SU1755134A1 - Method of quantitative determination of cation-type surfactants - Google Patents

Abstract

Use: in analytical chemistry. The essence of the invention is that in the method of quantitative dividing of the kationic surfactants, the analyzed solution is treated with an alkaline solution of 4-diethylaminophthalhydrazine in the presence of hydrogen peroxide and a copper (II) salt solution, followed by quantitative recording of the chemiluminescence intensity. The method allows a 14-fold increase in the sensitivity of the determination of cationic surfactants to 0.035 µg / ml. 2 tab.

Description

The invention relates to analytical chemistry and relates to the determination of cationic surfactants (CPAS) when they are contained in a solution of 0.035-10 mg / l, which can be used in the analysis of environmental objects, natural and waste waters, food products, detergents , waste control of the textile industry, extraction technology.

A known method for determining the CPAS by precipitating the last reagents of Dragendorf (barium iodic iodide), extracting the complex formed in chloroform, followed by photometry of the extract.

The disadvantages of the method are low sensitivity, laboriousness associated with the presence of an extraction operation, the need to use a toxic organic solvent.

A known group of methods for the determination of CPAS, based on the extraction with an organic solvent of the associations of CPAS with anions of acid dyes, followed by photometry of the extract. The use of acid dyes for the determination of microquatities of higher quaternary ammonium pains in the presence of macroscopic amounts of first secondary and tertiary amines.

The sensitivity of the listed methods is fundamentally limited by the capabilities of the spectrophotometric method of analysis and does not exceed 0.1 mg / l, which makes it impossible to apply them to determine

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The CPAC with a content at and below the MPC (MPC of alkylbenzyldimethyl ammonium chloride is 0.1 μg / ml).

The closest in technical essence and the achieved result to the proposed prototype method is the determination of the CPAS by treating the aqueous solution of the analyte with bromophenol blue mixed with polyethylene glycol -30 in a molar ratio of bromophenol blue and monooctyl ether polyethylene glycol-30 equal to 1: (10 - 20) at pH 3.9 - 4.0, followed by photometry of the colored compound. N

The sensitivity of the method (0.2 µg / ml) also does not allow to analyze the CSEL when they are kept at and below the MPC,

The purpose of the method is to increase the sensitivity of the determination of cationic surfactants.

This goal is achieved by treating the sample with an organic reagent 4-diethylamino phthalhydrate (DEAFG) in an alkaline medium in the presence of hydrogen peroxide and copper (II) salt, followed by measuring the intensity of chemiluminescence after 30 s.

Thus, the distinguishing features of the proposed method are: use of 4-diethylamino-phthalhydrazide as an organic reagent; determination at pH 10–11 in the presence of hydrogen peroxide and copper (II) salt at a concentration of (2–4) M; determination of CPAS by measuring the chemiluminescence intensity of the solution.

The use of 4-diethylaminophthalhydrazide in a mixture with hydrogen peroxide and a copper (II) salt in the determination of CPAS is due to the obvious fact that the chemiluminescence intensity of the solutions changes in the presence of the CSAS.

The use of these distinctive features makes it possible to determine the CSEL with their content of 0.035-10 µg / ml with a relative error of 25-2%.

Chemiluminescent determination was carried out, as a rule, using a 20 ml cuvette into which a DEAPH solution was introduced, bidistilled water, based on a total volume of 5 ml, an aliquot of the analyzed surfactant solution, KOH solutions, and copper (II) salt. The latter were injected with a solution of hydrogen peroxide, mixed, and the intensity of luminescence after 30 was measured using a photomultiplier. The following concentrations of DEAFG (2-5) M hydrogen peroxide are (2-3) .pH 10-11.

To obtain comparable results, a determination was made by a known method.

Example 1 (prototype), In a 25 ml volumetric flask, 5 ml of acetate buffer solution with a pH of 3.95 and 5 ml of a 2-M solution of bromophenol blue, 1 ml of 10 2 were placed

M aqueous solution of monooctyl ether of polyethylene glycol-30 and an aliquot of the analyzed solution containing the surfactant. The solution was brought to the mark with water and the decrease in light absorption was measured.

the obtained solution at А 595 nm in a cuvette with I 2 cm relative to a comparison solution that does not contain a PSAC. The content of CPAS in the analyzed solution was determined according to a graduated graph. The construction of the calibration curve was carried out in a similar way using a standard solution determined by the surfactant. The content of the cationic surfactant in the final volume when constructing a calibration grfik should be 5-140 µg.

