JPS63243860A - surfactant sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention provides a sensitive film at the detection end of the electrode body, and brings the sample into contact with the sensitive film to control the surfactant concentration in the sample. The present invention relates to a surfactant sensor for detecting a surfactant.

Conventional ■ and ■ In recent years, with the increase in detergent consumption, the contamination of environmental water by surfactants, especially ionic surfactants, has become a social problem, and it has therefore become important to accurately measure surfactants. ing. In this case, the method specified in JIS K 0101-1986 is known as a method for measuring ionic surfactants, but since this method requires complicated measurement operations, it is easy and quick to measure ionic surfactants. As a measuring device to achieve this purpose, a sensitive membrane is attached to the detection end of the electrode body containing the internal electrode and internal liquid, and the sample is brought into contact with this sensitive membrane. A surfactant sensor that measures the surfactant concentration in a sample has been proposed.

Conventionally, as the above-mentioned surfactant sensors, those shown in (1) and (2) below are known.

■ A sensor using a PVC membrane plasticized with N,N-dimethyloleamide or a nylon membrane plasticized with phenol as a sensitive membrane (T, Higuchi et al.
1. chem, 42, 1674.1970) The sensitive membrane of this sensor is a two-component system that does not contain an ion exchanger as a permeating proboscis.

■ A coach wire type sensor (Fujinaga et al.
1, Chem, ↓6.1842.1974) The sensitive membrane of this sensor is made by dissolving an ionic association of sodium alkylbenzenesulfonate and methyltricaprylammonium chloride in decanol, and using this to plasticize PVc. It is a three-component system containing the above-mentioned ionic association as a sensitive substance for anionic surfactants.

However, the sensor of
(7) On the other hand, there is no Nernst response in a wide range for anionic surfactants such as tetraphenylborate ions (Figure 8), It does not have satisfactory performance as a sensor.

In addition, the potential gradient of the sensor (■) is a relatively good value (57 m
V) is obtained, but the linear region is narrow <(10-' to 10-
3.M/II) also does not have satisfactory performance for measuring anionic surfactants. Also, this sensor cannot be used for cationic surfactants.

The present invention was made in view of the above circumstances, and has a Nernst response to both cationic surfactants and anionic surfactants over a wide range of concentrations, and has a fast response speed. The present invention aims to provide a surfactant sensor that can easily and quickly measure ionic surfactants such as anionic, anionic, and amphoteric surfactants.

5. To increase the fortune telling to 7° The inventors of the present invention have conducted intensive research to achieve the above objective, and as a result, they have developed polyvinyl chloride. - When a sensitive membrane is formed by plasticizing with nitrophenyl octyl ether and using this polyvinyl chloride, surprisingly, no sensitive substance is added (for both cationic surfactants and anionic surfactants). It was found that the present invention shows a good Nernst response (for example, a potential gradient of 58.6 mV and a linearity of 10-6 to 10-"M/j' for anionic surfactants) and a fast response speed. I came to do this.

In other words, the general method for making a surfactant sensor is to use an ionic association of an anionic surfactant and a cationic surfactant as an ion exchanger, as shown in item ① above, and then use it in an appropriate solvent. A method is used in which a membrane fixed with melted PVC is used as a sensitive membrane. In an electrode using such a sensitive membrane, the lifetime of the sensor is limited by the elution of the sensitive substance and solvent into the sample. Therefore, in order to improve the characteristics of the sensor, it is best to devise ways to minimize the outflow of the sensitive substance and solvent from the membrane. The inventors achieved improved sensor performance by simplifying the membrane composition. The idea of simplifying the membrane composition had already been considered in the method of T. Higuchi et al., but as mentioned above, there was no Nernst response to anionic surfactants. The present inventors used orthophenyloctyl ether (o-NPO) as a solvent.
It was found that when immobilized with PVC using E), Nernst response was good even to cationic and anionic surfactants.

