SU1416899A1 - Method of quantitative analysis of methylmercaptan in air - Google Patents

Abstract

The invention relates to analytical chemistry, in particular the quantitative determination of methyl mercaptan in air. The analysis is carried out by absorption of the sample with a solution of mercury acetate, followed by treatment of the obtained solution N, K-dimethyl-p-phenylenediamine in the presence of FeClj and HCl. Then, the colored solution is photometrized and the concentration of mercaptan is determined by a calibration curve constructed using a standard sample. The latter is collected with dimethyl sulfide treated with H, H-dimethyl-p-phenylene diamine in the presence of ethanol. These conditions increase the accuracy of the analysis to 0.2 mg / m when aspirating 5 liters of air. 5 tab. (L

Description

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a well-installed system of two sorption tubes in which 0.5 ml of the absorption solution was applied to an inert carrier (a mixture of four volumes of a 5% aqueous solution of mercury acetate and one volume of glycerin).

The sorption tube is a glass tube with a diameter of 10 mm and a length of 180-200 mm, in which 2-3 ml of glass granules with a diameter of 2-3 mm are placed between two perforated partitions.

At the end of the sampling, 4 ml of the volume was supplied to 6.5 ml with water, 2 MP of ethanol was poured, 0.5 MP of the chromogenic reagent was mixed, and the mixture was measured

1U168992

The invention relates to analytical chemistry, and specifically to methods for the quantitative determination of methyl mercaptan in air.

The purpose of the invention is to improve the accuracy of the method.

Example. The basic solution for establishing the calibration characteristic of the curve is prepared by dissolving Q of an accurate weight of dimethyl disulfide (DVDS) in ethanol in a volumetric flask (about 25 MP). Calculate the content of dimethyl, 1 mp solution,

1 mg of dimethyl disulfide corresponds to 15 swallowing solution is transferred from 0.51 mg of methyl mercaptan (MM). Absorptive device into a test tube.

A working standard pacTEiop dimethyl disulfide with a concentration corresponding to a methyl mercaptan content of 25 MCH / ML is prepared by calculating -20 the optical density as the dilution of the main solution indicated above, with ethanol. When sampling using a sorbent In a series of tubes from a ground solution, the film of the absorption ficke, together with the formed stoppers, are added in 0.5 mp 5% by 25 tons of mercury acetate solution and washed off with 6.5 ml of mercury acetate solution; .If the selection. water. and 2.0 ml of ethanol are introduced into samples and 0.5 ml of the chromogenic reagent is added to liquid samples, absorbing devices, or 0.5 ml are absorbed and the solution is photometric. If the expected concentration of methylmer-porous carrier in the sorption 30 captan in the air is high (e.g., tubes (freshly prepared mixture in industrial emissions, at the source of 5% mercury acetate and glycerin taken in a 4: 1 ratio ), if samples are taken into sorption tubes. Then a working standard solution is added to the tubes in the amount of 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1 , 6; 2.0 ml and the volume was adjusted to 2.5 ml with ethanol. To each tube was poured 6.5 ml of water and 0.5 ml of chromogen-Q reagent - (a mixture of 0.2% of a solution of H, N-dimethyl-p-phenylenediamine hydrochloric acid in concentrated hydrochloric acid and 4% solution of ferric (III) chloride in a 1N solution of hydrochloric acid, taken in a ratio of 3: 1). After 15 min. The optical density of the colored solutions at a wavelength of 500 nm in cuvettes with a layer thickness of 2 cm relative to cont. -50

35

AI), analyze the aliquot part of the washout ..

The concentration of metalmercaptan in the air (s) is calculated by the formula

 (mg / m)

where a is the amount of methyl mercaptan found in VaA analysis

V roll solution. On the basis of the data obtained, the calibration curve equation is calculated.

