RU2303476C2 - Method of isolating organics from aqueous media via extraction combined with freezing - Google Patents

Abstract

FIELD: physicochemical methods.

SUBSTANCE: invention is designed for use in analytical chemistry, pharmacology, and other areas and consists in the following. To the sample containing target organic substances, an organic solvent is added, after which sample is frozen. As freezing advances, organic solvent together with extracted organic substances is separated into discrete liquid phase. Extract phase is separated when aqueous part of the sample is still in frozen state.

EFFECT: avoided use of intricate equipment and multiple stages, and reduced power expenses.

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Description

The invention relates to hydrochemistry, analytical chemistry, biochemistry, ecology, cryomedicine, pharmacology, forensic medicine, forensic science and can be used to isolate both natural and synthetic, technogenic organic substances from aqueous media, aqueous biological fluids (urine, blood, etc. ) and aqueous extracts-extracts of various objects.

A known method of separation of organic substances, combining extraction and freezing [1]. Dissolved organic compounds are transferred from an aqueous medium pre-cooled to a temperature close to freezing point to a water-insoluble liquefied light hydrocarbon (n-butane, isobutane, propane) with constant stirring until the water crystallizes completely.

However, this method [1] has a number of serious disadvantages:

- the process requires sophisticated technological equipment, special equipment for pre-cooling-liquefaction of butane gas (propane), a temperature control system and thermal insulation, constant mixing, etc .;

- the extraction efficiency substantially depends on the experimental conditions, the intensity of dispersion of the organic extractant in the volume of crystallized water, etc .;

- multi-stage, significant labor and energy costs.

A known method [2] of wastewater treatment from highly concentrated finely divided organic and mineral impurities, including synthetic and semi-synthetic cutting fluids, in which, after chemical decomposition of the composition with phosphoric acid at pH 4.6 and the addition of aliphatic alcohols, the effect of separation of the organic phase water is obtained by freezing to (-3) - (- 4) ° С followed by thawing of the mixture to 0 - (+ 5) ° С.

However, this method [2] has a number of serious disadvantages:

- the process requires complex technological equipment, special equipment for cooling and liquefying ammonia, a temperature control system and thermal insulation, pipelines, containers for various purposes, etc .;

- multi-stage, significant labor and energy costs;

- cannot be used to isolate natural hydrophilic organic substances and medical preparations from biological fluids, the concentrations of which in the initial sample are usually very small (0.5 ÷ 10 mg% - organic acids in blood and urine [3], less than 10 mg / l - therapeutic concentrations of most drugs in the blood [4]), since the principle of isolating the target substances and the water-soluble extractant of isopropanol as a separate organic phase during freezing-thawing is based on the high content of excreted organic impurities in the initial sample (4% by volume), which ".. together with the extractant after thawing float up ..." to the surface of liquid water in the tank for separation of the mixture;

- not applicable for working with small volumes of the original sample, for example, in the analysis of biological fluids (blood, urine, etc.), where the sample volume usually does not exceed several milliliters;

- it is limitedly applicable in the analysis of organic matter of natural and mineral waters, since it allows the use of only water-insoluble alcohols in this case.

The technical result is the improvement of economic indicators and the exclusion of multi-stage.

This is achieved by the fact that the target organic substances are extracted from water, aqueous biological fluids, aqueous extracts of various objects by first adding a soluble organic extractant (acetonitrile, acetone, diethyl ether, etc.) to the sample volume and then cooling the prepared solution until water crystallizes. parts. As a result, the extracted organic substances pass into the added organic solvent released into the separate liquid phase on the surface of solid ice. The resulting liquid organic extract with the target components is separated from the frozen portion of the sample. During thawing of the solid part of the sample and repeated freezing, it is again released into the liquid phase: the remaining part of the organic solvent containing extractable components. The number of “defrost-freeze” cycles to increase the degree of extraction of the target substances depends on the volume and physico-chemical properties of the added extractant.

Example 1

A 38 g water sample containing acetic and propionic acids at concentrations of 11.4 μg / g and 10.7 μg / g, respectively, was placed in a glass bottle with a screw cap with a capacity of 50 cm ³ . Added 2 cm ^{3 of} chemically pure chromatography grade acetonitrile (grade 6, TU 6-09-06-1099-83). Sealing the bottle with a screw cap, the contents were mixed until dissolved. The resulting solution was placed in the freezer of the Saratov household refrigerator (temperature -15 ± 1 ° С). After crystallization of the aqueous part of the sample, a layer of the liquid phase of the organic solvent formed on the ice surface, which was separated by decantation into a separate tube. The mass of the extract was 0.254 g. The method of gas-liquid chromatography established the content of organic acids in the extract: acetic acid - 77.0 μg / g, propionic acid - 198.0 μg / g.

The remaining solid part of the sample (ice) was thawed at room temperature, mixed and again placed in the freezer of a domestic refrigerator. After crystallization of the aqueous part, an acetonitrile liquid layer again formed on the ice surface. The mass of the extract was 0.260 g, and the concentration of organic acids in it according to GLC analysis, respectively, was 240.0 μg / g acetic and 267.5 μg / g propionic.

