. 3. The method according to claim 1, wherein the predetermined substance is an alkaline substance or an acidic substance, and the predetermined characteristic is pH. 4. The method according to claim 1, wherein the predetermined substance is an alcohol substance,
The substance detection method according to claim 1, wherein the predetermined characteristic is alcohol content.