5 l of the test air is aspirated at a rate of 0.5-1.0 l / min through two successively connected absorption devices containing 5 ml of O, 5% aqueous solution of mercury acetate, or at a speed of 3-5 l / min through verti: 55

Driven solution according to the equation of calibration .., µg;

volume of sample solution, ml; the volume of an aliquot of the sample solution taken for analysis, ml;

volume of air under investigation. ha l

In tab. 1 shows examples of methyl mercaptan detection in air.

In tab. Figure 2 presents data confirming the quantitative nature of the hydrolytic decomposition of dimethyl disulfide to methyl mercaptan in the presence of mercury ions and hydrochloric acid solution of N, N-dimethyl-p-phenylenediamine and ferric chloride. The molecular and mass ratio of DMDS: MM is calculated from experimental data, and

a well-installed system of two sorption tubes in which 0.5 ml of the absorption solution was applied to an inert carrier (a mixture of four volumes of a 5% aqueous solution of mercury acetate and one volume of glycerin).

The sorption tube is a glass tube with a diameter of 10 mm and a length of 180-200 mm, in which 2-3 ml of glass granules with a diameter of 2-3 mm are placed between two perforated partitions.

At the end of the sampling, 4 ml of the volume was supplied to 6.5 ml with water, 2 MP of ethanol was poured, 0.5 MP of the chromogenic reagent was mixed, and the mixture was measured

the swallowing solution is transferred from the absorption device to the tube.

the optical density as described above. When sampling using sorption tubes, the film of the absorption solution together with the methyl mercaptide formed mercury is rinsed off with 6.5 ml. water and 2.0 ml of ethanol, add 0.5 ml of the chromogenic reagent to the tube, mix and photometrize the solution. If the expected concentration of methylmer-30 captan in the air is high (for example, in industrial emissions, at the source in the gap Q

35

AI), analyze the aliquot part of the washout ..

The concentration of metalmercaptan in the air (s) is calculated by the formula

 (mg / m)

where a is the amount of methyl mercaptan found in the analysis tubes the film of the absorption solution together with the mercury methyl mercaptide is washed off with 6.5 ml of water. and 2.0 ml of ethanol are added to the tube with 0.5 ml of the chromogenic reagent, mixed and photometrized solution. If the expected concentration of methyl mercaptan in the air is high (for example, in industrial emissions, at the source of

 o5sch VaA

V

Driven solution according to the equation of calibration .., µg;

volume of sample solution, ml; the volume of an aliquot of the sample solution taken for analysis, ml;

volume of air under investigation. ha l

In tab. 1 shows examples of methyl mercaptan detection in air.

In tab. Figure 2 presents data confirming the quantitative nature of the hydrolytic decomposition of dimethyl disulfide to methyl mercaptan in the presence of mercury ions and hydrochloric acid solution of N, N-dimethyl-p-phenylenediamine and ferric chloride. The molecular and mass ratio of DMDS: MM is calculated from experimental data, and

the theoretical, calculated from molecular weights, is 1: 1 and 1: 0.51, respectively.

In tab. Figures 3 and 4 show the results of the construction of a calibration graph for the determination of methyl mercaptan using dimethyl disulfide and freshly prepared methyl mercaptide lead (by a known method) as a standard sample and their statistical processing.

The data table. 2-4 indicate the possibility of using dimethyl disulfide as a standard substance in the determination of methyl mercaptan.

In tab. 5 presents the results of the determination of methyl mercaptan in the air by the known and proposed method.

From tab. 5, it follows that the use of lead methyl mercaptide standard samples stored in laboratories leads to a large error in measuring the concentrations of methyl mercaptan in the air.

The lower limit for measuring the concentration of methyl mercaptan in solution is 1 µg in the volume to be measured.

The determination of methyl mercaptan by reaction with S, N-dimethyl-p-phenylenediamine and sampling for a sorbent containing mercury acetate does not interfere with acetaldehyde, formaldehyde, acrolein.

methanol, methyl mercaptopropionic aldehyde, phenols, turpentine, carbonic acids, dimethyl sulfide, hydrogen sulfide (up to 50 μg) and sulfur dioxide (up to 200 μg). Dimethyl disulfide does not interfere with the determination only in the case of the use of sorption tubes and the rate of aspiration of the test air above 3 l / min.

