RU2747964C1 - Gas chromatographic method for quantitative determination of chloroacetophenone in air by internal standard method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of quantitative gas chromatographic analysis of chloroacetophenone in air by the internal standard method relates to the field of gas chromatographic analysis of halogenated aromatic ketones. The essence of the method consists in the quantitative analysis on a gas chromatograph with a flame ionization detector of air samples containing chloroacetophenone taken for an absorption solution, namely isopropyl alcohol, in an absorption device with a porous glass plate, and calculating its mass concentration using the relative calibration coefficient for the internal the standard in which diphenyl is used.

EFFECT: invention is aimed at effectiveness of isopropyl alcohol, providing a high degree of absorption of chloroacetophenone from the air, and its low hazard (hazard class 3), no need for a state standard sample or chemically pure chloroacetophenone for calibration of the device.

1 cl, 3 dwg, 4 tbl

Description

The invention relates to the field of gas chromatographic analysis of halogenated aromatic ketones.

The literature describes a method for measuring the mass concentration of chloroacetophenone (CAF) in the air of the working area by the gas chromatographic method on a device with an electron capture detector [1]. In accordance with this method, the determination of the content of chloroacetophenone in the air of the working area is performed by gas chromatography by:

- capturing chloroacetophenone from atmospheric air into isobutyl alcohol;

- measurements of the mass concentration of chloroacetophenone in solution according to a calibration graph on a chromatograph equipped with an electron capture detector (ECD) and a HP-INNOWax quartz capillary column with a chemically grafted Polyethylene Glycol liquid stationary phase.

The disadvantage of this method is the need for preliminary calibration of the chromatograph, which requires the presence of chemically pure chloroacetophenone, which belongs to the group of physiologically active irritant substances. In addition, a relatively small number of gas chromatographs are equipped with electron capture detectors.

The purpose of the present invention is to provide a method for the quantitative gas chromatographic analysis of chloroacetophenone in air, which does not require the mandatory presence of a sample of a chemically pure substance, using a universal and widespread flame ionization detector.

The objectives of the present invention are to select:

- absorption solution for chloroacetophenone (low-toxic and inexpensive);

- conditions of sample preparation and sampling;

- optimal conditions for gas chromatographic determination of the concentration of chloroacetophenone;

- internal standard and determination of the relative calibration factor.

The essence of the method consists in the quantitative analysis on a gas chromatograph with a flame ionization detector of air samples containing chloroacetophenone, taken for an absorption solution (isopropyl alcohol) in an absorption device with a porous glass plate, and the calculation of its mass concentration using the relative calibration coefficient according to the internal standard, which is used as diphenyl.

The technical result achieved in the claimed invention consists in:

- exclusion of multistage;

- simplification of sample preparation;

- the effectiveness of isopropyl alcohol, providing a high degree of absorption of chloroacetophenone from the air, and its low hazard (hazard class 3);

- no need for a state standard sample or chemically pure chloroacetophenone to calibrate the device;

- the simplicity of the calculations.

The specified technical result is achieved by:

- the conditions for air sampling were determined;

- the optimal conditions for gas chromatographic analysis were established, which ensure the reliability of quantitative results;

- an internal standard was selected for the quantitative determination of chloroacetophenone in air, for which the possibility of using dodecane, biphenyl, n-chlorobiphenyl and methyl palmitate in this capacity was checked;

- the device was calibrated and the calibration dependencies were built;

- the relative calibration coefficient is calculated, the reliability of its value is shown.

Among the substances included in the standard composition for the calibration of a gas chromatograph, diphenyl meets all the requirements for internal standards, therefore, it can be selected as an internal standard for the quantitative determination of CAF. The main properties of biphenyl and CAF are presented in Table 1.

The gas chromatograph was calibrated by the internal standard method, which was diphenyl. Calibration solutions were prepared containing chloroacetophenone and diphenyl in isopropyl alcohol by the method of successive dilutions. ^{A 2 mm 3} sample of calibration solutions with a concentration from 10 ^-1 to 5⋅10 ³ μg / cm ³ was introduced into the chromatograph, each of the solutions at least 6 times.

Using the standard ChemStation program for collecting and processing chromatographic information, the area of the CAF peak with a retention time of 8.7 (± 0.4) minutes and biphenyl with a retention time of 9.7 (± 0.3) were measured on the chromatogram. The measurements were carried out with the following operating parameters of the chromatograph [3]:

- the temperature of the column thermostat is 40 ° С, the plateau is 1 minute;

- heating rate - 15 ° С / min up to 260 ° С;

- evaporator temperature 230 ° С;

- split ratio 20: 1;

- detector temperature 270 ° С;

- the flow rate of the carrier gas 1.0 cm ³ / min;

- air flow rate 300 cm ³ / min;

- hydrogen flow rate 30 cm / min;

- capillary column HP-5MS 30 m D-0.32 mm F-0.25 μm;

- sample volume 2 mm ³ .

Under these conditions, chromatograms of solutions of chloroacetophenone and biphenyl in isopropyl alcohol were obtained on an Agilent 6890N gas chromatograph with a flame ionization detector (Figure 1).