Thus, from Example 1 it can be seen that the known method allows determining PSECs with a content of 0.2-5.5 µg / ml in a solution. The linear dynamic range of the determination is 1.3 times the order.

Example 2. The definition of the claimed method.

In the cuvette introduced 0.5 ml of 2 M solution DEAFG, 0.3 ml of M solution of KOH,

0.5 ml of a 2-M solution of copper nitrate (I), an aliquot of the analyzed solution of the surfactant. 0.5 ml of 2 M hydrogen peroxide solution was injected last, stirred, and the luminescence intensity was measured after 30 s.

The content of CPAS was determined from a graduation graph built in biographic coordinates: luminescence intensity — concentration of CPAS. The construction of the calibration curve was performed

Similarly, using a standard solution of CPAS. The content of CPAS in plotting should be 0.035 µg / ml.

Thus, from table. 1 shows that the proposed method can be used to determine various CPAS with their content of 0.035 - 10 μg / ml with a relative error of 25 - 2%. The linear range of the calibration curve is 2.3 times.

Example 3. In the cuvette was injected all the components, as in example 2, except for the solution of copper nitrate (P), instead of which was introduced a solution of copper sulfate (P). The intensity of the glow was measured after 30 s. The contents of the cationic surfactants were found on the calibration curve. The detection sensitivity is 0.035 µg / ml. The linearity of the calibration curve is maintained up to 10 µg / ml.

From example 3 it can be seen that solutions of both nitrate and sulphate can be used to determine the BSEC.

Example 4. The rationale for the concentration range of copper nitrate (I). In the cuvette was injected all the components as in example 2, except for the solution of copper nitrate, which was injected in the quantities listed in table. 2. The solution was stirred and the luminescence intensity was measured after 30 s. The contents of the cationic surfactants were found on the calibration curve. The results are shown in Table. 2

From tab. 2 that when the concentration of copper is less than 2 10 M, the sensitivity of determination of the PSEL does not decrease, however, the linear dynamic range of the calibration graph significantly decreases from 2.3 times (at a concentration of copper (II) 2 M) to 1 (concentration of copper-1 -10 M) and 0.5 (copper (M) concentration - 5-M). Increasing the salt concentration of copper (P) leads to a decrease in sensitivity of two or more times.

Thus, the implementation of the claimed method for determining the PSECs when using DEAFG in a mixture with hydrogen peroxide and copper salt (I) allows one to achieve the objective of the invention; the output beyond the stated interval does not lead to the achievement of the objective of the invention.

The use of the inventive method for the determination of CPAS gives a positive effect compared to the known method, which is expressed as follows: an increase in the sensitivity of the method (the detection limit is 0.035 µg / ml instead of 0.2 µg / ml according to the prototype);

- increase in the order of the linear dynamic range of the calibration curve (2.3 order, together with 1.3 of the prototype).

Practical use of the proposed method for determining the CCAS can significantly simplify the analysis of objects containing CCAS in and below the MPC, increasing the reliability of the results obtained.

Claims (1)

Invention Formula The method of quantitative determination of cationic surfactants, including the treatment of an aqueous solution of the analyte organic reagent, the registration of the spectral characteristics of the solution, the value of which carries out the determination, characterized in that, in order to increase the sensitivity, as the organic reagent is used 4-diethylaminophthalhydrazide, the sample is treated with an alkaline medium in the presence of hydrogen peroxide and (2-4) M solution of copper (II) salt, and the intensity of the chemiluminescent glow of the resulting solution is measured. Table Statistical processing of the results of determination of CPAS in model solutions (concentrations of DEAFG, hydrogen peroxide, and copper (II) nitrate are, respectively, M. 2 -10 5, 2-, 2- pH 10.6, p-6,, 95) Table 2 The results of the study of the effect of copper (II) nitrate concentration on the sensitivity and range of detectable concentrations of CPAS (the concentration of DEAPH and hydrogen peroxide are, respectively, M: 2, 2, pH 10.6) Continuation of table 1