UA37555C2 - Method for determining the content of phosgene - Google Patents

Abstract

The present invention relates to analytic chemistry, specifically to a method for determining the content of phosgene in air, gaseous products produced in combustion and thermal destruction of different materials, and organic solvents. The proposed method for determining the content of phosgene consists in treating the sample to be analyzed by reagent that is sensitive to phosgene. As the said reagent, mix of piperidine with chloroform is used, with the ratio of 1:80 to 1:10 between the volume contents of the said components. To determine the content of phosgene, a gas chromatograph with a flame-ionization detector is used. Phenantrene is used as the reference substance. The proposed method provide the possibility to improve the selectivity, decrease the relative error, and increase the permitted storage period of the sample when determining the content of phosgene.

Description

Description of the invention

The invention relates to the field of analytical chemistry, namely to methods of quantitative determination of phosgene in 2 air, in particular in gaseous products of combustion and thermal destruction of various materials or in organic solvents, and can be used in many branches of the national economy.

There is a known method of determining phosgene by treating the analyzed sample with norsulfasol and sodium nitrite in an acetone solution (see Perehud E.A., Gernet B.V. Chemical analysis of air of industrial enterprises.

L., "Chemistry", 1970, p. 76-77).

The results of the determination of phosgene in the presence of carbon dioxide in the air are obtained with a large measurement error due to the interaction of carbon dioxide with the reagents used. In the products of thermal destruction, the concentration of carbon dioxide always significantly exceeds its content in the air, which makes it impossible to determine phosgene by the specified method. Diisocyanates, chlorine, hydrogen chloride accompanying phosgene also interfere with the determination of the latter by a known method. 12 The closest in technical terms is the method of quantitative determination of phosgene in air by passing the analyzed sample through a chromogenic reagent followed by photometry of the obtained colored solution, in which, in order to increase the sensitivity, selectivity and reproducibility of the method, the chromogenic reagent is a mixture containing 55-56bo6.95 of pyridine, 5-bob.95 aniline and up to 100o6.95 acetic acid. The relative standard deviation when determining phosgene in air is within 0.240-0.050 with a permissible deviation of 0.250 (see Auth. svid. USSR Mo1029054 A, cl. 01M21/78, 1983). The method is characterized by the possibility of determining phosgene in the presence of hydrogen chloride and chlorine in the amount of no more than 2.5 mg/m 3 and the stability of the results when the sample is stored for 3 hours.

The results of determining the amount of phosgene by the known method will be insufficiently accurate in the presence of hydrocyanic anhydrides (chlorocyanide and bromine) and carboxylic acids (for example, with 29 acetyl chloride), which are often present in the air environment along with phosgene. Gee)

The effect of impurities, manifested in a significant increase in the optical density of the analyzed solution, is due to the reaction of the indicated halogen anhydrides with the chromogenic reagent, which proceeds with the formation of a colored polymethine form. Since similar products of the reaction with the chromogenic reagent form phosgene, this leads to an overestimation of the results of the photometric analysis. Insufficient stability of 3o photometric characteristics over time is due to high requirements for the purity of reagents. The possibility of moisture and impurities entering the chromogenic reagent, which almost always accompany phosgene in the combustion products of polymeric materials (for example, acetic acid, hydrogen chloride, etc.), increases the measurement error due to changes in the pH of the medium and the ratio of components in the chromogenic reagent. uh-

The invention is based on the task of creating a method for the quantitative determination of phosgene by selecting an analyzed sample and treating it with a new reagent called phosgene, and determining the reaction product using a gas chromatographic method using an internal standard to ensure high selectivity of the method, stability of results over time and reduce measurement error.