Based on the measurement data presented in Tables 1 and 2, the calibration dependences of chloroacetophenone and biphenyl for concentrations from 10 ^-1 to 5 310 ³ μg / cm ^{3 were} constructed (Figures 2 and 3, respectively).

Based on the values of the peak areas of chloroacetophenone and biphenyl, the value of the relative calibration coefficient for each concentration was calculated using the formula:

where C _HAF , C _ST - mass concentrations of chloroacetophenone and internal standard (biphenyl), μg / cm ³ ;

S _HAF , S _ST - corresponding peak areas of chloroacetophenone and internal standard (biphenyl), rel. units

Then the obtained values were processed mathematically. The calculation results are presented in Table 3.

From the data presented in table 3, it can be seen that the calculated value of the relative calibration coefficient has a value of 1.72 with a relative error of 1.0% for all tested concentrations of chloroacetophenone and biphenyl.

To determine the concentration of chloroacetophenone in the air, an absorber with a porous plate is weighed on an analytical balance, and 2 ml of isopropyl alcohol is added with a dispenser. During sampling, record the atmospheric pressure and temperature at the sampling point. The absorber is connected to the outlet of the aspirator and the analyzed air is aspirated through the absorber at a rate of 0.5 dm ³ / min for 10 min. The absorber is disconnected and reweighed. The mass of the absorption solution is determined from the difference in weights. The total volume of passed air is 5.0 dm ³ . Then 1 cm ^{3 of the} absorption solution is transferred into a vial with a capacity of 2.0 cm ³ , to which 1 cm ^{3 of a} solution of biphenyl with a concentration of 100 μg / cm ³ is added and a quantitative gas chromatographic analysis is carried out under the conditions indicated above.

Into the chromatograph using a microsyringe, inject 2 mm ^{3 of the} combined air and witness sample and record the peak area of chloroacetophenone HAF with a retention time of 8.7 (± 0.4) minutes and biphenyl with a retention time of 9.7 (± 0.3). When analyzing an air sample, at least two parallel determinations are performed.

Calculate the content of chloroacetophenone in the analyzed solution (C _p , μg / cm ³ ) according to the formula:

where ƒ _HAF is the relative calibration coefficient of chloroacetophenone according to the internal standard (biphenyl), equal to 1.72;

C _ST - mass concentration of the internal standard (biphenyl), μg / cm ³ ;

S _HAF , S _ST - peak areas of chloroacetophenone and internal standard (biphenyl), rel. units

The mass concentration of CAF in the air sample C, mg / dm ³ , is calculated by the formula:

where C _p is the mass concentration of CAF in the solution, found by the formula (2), μg / cm ³ ;

m ₁ is the mass of the empty absorber, g;

m ₂ is the mass of the absorber with isobutyl alcohol after air sampling, g;

ρ is the specific gravity of isopropyl alcohol (ρ = 0.785), g / cm ³ ;

K is the coefficient of substance loss (K = 0.90);

V ₀ - volume of the sampled air, l, reduced to n.o. (V ₀ ≈ 5.0 dm ³ );

1000 - conversion factor μg to mg.

In accordance with GOST 8.395, at a temperature of 293 K (20 ° C) and atmospheric pressure of 101.3 kPa (760 mm Hg), the volume of the sampled air is brought to normal conditions using the following formula:

where d _in is the volumetric flow rate of air passed through the absorbing device, dm ³ / min (d _in = 0.5 dm ³ / min);

τ is the sampling time, min (10 min);

Р - atmospheric pressure, kPa;

t - ambient temperature during sampling, ° С.

The arithmetic mean of two parallel definitions is taken as the result.

Information sources

1. FR.1.31.2015.21511. Technique (method) for measuring the mass concentration of chloroacetophenone in the air of the working area by gas chromatography using an electron capture detector. - Certificate of Attestation No. 310003.08 / 33-2015 dated 06/30/2015.

2. Handbook of a chemist. Volume II. Basic properties of inorganic and organic compounds / Ed. 3rd rev. // Ed. B.P. Nikolsky. - L .: Publishing house "Chemistry", Leningrad branch, 1971. - 1168 p.

3. Resolution of the Chief State Sanitary Doctor of the Russian Federation of December 22, 2017 N 165 "On approval of hygienic standards GN 2.1.6.3492-17" Maximum permissible concentrations (MPC) of pollutants in the air of urban and rural settlements "(together with" GN 2.1.6.3492 -17. Hygienic standards ... ") (Registered in the Ministry of Justice of Russia 09.01.2018 N 49557) [Electronic resource]. - URL: http://www.consultant.ru.

4. Resolution of the Chief State Sanitary Doctor of the Russian Federation of 13.02.2018 N 25 On the approval of hygienic standards GN 2.2.5.3532-18 "Maximum permissible concentrations (MPC) of harmful substances in the air of the working area" (Registered in the Ministry of Justice of Russia on 20.04.2018 N 50845) [ Electronic resource]. - URL: http://www.consultant.ru.

Claims (1)

Gas chromatographic method for the quantitative determination of chloroacetophenone in air, characterized in that air samples taken for an absorption solution, namely isopropyl alcohol, are analyzed on a gas chromatograph with a flame ionization detector, the concentration of chloroacetophenone is calculated by the method of an internal standard, which is used as diphenyl.

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