The sensitivity of measuring the concentration of mercaptan in air is determined by the volume of air sampled for analysis, which depends on the object and purpose of the analysis.

In the determination of methyl mercaptan in the air of the working area at the level of the maximum permissible concentration (0.8 mg / m), it is sufficient to select 5 to 20 liters of air. Detection sensitivity of 0.2 mg / m when aspirating 5 liters of air.

Mule Invention

20 F o r

A method for the quantitative determination of methyl mercaptan in air by absorbing it with a solution of mercury acetate,

25 treatment of the resulting solution with N, N-dimethyl-p-phenylenediamine in the presence of iron (III) chloride and hydrochloric acid, followed by photometry of the colored solution and determination of the concentration of methyl mercaptan according to a calibration curve, which is based on In order to improve the accuracy of the method, Dimethyl disulfide is used as a standard sample and N, N-dimethyl-p-phenylenediamine treatment is carried out in the presence of ethanol.

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Table 2

The ratio of the optical density of colored solutions, depending on the content of dimethyl disulfide and methyl mercaptan

... The average

.1: 1 1.96: 1

(1: 0.51)

Table3

Dependence of the optical density of calibration solutions prepared using dimethyl disulfide and methyl mercactide lead ()

from methylcaptan content

Dimethyl-

sulfide0.019 0.038 0.092 0.181 0.362 0.542 0.732 0.912

Methyl mercaptide lead 0.020 0.038 0.092 0.183 0.368 0.543 0.730 0.915

9141689910

T ablitsa

Statistical data of results of OPE (methyl mercaptan solids in solution of pax dimethyl disulfide and methyl mercaptide lead ()

Found mercaptan, mg / m, according to the method

Claims (2)

