RU2299432C1 - Method of determining qualitative composition of organic substances in environmental objects - Google Patents

Abstract

FIELD: analytical methods.

SUBSTANCE: when performing environmental and sanitary chemical investigations, organic substances in air-dry sample of a material are twice extracted with dichloromethane on sodium sulfate in glass column. Extracted substances are separated chromatographically in thin silica gel layer using hexane/carbon tetrachloride/ ethyl acetate mixture as eluent. Organic substances are then determined by comparing parameter characterizing position of chromatographic zone of substance, Rf, for fractions obtained by extraction with Rf for substances identified by chromato-mass-spectrometric technique.

EFFECT: increased information value of analyses.

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Description

The invention relates to the field of chemical analysis and can be used to determine the qualitative composition of organic substances in objects based on an organic matrix: in sediments of excess activated sludge from industrial and municipal biological treatment facilities, in bottom sediments of water bodies, in organic fertilizers and soils in environmental and sanitary -chemical studies.

The closest in technical essence to the claimed invention is a method for determining the content of organic matter of the soil, in which 10 g of soil is dried first in the air, and then at a temperature of 100-105 ° C for 1.5-2.0 hours, cooled and weighed. Then the dried soil is calcined in a muffle furnace at 400-450 ° C until the gray color disappears, cooled and weighed. The difference in weighing before and after calcination shows the content of organic matter in the sample [Rinkis G.Ya., Ramane Kh.K., Kunitskvya T.A. Soil and plant analysis methods. - Riga: Zinatne, 1987. - 174 p.]. The disadvantage of this method is its low information content, since the composition of the extracted substances remains unknown.

The technical result of the invention is to increase the information content of determining the qualitative composition of organic substances in environmental objects.

The technical result is achieved by the fact that organic substances are extracted from an air-dried sample of the material in a glass column on a layer of sodium sulfate with dichloromethane. The solvent is distilled off from the extract, the dry residue is dissolved in a mixture of diethyl ether and dichloromethane. Separation of substances in the extract is carried out by chromatography in a thin layer of silica gel using a mixture of hexane, carbon tetrachloride and ethyl acetate as an eluent. Chromatographic zones are developed under ultraviolet (UV) illumination and substances are identified by comparing R _{f of the} obtained fractions with R _{f of} substances identified by chromatography-mass spectrometry (ChMS).

When conducting a qualitative analysis of organic substances, silica gel was chosen as the sorbent for thin layer chromatography (TLC), which allows us to analyze a wide range of compounds: hydrocarbons (HC), alcohols, phenols, aldehydes, acids, amines, lipids, etc. The only independent parameter in TLC is composition of the mobile liquid phase (PZhF). For the separation of organic substances in the silica gel layer, the polarity of the solvents that make up the PCP, the presence of functional groups in the molecule of the analyzed substances, capable of forming hydrogen bonds with the active groups of the sorbent and with the functional groups of the PCP, are essential. Therefore, solvents with a dipole moment in the range of 0–4 dB were studied. This suggests the possibility of differentiated interaction with a sorbent and PZhF of a wide range of compounds, from nonpolar hydrocarbons to polar compounds with heteroatoms in the molecule. When choosing the optimal composition of the mobile liquid phase, the ΔR _f values between adjacent zones of fractions on the plate, the number and quality of fractions zones were taken into account. Studies have shown that in non-polar solvents (hexane, benzene) the separation is unsatisfactory. Even the introduction of polar solvents - ethyl acetate, acetic and formic acids, acetonitrile does not significantly affect the separation. However, the addition of carbon tetrachloride to hexane, a non-polar solvent, but capable of forming hydrogen bonds due to chlorine atoms, dramatically improves the quality of the separation. Therefore, the combination of hexane and carbon tetrachloride was chosen as the basis, which made it possible to obtain maximum separation. The introduction of ethyl acetate into this mixture improved stain quality.