Therefore, in the present invention, a sensitive membrane is provided at the detection end of an electrode body containing an internal electrode and an internal liquid, and the surfactant concentration in the sample is detected by bringing the sample into contact with this sensitive membrane. In the surfactant sensor, the sensitive film is
- formed from polyvinyl chloride plasticized with nitrophenyl octyl ether.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a surfactant sensor according to an embodiment of the present invention. In the figure, 1 is an electrode body in which a support tube 2 and a lower outer tube 3 are connected via an O-ring 4, and 5 is an electrode body. An internal electrode is housed in the main body 1, 6 is an internal liquid, 7 is a sensitive film made of PvC plasticized with o-NPOE and is attached to the detection end of the main body 1 to cover the opening, 8 is a cap, and 9 is a sensitive film. This is the lead wire.

Here, although there is no limitation on the composition of the sensitive film used in the present invention,
The blending ratio of PVC and o-NPOE is 0.1:5 by weight
It is preferable to use one having a ratio of 4:0.01 from the viewpoint of responsiveness to surfactants. In addition, the thickness of the sensitive film is 0.1
It is appropriate to set it to about 2 am.

Although the method for manufacturing the sensor of the present invention is not particularly limited, a method of dissolving PVC and 0-NPOE in a solvent, forming this solution into a film, and then vaporizing the solvent to form a film is preferably adopted. Ru.

Furthermore, there are no restrictions on the structure of the electrode body, the types of internal electrodes and internal liquid, and they can be appropriately selected depending on the substance to be measured and the like.

When measuring using the sensor of the present invention, a sample is brought into contact with the sensitive membrane. In this case, measurement can be carried out by immersing the detection end of the sensor in the sample solution, but when the surfactant concentration is low (below 10-bM/l), high sensitivity can be achieved by combining column concentration, etc. It is possible to aim for Note that the sensor of the present invention can also be used as a detector for a gas chromatograph.

Next, the present invention will be concretely illustrated by examples, but the present invention is not limited to the following examples.

Human blood ± 1g orthonitrophenyl octyl ether and 0.4
g of PVC powder is thoroughly dissolved in 10 ml of tetrahydrofuran. Next, this solution is transferred to a vetri dish (diameter 7 cm) and air-dried for 48 hours to volatilize tetradrofuran and obtain a sensitive membrane. Next, the sensitive membrane was cut out to a size of 6 ml in diameter, and this was adhered to the PVC outer tube 3 of the electrode body 1 shown in FIG. 1 using an adhesive prepared by dissolving PVC powder in tetrahydrofuran. 10-3M/A as internal liquid
Dodecyl sulfuric acid solution +10-'M/j! A sensor as shown in FIG. 1 was prepared using a sodium chloride solution and an Ag(l) electrode as the internal electrode 5.

Next, we investigated the basic characteristics of this sensor shown in (1) to (3) below.

■ Dodecyl sulfate ion (DS-
), both respond well to dodecyltrimethylammonium ion, which is a cationic surfactant ion, and for example, as shown in the calibration curve in Figure 2, the potential gradient for dodecyl sulfate ion at 25°C is 58.6 mV, linear region. is 1
0-'' to 10-6 M/A. Furthermore, as shown in the calibration curve of FIG. 3, it also responded well to dodecyltrimethylammonium ions.

Here, Table 1 shows the measurement results of the responsiveness to dodecyl sulfate ions at 25° C. of the sensor of the present invention and sensors using other sensitive membranes.

That is, compared to the sensor of Guch et al. mentioned above, the linear region is 10-' to 10-'M/! ! From 10-”
The potential gradient was improved from 50 mV to 58.6 mV. This potential gradient has a theoretical value of 5
This corresponds to 99.2% of 9.15 mV. In this case 〇−
Only the sensor using a membrane made of NPOE and PVC had a potential gradient of 58.6 mV, which was closest to the theoretical value, and the quantification range was the widest, from 10-6 to 10-''M#.Therefore,
With the adoption of o-NPOE, it can be said that an anionic surfactant sensor has become practical for the first time.

■ Response time The response speed of the sensor was investigated when the concentration of surfactant (sodium dodecyl sulfate) in the sample was varied.

