SU1557495A1 - Method of determining trihalideacetates - Google Patents

Abstract

This invention relates to the analytical chemistry of acetic acid derivatives. The purpose of the invention is to increase the selectivity of the determination of trihaloacetate. For this, an aqueous solution of the analyte is treated with toluene solution of picrate octyloctadecylammonium with a concentration of 1 ^. 10 ^-3 mol / l. 1 tab.

Description

This invention relates to analytical chemistry, in particular, to methods for determining halogen-containing acetic anions with the general formula CF3COO.

The aim of the invention is to increase the selectivity of the determination of trihaloacetate,

The method is carried out as follows.

The test solution is treated with a liquid anion exchanger — a toluene solution of picrate octyloctadecylammonium (HERE) C i J7CnHJ7NH2 ... P i c, photometreize the equilibrium water phase and determine the concentration of the analyzed anion according to a calibration graph. Toluene solutions of the indicated ion exchanger are selectively extracted with anions of trihaloacetate kz aqueous solutions. Other solvents like octane, decane cannot

be used due to the low solubility of ion exchangers. The use of higher alcohols and chloroform as solvents does not lead to a positive effect due to the property of selectively extracting haloacetates. In addition, a positive effect is achieved only when using a salt of the secondary amine.

Example. 10 ml of 1 mol / l picrata OODA and solutions of varying concentrations of trihaloacetate against the background of acetate buffer solution with pH 4.0 are introduced into test tubes with ground plugs. Separately put idle experience. The volumes of the aqueous phases should be 10 ml. The tubes are shaken for 2–3 min. After separation of the phases, the lower aqueous phase is pipetted, filtered through a filter paper and photometrized

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spectrophotometer At a wavelength of 410 nm in a cuvette 1 cm relative to the blank solution. According to the data obtained, a calibration curve is constructed in the coordinates: A (optical density) - C (concentration of trihalide acetate in mol / l, mg / l, etc.).

When analyzing the sample solution, an aliquot portion (1-4 ml) is taken into a tube with a ground cork, add acetate buffer solution at pH 4.0, distilled water to 10 ml, 10 ml of extractant (mole / l picrate OODA) winds, the aqueous phase is taken, filtered and photometrized at 410 nm in a cuvette of 1 cm. The concentration of trihaloacetate is determined according to a calibration curve.

Preparation of a toluene extractant solution: 0.19 g of octylocta-decylamine is dissolved in toluene, the solution is transferred to a 500 ml measuring flask, and the solution is taken up to the mark with toluene. Separately, a solution of picrate sodium 1 mol / l is prepared against the background of acetate buffer solution with pH 4.0. To convert the amine to the picrate salt, equal volumes of the toluene solution of the amine and aqueous sodium picrate are shaken for 3-5 minutes in a separatory funnel. After separation of the phases, the lower aqueous phase is discarded and the organic phase is treated with a new sodium picrate solution. The obtained yellow organic phase is washed in a separating funnel 2-3 times with acetate buffer solution with pH 4.0, filtered and placed in a flask with a ground up stopper. The resulting solution has a concentration of mol / l and can be used as an extractant for the ext

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photometric determination of trihaloacetate.

The selectivity of the proposed method was evaluated in terms of the selectivity factor (Φ) —the limiting weight ratio impurity: the main substance, at which the error of determination is 10 rel.%. Trifluoro-, trichloro-, tribromoacetate anions were determined in the presence of hydrophobic perchlorate and rhodanide ions.

The table shows the selectivity factors for the determination of trihaloacetate in the presence of perchlorate- and rhodanide anions by known (Φ and pre- (L)) methods.

As can be seen from the table, the use of picrate octyloctadecylammonium as an extractant makes it possible to increase the selectivity factors by a factor of 60,666 times and, therefore, makes it possible to determine trihaloacetate in the presence of an excess of interfering anions.

Claims (1)

Invention Formula A method for determining trihalide acetates, which includes treating an aqueous solution of an analyte with a solution of pirate salt of a liquid anion exchanger in an organic solvent, separating the equilibrium aqueous phase, measuring its optical density, and determining the analyte concentration according to a calibration graph, characterized in that, in order to increase the selectivity of the determination, the solution analyzed substances are treated with toluene solution of picrate of octyloctadecylammonium with a concentration of 1 mol / l.