20 Formula of the invention A method for the quantitative determination of methyl mercaptan in air by absorbing it with a solution of mercury acetate, 25 processing the resulting solution of Ν, Ν dimethyl-p-phenylenediamine in the presence of iron (III) chloride and hydrochloric acid, followed by photometric measurement of the colored solution and determining the concentration of methyl mercaptan according to the calibration graph constructed according to a standard sample, characterized in that, in order to increase the accuracy of the method, dimethyldisulfide and a process are used as a standard sample heel Ν, Νdimetil-p-phenylene diamine is carried out in the presence of ethanol. 1.1 + 0.27 4.95 + 0.72 19.9 + 1.15 40.3 + 0.97 0.1 0.05 0.1 0.3 Dimethyldisulfide (4 samples) 5,0 4.76. 0.160 4.76 + 1.1 0.24 20,0 0,062 19.5 + 1.92 0.55 Methyl mercaptide (4 samples) 5,0 4.14 0.221 4.14 + 1.47 0.86 20,0 17.40 0,112 17,413,1 1.10 4.95 19.90 40.30 0.150 0,091 0,036 0.015 1,0 5,0 20,0 60.0 1: 1 1.96: 1 (1: 0.51) TABLE 3 Dependence of the optical density of calibration solutions prepared using dimethyldisulphide and lead methyl mercaptide (n = 10) on the content of methylcaptan in them Standard sample 1,0 | 2.0 The content of methyl mercaptan, mcg 5,0 10.0 | 20,0 | oh oh 40,0 50,0 Dimethyl sulfide 0.019 0,038 0,092 0.181 0.362 0.542 0.732 0.912 Lead methyl mercaptide 0,020 ' 0,038 0,092 0.183 0.368 0.543 0.730 0.915 Table4 Statistical data on the results of determination of methyl mercaptan in solutions of dimethyl disulfide and lead methyl mercaptide (n = 5) (1 sample) 4.9 + 0.74 4.90 5,0 0.1 0,995 20,0 20.05 0,035 20.0511.13 0.05 40,0 39.90 0.014 39 ·, 9 + 0.89 0.1 I Methylmer: lead captide (1 freshly prepared sample) 1 1 nJ *1 from# TO X φ about. to nJ X b and b Ε ". in. f I f X nJ tn " I TO Ο X X to 0. Yu about φ I in X ha x Examples of determination of methyl mercaptan in air G - '............ ----------- 1 1 X in ι ι s. x ha ι o in ha x 1 H d r. about. | in about F 1 O F y X I B V X  i 1 s a x 1 ha in E-g Φ 1 1 1 about  x in 1 b>. in M 1 f X cp and u Oh! ho ha ha ha ha in loxraoraaxx Φ ·> 1 Х Х И ВО ВО Х га and ha ι o >> f f- S ha · θ> "X 1 -9 a, 4 and S o ha ha ha 1. hyu ha o s yy m to Ί gaooavvhv σ> JV | SCH about mien r- <r i— CO * * - l Η * "to "4 * 44, 44 1 * 44 4t eleven" Joint venture - | tn 00 - [σ> YU oio about in oiun ν— I-- 1-- tn l <t | t ~ - IN W AND I1 T— about o · CO 00 CO about' * 9" 44 A 44 "4 44 4" r— CO \ O about tn about T- CM co 00 co g *. about about cm with about Τ- CM CM about 00 about w σι about Ο co about with about about about about *1 44 44 a "4 "4 "4 44 44 about about about ABOUT ABOUT ABOUT about ABOUT ABOUT 44 nJ nJ in a about " X ha 3 f in n > 0 and " Yu nJ Joint venture about a X 1 1 (0 ABOUT Λ go ha 3 about IN go and about *5 nJ a S a in go X nJ about f a 3rd 1 s about about a ha in in X * nJ F nJ a. fl X 1 o yu s 1st ' about " 1 in ABOUT ABOUT tn UO about Yu Yu about tn "L 44 .44 44 to 44 44 44 44 44 44 <? 00 00 00 00 cn 00 00 about about w w hl Yu tn CPU GL 1L 44 44 44 44 44 44 44 4" 44 44 w tn With 00 00 00 00 00 00 00 - cm G i 1 _m 1 4) az f Ts a 3 F o in in <o in X x nJ about in a a S about in f in in in go in f X a about s 3 ABOUT and S RC about ABOUT about ABOUT 44 44 44 * about About cm cm • 1416899 Table 2 The ratio of the optical density of the colored solutions, depending on the content of dimethyldisulfide and methyl mercaptan ----------------- ^- Methyl mercaptan Dimethyl sulfide Methyl mercaptan found in DIDS hydrolysis The ratio of the amounts of DIDS and methyl mercaptan formed during the hydrolysis of DIDS, DIDS: MM Taken, mcg Optical density Taken Optical density ICG M-10 ⁸ mcg Μ · 10 ^β molar j / mass 5 0,092 5 5.3 0,048 2.6 5,4 0.98: 1 1.92: 1 10 0.183 10 10.6 0,093 5.08 10.6 1: 1 1.96: 1 20 0.366 20 21.6 0.190 10.38 21.6 1: 0.98 93: 1 40 0.732 40 42.5 0.375 20.63 42.9 0.99: 1 1.94: 1 fifty 0.915 fifty 53.1 0.465 25.41 52.8 1: 1 1.97: 1 60 1,098 60 63.7 0.560 30.61 63.6 1: 1 1.96: 1 80 84.9 0.720 39.34 81.9 1.03: 1 2.03: 1 100 106,2 0.910 49.73 102.3 1.03: 1 2.00: 1 . Average 2.6 T. table 5 The results of determining the content of methyl mercaptan according to the known and proposed methods Found mercaptan, mg / m ³ according to the method offer- mom famous Stand. sample 1 (freshly prepared) Stand. sample 2 Stand. sample 3 1.10 1.10 1.40 1,60 3.25 3.25 4.00 4,50 7.55 7.55 9.36 10.70 VNIIIPI Order 4060/42 Circulation 847 Subscription Custom polygr. ave, city of Uzhhorod, st. Project, 4