The problem is solved due to the fact that in the method, which includes the selection of the analyzed sample and its treatment with a phosgene reagent, a mixture of piperidine and chloroform is used as a reagent in a volume ratio ranging from 1:80 to 1: 10 and determine phosgene by the gas chromatographic method using a flame ionization detector using the internal standard of phenanthrene. :z" Based on the conducted research based on the sources of patent and scientific and technical literature, it can be concluded that the set of essential features is new and allows to ensure the high selectivity of the method, the stability of the results over time and reduce the measurement error. o 395 The proposed method is based on the formation of the product of the interaction of operidine with phosgene 1,1-carbonyldi(1-piperidyl) (hereinafter KDP): -и СОСИ» 4С5НИОМН-х(СеНиоМ)»СО2С5НИоМНОНе у. sl With an excess of piperidine, the reaction proceeds with a quantitative yield and a sufficient speed under normal conditions. The selected ratio of piperidine to chloroform in the reagent provides an excess of piperidine even 1 50, provided that all possible impurities reacting with the latter are present in the analyzed sample. The resulting product of KDP dissolves well in chloroform, is non-volatile and chemically resistant, is well stored and remains stable for three days. The chromatographic method of analysis allows to selectively determine the product of the reaction of phosgene with piperidine (KDP). The use of the internal standard of phenanthrene allows to significantly reduce the measurement error.

The method of quantitative determination of phosgene in air or, if necessary, in organic solvents (F) is carried out as follows. A gas-air mixture with a volumetric flow rate of 0.2 dm/min is passed through. through an absorbent vessel with a porous plate containing 10 cm of the reagent (a mixture of piperidine and chloroform in a volume ratio of 1:80 to 1:10). Or do they add a defined volume of the analyzed sample containing phosgene in an organic solvent to 10 cm? reagent for phosgene and mix thoroughly. Take 0.9 cm? of the resulting solution and add 0.1 cm? phenanthrene solution. Quantitative determination of phosgene is carried out by the chromatographic method on a chromatograph of the LHM - 8MD type using a flame ionization detector and a differential gas supply system according to the equation of the calibration characteristic.

The calibration characteristic is set as follows. KDP is synthesized by the interaction of phosgene with a 65% excess of piperidine in toluene. For this, 50 g of 1595 solution of phosgene (0.0758 mol) in toluene is introduced into a round-bottomed flask with a dropper and a mechanical stirrer. Then, with stirring, slowly add a solution of 38.7 g (0.455 mol) of piperidine in HOcm? toluene. The formed precipitate of piperidine chlorhydrate is separated on a Schott filter, toluene and excess piperidine are driven off under the vacuum of a water jet pump, heating in a water bath (907). The resulting final product of 1,1-carbonyl(1-piperidyl) is purified by vacuum distillation. T. kip. 148-1507"С/ 15mm of Hg, t. pl. 44-47"С. The molecular weight of C 44H20M»O is 196.29.

Calculated: C 67.3; H 10.27; M 14.27. Found because: C 67.2; H 10.4; M 14.0. Output 12.2 g.

The equivalent concentration of phosgene (C) is calculated by the formula:

C-SkdpOoMf/Mkdp (1) where Skdp is the concentration of KDP, μg/cm;

Mf/Mkdp - the ratio of the molecular weight of phosgene and KDP.

Prepare model solutions of KDP (with an equivalent concentration of phosgene bBOmkg/cm") and phenanthrene (with a concentration of 136bOmkg/cm?) in a mixture of piperidine and chloroform. To obtain a calibration characteristic of 75, nine series of calibration solutions are prepared, which cover the range of equivalent concentrations of phosgene from 4, 28 to 68.5 μg/cm? and contain a constant concentration of the internal standard. For each series, five parallel measurements are carried out on a chromatograph of the LHM-8MD type using a flame ionization detector and a differential gas supply system. Conditions for gas chromatographic determination: steel column (Zmkhaimm), solid carrier Ipepop Zyreg (0.125-0.160mm), stationary phase OM-1 - 595, column temperature 1907С, evaporated temperature 250 "С, carrier gas velocity O.Bcm3/s, hydrogen velocity 0.8cm3/s , air speed 4.Bcm/s, volume of sample to be analyzed μl. After registering the chromatograms, the ratio of the peak heights of phosgene and phenanthrene is calculated. The calibration characteristic reflects the dependence of the ratio of the peak heights of phosgene and the internal standard on the ratio of the concentrations of the corresponding substances. The calibration characteristic equation is linear in the specified concentration range. with

Example 1. Quantitative determination of phosgene in a gas sample (he sample)

A gas-air mixture with a volumetric flow rate of 0.2 dm C/min is passed through. through an absorbent vessel with a porous plate containing 10 cm? a mixture of piperidine and chloroform in a volume ratio of 1:20. The sample volume of the air-gas mixture is 4.75 dm. The contents of the absorption vessel are transferred to a colorimetric test tube with a ground stopper and stored in a dark place. For analysis, 0.9 cm is taken from the sample and added to it