The composition of the fractions was identified by the HMS method (Table 1). Using these data, it is possible to conduct a qualitative analysis only by TLC, which significantly reduces the analysis time and reduces its cost.

Table 1.
The composition of the fractions of the extract of excess activated sludge No. R _f in TCX The main substances contained in the fractions of sludge extract one 0.93 8-methoxyethyl phthalate and bromine derivatives of paraffins from C ₁₃ 2 0.82 butyl-8-methylnonylphthalate and homologues and isomers of paraffins from C ₁₃ 3 0.64 dimethoxyethyl phthalate and homologues and isomers of paraffins from C ₁₃ four 0.46 homologues and isomers of C ₁₃ paraffins and an admixture of butyl-8-methylnonylphthalate 5 0.35 butyl 2-ethylhexyl phthalate 6 0.23 butyl-8-methylnonylphthalate and homologues and isomers of paraffins from C ₁₃ 7 0.09 butyl 2-ethylhexyl phthalate, 8-methoxyethyl phthalate, dioseoctyl phthalate 8 0 2-dimethoxyethyl phthalate, diisooctyl phthalate, squalene

The values of R _f depend on the quality of the plate, the temperature of the mobile phase and the environment, the purity of the solvents and other conditions. The influence of the separation conditions was evaluated metrologically by choosing the R _f zones of the components of various objects from the experiments over a long period (Table 2). The table shows that the values of R _f in the selected PZhF are stably reproduced for both different samples of sludge and soils. Small values of the standard deviation of arithmetic mean values (S) and a small error (ε) in the determination of R _f indicate the correctness of the qualitative analysis.

Table 2.
Metrological evaluation of chromatograms with the number of determinations n = 5-9 (R _f - characterizes the position of the chromatographic zone of the compound, p = 0.95, ε - confidence interval, S - standard deviation of the arithmetic mean value of R _f ) No. Substance Gray forest soil IL OJSC "Salavatnefteorg-synthesis" WWS
p.Pryutovo R _f ± ε Sr R _f ± ε Sr R _f ± ε Sr one 8-Methoxyethyl phthalate and bromine derivatives of paraffins from C ₁₃ 0.91 ± 0.014 0.0122 0.92 ± 0.014 0.0173 0.92 ± 0.030 0.0122 2 Dimethoxyethyl phthalate, homologues and isomers of paraffins from C ₁₃ - - 0.67 ± 0.031 0,0389 0.67 ± 0.088 0,0354 3 Homologists and isomers of C ₁₃ paraffins and an admixture of butyl-8-methylnonylphthalate 0.41 ± 0.014 0.0112 0.43 ± 0.027 0,0253 0.44 ± 0.053 0.0212 four Butyl 2-ethylhexyl phthalate 0.33 ± 0.015 0.0123 0.34 ± 0.009 0.0112 0.33 ± 0.072 0,029 5 Butyl-8-methylnonylphthalate, homologues and isomers of paraffins from C ₁₃ 0.24 ± 0.011 0,0274 0.23 ± 0.017 0,0200 0.23 ± 0.039 0.0158 6 Butyl 2-ethylhexyl phthalate, 8-methoxyethyl phthalate, dioseoctyl phthalate 0.10 ± 0.022 0.0090 0.08 ± 0.008 0,0100 0.09 ± 0.009 0,0200 7 2-Dimethoxyethyl phthalate, diisooctyl phthalate, squalene 0 - 0 - 0 -

A method for determining the qualitative composition of organic substances in environmental objects is as follows. Take one of the environmental objects, for example, 0.5-1.0 g of excess activated sludge, dry it in air to an air-dry state, place it in a column on a layer of calcined sodium sulfate, pour 5 ml of dichloromethane and hold for 10-20 minutes until completely wetted. Then, the solvent is passed through the sample at a space velocity of 1-2 drops / sec. Processing the sample with dichloromethane is performed 2 times. The solvent was removed from the extract in a stream of nitrogen at room temperature. The dry residue is dissolved in 5-10 ml of a mixture of diethyl ether and dichloromethane (1: 1). The sludge extract was fractionated by TLC in a mixture of n-hexane, carbon tetrachloride and ethyl acetate.

