SU1583822A1 - Method of determining surfactants - Google Patents

Abstract

This invention relates to analytical chemistry, in particular, to the determination of surfactants in process solutions for the production of chemical fibers. The purpose of the invention is to improve the accuracy and expansion of the range of surfactants analyzed. The goal is achieved by the fact that surfactants are precipitated with a 0.005-0.02 M aqueous solution of a heteropoly acid (phosphorus tungsten, phosphomolybdenum, silicon tungsten, silicon molybdenum). The end point of the titration is determined by an amperometric method using a platinum electrode. It is also possible to determine DMSO, DMA, nitrogen- and sulfur-containing compounds. 1 hp f-ly, 1 ill., 1 tab.

Description

The invention relates to analytical chemistry, in particular, to the determination of surface-active substances (surfactants) in technological solutions of chemical wave production and other industries that use surfactants.

The purpose of the invention is to improve the accuracy and the expansion of the range of the analyzed surface-active substances (surfactants).

The drawing shows current-voltage curves for the recovery of phosphorus-tungsten acid.

The surfactant is deposited in an acidic medium with an aqueous solution of a heteropoly acid, and the final titration point is determined by the amperometric method using a platinum electrode. Heteropolyacids (HPA), when reconstituted on the microplatinum electrode, produce a limiting current wave, which linearly increases with increasing acid concentration.

The addition of surfactants (OP-10, OC-20, sintanol, PEG with different molecular weights from 300 to 40,000) leads to a decrease in the total current limit, which is proportional to the content of the surfactant introduced. When the acid is injected back into the solution containing the surfactant, the waves of the limiting current (the current during the amlerometric indication) appear only after the surfactant has completely reacted with the injected acid. 0.1–0.2 M solutions of HCI, H2SO4, Na2SO4 + H-SO / j can be used as background electrolytes. Standard solutions of heteropolyacids are prepared according to an exact weight after their water content is established using Fisher reagent. The range of concentrations of acids was determined by the content of surfactants in the objects under study and was 0.005-0.02 M. Objects of the analysis were model solutions of surfactants in water in the form of 0.1 SP 00

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1.0% solutions of OP-10, OC-20. synanol, PEG with various molecular weights from 300 to 40,000, as well as technological solutions for the production of chemical fibers containing dimethylacetamide, dimethylformamide, dimethyl sulfoxide and other nitrogen- and sulfur-containing compounds. The indication of the end point of the titration was carried out with the amperometric method at the constant potential at the site of the limiting current. The voltage – current curves were removed on a PU-1 semi-graph.

For example 1. In a 0.1 M HCI solution, 20 µl of a model 0.1% OP-10 solution are injected. Amperometric titration was carried out with a 0.005 M solution of phosphoric acid. The surfactant concentration is found from the calibration curve of the dependence of the acid volume on the surfactant content. The analysis data are given in the table.

Example 2. In a 0.2 M solution of sulfuric acid, 20 µl of a model O J% solution of OS 20 was injected. Then, as in Example 1 (phosphomolybdic acid),

PRI me R 3. In a 0.2 M solution of HCI, 20 µl of a model 0.1% solution of syntanol was injected. Further, as in example 1 (silicon-tungstic acid).

Example 4. A 0.1 M solution of sulfuric acid was injected with 20 µl of a model 0.1% solution of ELEG (). Further, as in example 1 (silicic molybdenum acid).

. Example 5, B 0.1 M solution of N32S04 + 0.1 M H2S04 was introduced with 20 µl of the model 0.1% PEV solution (). Further, as in example 1.

Example 6. In a 0.1 M solution of sulfuric acid, 20 µl of a model 0.1% PEG solution () was injected. Further, as in example 1 (phosphotungstic acid).

Example 7: In a 0.2 M HCI solution, 20 µl of a PEG model solution (M 40000) of a 0.1% strength solution is injected. Further, as in example 1 (phosphomolybdic acid).

Example 8. 20-50 ml of a technological solution containing 10-40% sulphates (sodium sulphate and sulfuric acid) and PEG-35 () are taken. Amperometric titration is carried out with a 0.02-0.01 M solution of phosphorotungstic acid. Further, as in example 1.

The results of determining the content of surfactants in aqueous solutions are given in the table.

The method allows the determination of PEG in a wide range of molecular weights. The analysis time does not exceed 20 minutes.

Claims (2)

1. A method for determining surfactants by precipitating them with a solution of heteropoly acids with an electrochemical indication of the end point of the titration, characterized in that, in order to increase the accuracy of the analysis and expand the range of the surfactants being analyzed, their deposition is carried out with 0.005-0.02 M aqueous a solution of a heteropoly acid, and the end point of the titration is determined by the amperometric method using a platinum electrode. 2. A method according to claim 1, characterized in that phosphorotungstic, phosphomolybdic, silicotungstic, molybdic acids are used as the heteropoly acid. 1 μA