Osm3 of a standard solution of phenanthrene with a concentration of 13 bOmkg/cm?, mixed thoroughly and chromatographed on a chromatograph of the LHM - 8MD type using a flame ionization detector and a differential gas supply system according to the method of the internal standard for which phenanthrene serves. Conditions for gas chromatographic determination: steel column (Zmkhimm), solid carrier Ipepop Zyreg (0.125-0.16Ω), - stationary phase OMU-1 - 595, column temperature 1907"C, evaporator temperature 2507C, carrier gas velocity "U

O, Bcm3/s, hydrogen velocity 0.8cm3/s, air velocity 4.Bcm3/s, sample volume to be analyzed μl.

The ratio of the peak heights of phosgene and phenanthrene is found to be 31.03. According to the equation of the calibration characteristic, the ratio of the equivalent concentration of phosgene and the concentration of phenanthrene (x) is determined and the concentration of phosgene (C) is calculated. shi s S-HOso (2) ;" where Co is the concentration of the internal standard

The concentration of phosgene in the absorption mixture is 15.77 μg/cm.

The mass concentration of phosgene in the gas sample p (SOCI") mg/m3 is determined by the formula (95) -I В(СОСИ2)-СОМобщиМго (3) 1 where C is the concentration of phosgene in the absorbing mixture, μg/cmU; sl 20 Mobsch 7 volume of absorbent mixture of piperidine with chloroform, cm;

M»2o - the volume of the aspirated gas sample brought to standard conditions, dm. sl In the given example, the mass concentration of phosgene is 33.2 mg/m З and the relative mean square deviation of the measurement result is 2.2090.

Example 2. Quantitative determination of phosgene in solution. 59 A model solution of phosgene is prepared as follows. 2.5 cm of a solution (F) of 1,1"-carbonyl(1-piperidyl) with an equivalent concentration of phosgene of 85.7 μg/cm and 2.5 cm of a standard solution of phenanthrene with a concentration of 13 μg/cm are introduced into a measuring vessel. and add 20 cm? phosgene reagent (volume ratio of piperidine to chloroform 1:70). The equivalent concentration of phosgene in the model solution is 608.Bmkg/cm3. The solution is mixed and chromatographed and calculations are carried out according to formulas (2-3) as given in example 1.

The mass concentration of phosgene is found, which is 8.3Bmkg/cm U. The relative error of determination is 2.5790.

Examples 3-8 are similar to example 2, the equivalent mass concentration of phosgene was changed in the model solutions. The data are given in table. 1. b5

Table 1

Example number |Ratio of reagent components, vol. Phosgene introduced, μg/cm3 Phosgene found, μg/m3 Relative error, 95 81000101 vv 55 ni p o o B BD lava 4339 v tla 1603 ju 17111 Bidy 537

Comparative characteristics of the known and declared methods of determining phosgene n:

Stability of samples

The effect of chlorine impurities interferes with concentrations above 2mg/m3

The effect of impurities of halogen anhydrides of carboxylic acids

From the examples given, it is clear that the technical result of the proposed method is high selectivity, with a decrease in the relative error of the determination of phosgene in the sample by two times, and an increase in the shelf life of the sample by 24 times. The proposed method provides the possibility of chromatographic determination of phosgene in gas samples i) and organic solvents. The high selectivity of the method in comparison with the known technical solution makes it possible to determine phosgene in complex gas mixtures with a large number of impurities, which are formed in emergency situations during fires. yu

IF)

Claims (1)

The formula of the invention IF) The method of quantitative determination of phosgene by taking the analyzed sample and treating it with a reagent for phosgene, and - 35, which differs in that a mixture of piperidine and chloroform is used as a reagent for phosgene in a volume ratio of 1:80 to 1 :10, and determine phosgene by gas chromatography using a flame ionization detector using the internal standard of phenanthrene. Official bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated "microcircuits", 2003, M 11, 11/15/2003. State Department of Intellectual Property of the Ministry of Education and Higher Education of Science of Ukraine. . and? (95) and 1 1 sl name) 60 b5