The results are shown in Figure 4.

From the results shown in FIG. 4, it is recognized that the response takes about 5 seconds to both change from low concentration to high concentration and from high concentration to low concentration.

(2) pH characteristics The responsiveness of the sensor was investigated when the pH of the sample was varied. The results are shown in Figure 5.

From the results shown in FIG. 5, it is recognized that the electrode potential is not affected by the pH of the sample in the pH range of 1 to 7.

■ Selectivity The selectivity of this sensor for dodecyl sulfate ions was investigated using a mixed solvent method. The results are shown in Table 2.

Table 2 From the results in Table 1, it is found that the sensor of the present invention is hardly interfered with by inorganic anions, but responds with good sensitivity to other anionic surfactants. However, since it is extremely rare that several types of anionic surfactants are used in combination, there is no practical problem.

(2) Reproducibility In five repeated measurements, the standard deviation of the electrode potential was 0.99 mV when the concentration of dodecyl sulfate ion was 1 O-'M/β. This shows that the actual accuracy is ±3.9% in terms of concentration.

Next, the correlation between the measurement results obtained by this sensor and the measurement results obtained by the JIS method was investigated. In this case, prepare the DS-standard solution appropriately, prepare four samples, and use this sensor and the JIS method (
The respective DS-concentrations were measured by methylene blue spectrophotometry) and correlated.

The results are shown in Figure 6.

From the results shown in Figure 6, the measured values by the sensor of the present invention are JIS
It is recognized that there is a good correlation with the law. Therefore, the sensor of the present invention is practical as a simple measuring device for surfactants.

As explained above, the surfactant sensor of the present invention has a sensitive membrane made of polyvinyl chloride plasticized with 0-nitrophenyl octyl ether.
It exhibits a wide range of Nernst responses to anionic and amphoteric surfactants, and has a fast response speed, making it possible to easily and quickly measure ionic surfactants.

Moreover, the sensor of the present invention has the following advantages due to the above-described configuration.

■ Since the conventionally required ionic aggregates are not used, the membrane composition is reduced to orthonitrophenyl octyl ether and P.
Since it is simplified to a two-component system of VC and no time is required to synthesize the ionic association, the film forming time is greatly shortened to about 2/100 of that of the conventional method.

■ The surfactant concentration can be determined in a few seconds by simply dipping the sensor into the sample, so it can be used for process control of processes that use surfactants and as a sensor for continuous measurement devices for surfactants in wastewater. .

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional view showing an embodiment of the present invention, Figure 2 is a calibration curve when dodecyl sulfate ions are measured using the sensor of the present invention, and Figure 3 is a calibration curve when dodecyl trimethylammonium ions are measured using the same sensor. Fig. 4 is a graph showing the response of the sensor when the surfactant concentration in the sample is varied, and Fig. 5 is a graph showing the response of the sensor when the surfactant concentration in the sample is varied and the pH is varied. A graph showing the response of the sensor. Figure 6 is a graph showing the correlation between the measurement results of dodecyl sulfate ions by the sensor of the present invention and the measurement results by the JIS method. Figure 7 is a graph showing the case where tetrabutylammonium ions are measured by a conventional sensor. calibration curve,
FIG. 8 shows a detection ffi line when tetraphenylborate ions are measured by the same sensor. DESCRIPTION OF SYMBOLS 1... Electrode main body, 5... Internal electrode, 6... Internal liquid, 7... Sensitive membrane. Applicant: Denki Kagaku Keiki Co., Ltd. Representative: Patent attorney: Takashi Kojima Handling (
(effect) rental ≧ area (word) ・Electrode method (vt) 11og c

Claims (1)

[Claims] 1. A surfactant sensor in which a sensitive membrane is provided at the detection end of the electrode body containing an internal electrode and an internal liquid, and the surfactant concentration in the sample is detected by bringing the sample into contact with the sensitive membrane. A surfactant sensor, characterized in that the sensitive film is formed of polyvinyl chloride plasticized with o-nitrophenyl octyl ether.