Example 2

25.5 g of morning urine of patient B., 10 g of distilled water and 2 cm ^{3 of} chemically pure chromatography grade (grade 6, TU 6-09-06) ^were placed in the first vial (sample) with a screw cap with a capacity of 100 cm ³ -1099-83). In a second similar bottle (sample with an additive), 25.5 g of morning urine of patient B., 9.8 g of distilled water, 0.2 g of a standard solution of organic acids with a concentration of acetic 2167 μg / g and propionic 2030 μg / g were placed, and also 2 cm ^{3 of} chemically pure chromatographic grade acetonitrile (grade 6, TU 6-09-06-1099-83). The bottles were hermetically sealed with screw caps. The contents were mixed by shaking. Samples were placed in the freezer of the Saratov refrigerator (temperature -15 ± 1 ° С). After crystallization of the water portion of the test samples from the ice surface by decantation, the liquid organic phase was collected. The masses of extracts were, respectively, in the first bottle (sample) - 0.186 g, in the second (sample with additive) - 0.234 g. As a result of GLC study, the content of organic acids was established:

- in the first extract (sample), the concentration of acetic acid is 26.0 μg / g, propionic 11.0 μg / g;

- in the second extract (sample with additive), the concentration of acetic acid is 39.0 μg / g, propionic 59.0 μg / g.

The remaining solid part of the sample was thawed and, having mixed, was again placed in the freezer of a domestic refrigerator. After crystallization of the aqueous part of the sample from the first bottle by decantation, 0.306 g of organic extract was obtained, from the second, 0.202 g. The concentration of organic acids, as shown by GLC analysis, was, respectively:

- in the extract from the first bottle (sample) of acetic 18.0 μg / g, propionic 22.1 μg / g,

- in the extract from the second bottle (sample with the addition) of acetic acid 62.1 μg / g, propionic 29.9 μg / g.

Example 3

In a penicillin vial with a capacity of 15 cm ³ , 1 cm ^{3 of} the blood serum of patient C was added. 0.2 g of a standard solution of sodium benzoate 169.0 μg / g was added. The contents were mixed and 2 cm ^{3 of a} 50% aqueous trichloroacetic acid solution was added to sediment proteins. . After thoroughly mixing, 1 cm ^{3 of} acetonitrile was added. Again mixed and placed in the freezer of a domestic refrigerator "Saratov" (temperature -15 ± 1 ° C). After the aqueous portion of the sample froze, an organic transparent layer of the acetonitrile liquid extract was separated by decantation. Its mass was 0.287 g. Using high performance liquid chromatography, the content of benzoic acid in the extract was found to be 21.9 μg / g.

Example 4

A urine sample in an amount of 8 ml with an oxazepam content of 5 ÷ 10 μg / ml and phenazepam 16 ÷ 32 μg / ml is placed in a penicillin vial with a capacity of 15 ml. Add 2 ml of diethyl ether, tightly close with a plastic stopper and mix thoroughly. 0.4 ml of acetonitrile is added to the vial and, having closed with a plastic stopper, placed in the freezer of the refrigerator (temperature minus 14-18 ° C) to freeze the aqueous part of the resulting mixture. After the formation of a solid phase of ice in the lower part of the bottle, the released upper liquid layer of diethyl ether and acetonitrile (about 1.5-2 ml) is completely poured into another penicillin bottle. The remaining ice part of the sample is allowed to melt at room temperature, a new portion of diethyl ether is added in an amount of 0.5 ml, after stirring and adding 0.2 ml of acetonitrile, it is subjected to an additional freezing cycle, again placed in the freezer of the refrigerator. After freezing the water portion of the sample, the liquid organic extract released above the ice surface is decanted into the first portion of the extract. The procedure for additional extraction with 0.5 ml of ether and 0.2 ml of acetonitrile is repeated. Solvents after three times extraction from the combined extract are removed by evaporation in a stream of air, regulating its intensity and avoiding moisture condensation. The dry residue is dissolved in 100 μl of acetonitrile and sent for research using high performance liquid chromatography with UV detection (HPLC). The degree of extraction from the urine of oxazepam is from 60 to 77%, phenazepam is from 78 to 81%. The sensitivity of the method (for detection at a wavelength of 230 nm, the dosed sample volume into the injector of the chromatograph 10 μl) is not worse than 0.5 μg for oxazepam and 2.0 μg for phenazepam of benzodiazepine in the analytical sample.

The proposed method allows you to:

- perform direct one-stage extraction of dissolved organic substances in solvents miscible with water (acetonitrile, acetone, diethyl ether, etc.),

- reduce material, energy and labor costs.

Information sources

1. A.A. Rusinova, Yu.M. Polezhaev, A.I. Matern. Concentration of solutions by freezing. Analytics and Control, 1999, No. 4, pp. 4-10.

2. V.T. Pismenko. E.A. Kareev, L.I. Buldakovskaya. The method of decomposition of synthetic and semi-synthetic coolant. Patent RU 2129990 (Cl. C02F 1/26, С10М 175/04), 1999, 6с.

3. Biochemical research methods in the clinic. (Handbook) Ed. Acad. A.A. Pokrovsky, Moscow: Medicine, 1969, p. 596.

4. S.K. Eremin, B.N. Izotov, N.V. Veselovskaya. Analysis of narcotic substances. Manual for chemical tox. analysis of drugs and other intoxicants. M.: Thought, 1993, p. 266.

Claims (1)

A method of extracting organic substances from aqueous media, including freezing the aqueous portion and extracting the dissolved compounds into an added water-soluble organic solvent, which is released into a separate liquid phase during the freezing process, characterized in that the resulting organic extract is separated off when the aqueous portion is frozen.