Chromatographic zones exhibit UV illumination at a total wavelength of 186 and 253 nm and R _{f of} each fraction is calculated by the formula: R _f = L / 1, where L is the distance from the start line to the center of the zone, mm; 1 - distance from the start line to the front line of the solvent, mm Comparing R _{f the} obtained fractions with R _f substances in table 1, identify the substances that make up the sludge.

Example: 0.5 g of excess activated sludge of a biological treatment plant, dried in air to an air-dry state, is placed in a column on a layer of calcined sodium sulfate, 5 ml of dichloromethane are poured and incubated for 15 minutes until completely wetted. Then the column valve is opened and the solvent is passed through the sample at a space velocity of 1 drop / sec. Processing the sample with dichloromethane is performed 2 times. The extract is dried in a stream of nitrogen at room temperature. The dry residue is dissolved in 5 ml of a mixture of diethyl ether and dichloromethane (1: 1). The sludge extract was fractionated by TLC in a mixture of n-hexane, carbon tetrachloride and ethyl acetate. Chromatographic zones exhibit UV illumination at a total wavelength of 186 and 253 nm and R _{f of} each fraction is calculated by the formula: R _f = L / 1. For example, consider the calculation of R _{f of} some fractions for the sludge of OAO Salavatnefteorgsintez. The chromatogram measures the distance from the start line to the center of the zone and the distance from the start line to the front line of the solvent (mm).

1) L = 64 mm, l = 100 mm, R _f = 0.64. Comparing the obtained value of R _f with table 1 and 2, determine that it corresponds to the value of R _f = 0,67 ± 0,031. Therefore, this precipitate contains dimethoxyethyl phthalate and impurities of homologues and isomers of paraffins from C ₁₃ and higher.

2) L = 93, l = 100, R _f = 0.93. Comparing the obtained value of R _f with table 1 and 2, determine that it corresponds to the value of R _f = 0.92 ± 0.014. Therefore, this precipitate contains 8-methoxyethyl phthalate and an admixture of bromine derivatives of paraffins with the number of carbon atoms from C ₁₃ and higher.

When comparing chromatograms of different samples of excess activated sludge from industrial wastewater treatment plants, WWS from municipal biological treatment plants, chernozem and gray forest soil (Tables 3 and 4), one can clearly see how the composition of biogenic components of industrial sludge is enriched when the humification process is deepened as a result of composting and approaching the composition of soil humus. The qualitative compost of industrial sludge in the surface layer (25 cm) is close to the composition of gray forest soil. While the sludge located in sludge collectors and biological ponds of treatment facilities under a layer of water is not yet sufficiently humified. This suggests that humification is more intense under aerobic conditions, rather than anaerobic. Therefore, in order to detoxify sludge and prepare it for disposal by biosphere methods, preliminary dewatering and composting of sludge should be carried out.

Thus, a qualitative analysis technique has been developed to identify the composition of organic toxicants in environmental objects, which allows us to assess the degree of humification of these objects during their formation, storage and disposal by biospheric methods.

The advantage of the proposed method for determining the qualitative composition of organic toxicants in environmental objects in comparison with the known is a significant increase in the information content of the method, which allows to characterize the degree of humification of the object.

The method is technically prepared for use in the national economy.

Claims (1)

A method for determining the qualitative composition of organic substances in environmental objects, including preliminary drying of a material sample, characterized in that the sample is extracted in a glass column on a layer of sodium sulfate twice with dichloromethane, separated into fractions by thin layer chromatography in a mixture of hexane, carbon tetrachloride, ethyl acetate and the determination of organic substances is carried out by comparing the parameter characterizing the position of the chromatographic zone substance, R _f obtained fractions with R _f substances id ntifitsirovannyh method hromatomasspektrometrii.