Method for determining pentachloroethane in workplace

Abstract

The invention relates to a method for determining pentachloroethane in a workplace, which comprises the following steps: sampling at a sampling point: sampling for a short time, sampling for a long time and blank sampling, immediately closing two ends of an activated carbon tube after sampling, and transporting and storing in a clean container; sample treatment and determination: respectively pouring the front and rear sections of activated carbon in the activated carbon tube into a solvent desorption bottle, adding benzene-free carbon disulfide, sealing, desorbing, and shaking from time to time, so as to obtain a sample solution for determination; drawing a standard curve: dissolving pentachloroethane in benzene-free carbon disulfide, quantitatively transferring into a 10ml volumetric flask, adding a desorption solution to a scale to serve as a standard stock solution, and gradually diluting into a standard series; and then adjusting the gas chromatograph according to instrument operation conditions, determining each standard series, and drawing a standard curve for the concentration of pentachloroethane according to a measured peak area value. The method adopts the gas chromatography for determination, has the advantages of high sensitivity, good selectivity, high analysis speed and the like, and can meet the determination requirements of pentachloroethane in workstations.

Description

Technical Field

[0001] The invention belongs to the technical field of pentachloroethane detection, in particular to a method for determining pentachloroethane in a workplace. Background Art

[0002] Pentachloroethane, chemical formula C2HCl5, is a colorless liquid, insoluble in water, miscible in ethanol, ether and common organic solvents. It is a good polar solvent, detergent, ore flotation agent, wood drying agent, and is also used to make tetrachloroethylene (anthelmintic), hexachloroethane (veterinary anthelmintic), etc. It is also a by-product of the production of hexachloroethane by the ethylene chlorination method and the ethane chlorination method.

[0003] But at the same time, pentachloroethane also has a certain anesthetic effect, irritates the eyes and upper respiratory tract, and may cause liver and kidney damage. In October 2017, the World Health Organization's International Agency for Research on Cancer published a preliminary list of carcinogens for reference, and pentachloroethane is on the list of Class 3 carcinogens. Therefore, accurately measuring the content of pentachloroethane in the air of the workplace is crucial to protecting the health of workers.

[0004] However, there is no method for detecting the content of pentachloroethane in the air of workplaces in my country at present. Therefore, there is an urgent need for a method for determining pentachloroethane in workplaces that is simple to operate and highly accurate. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for determining pentachloroethane in a workplace which has the advantages of simple operation, high accuracy and low detection limit.

[0006] The present invention solves the technical problem by adopting the following technical solutions:

[0007] A method for determining pentachloroethane in a workplace comprises the following steps:

[0008] S1. Sampling at sampling point: Immediately seal both ends of the activated carbon tube after sampling and place it in a clean container for transportation and storage;

[0009] S2. Sample processing and determination: pour the front and rear activated carbon in the activated carbon tube into the solvent desorption bottle respectively, add benzene-free carbon disulfide, seal, desorb, shake from time to time, and the sample solution is ready for determination;

[0010] S3. Drawing of standard curve: dissolve pentachloroethane in benzene-free carbon disulfide, transfer quantitatively to a 10 ml volumetric flask, add desorption liquid to the scale, use as standard stock solution, and dilute step by step into standard series; then adjust the gas chromatograph according to the instrument operating conditions, measure each standard series, and draw a standard curve based on the measured peak area value versus pentachloroethane concentration;

[0011] The gas chromatograph conditions were as follows: the temperature program was 60°C for 8 min, then increased to 140°C at a rate of 10°C / min and maintained for 8 min; the inlet temperature was 250°C, the carrier gas flow rate was 1.00 mL / min, the split ratio was 5:1, and the detector temperature was 250°C.

[0012] Moreover, the short-time sampling is to collect air samples for 15-30 minutes at a flow rate of 100-300mL / min using an activated carbon tube at the sampling point, the long-time sampling is to collect air samples for 2-8 hours at a flow rate of 20-50mL / min using an activated carbon tube at the sampling point, and the blank sampling is to collect air samples without connecting the air sampling device.

[0013] Moreover, the sample can be stored at room temperature for 7 days.

[0014] Moreover, the sampling medium is a solvent desorption type activated carbon tube.

[0015] Furthermore, the gas chromatograph uses a CP-WAX58 FFAP capillary column of 30 m×0.32 mm×1.00 μm.

[0016] Furthermore, the benzene-free carbon disulfide in step S2 contains 0.1% of trifluoroacetic acid.

[0017] The advantages and positive effects of the present invention are:

[0018] 1. The present invention adopts suitable sampling media and pretreatment methods, which can effectively improve the sample recovery rate and the accuracy of the measurement. The measurement method of the present invention is simple to operate, does not require complex instruments and professional technicians, and is suitable for on-site measurement in various workplaces.

[0019] 2. Pentachloroethane has certain toxicity and danger. Accurate determination of its concentration can provide important basis for safe production. The present invention adopts gas chromatography for determination, which has the advantages of high sensitivity, good selectivity, fast analysis speed, etc., and can meet the determination requirements of pentachloroethane in workstations.

[0020] 3. The present invention can provide a scientific basis for environmental management of the workplace and health protection of workers through analysis of the measurement results. Enterprises can formulate reasonable safety operating procedures based on the measurement results, strengthen the management and control of pentachloroethane, prevent accidents, and ensure safe production.

[0021] 4. The present invention uses activated carbon tube sampling, FFAP capillary column separation after carbon disulfide desorption, and gas chromatography with FID detector to determine pentachloroethane in workplace air. The method has high sensitivity and good precision, and is suitable for the determination of pentachloroethane concentration in workplace air. It also provides a reference basis for the simultaneous detection of multiple halogenated hydrocarbons in the workshop air of chemical enterprises, which has positive significance for protecting the health of workers. The stationary phase of the Agilent J&W CP-Wax 58FFAP CB chromatographic column is a chemically bonded polyethylene glycol modified with nitroterephthalic acid. The chromatographic column is specially designed for the analysis of acidic compounds such as phenol, derivatized or underivatized free fatty acids.

[0022] 5. The benzene-free carbon disulfide in step S2 of the present invention contains 0.1% trifluoroacetic acid, which can increase the retention time interval between peaks 15 and 16 and improve the detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the separation spectrum of substances coexisting with pentachloroethane when the CP-WAX58 FFAP chromatographic column is used in the present invention.

[0024] Figure 2 This is the separation spectrum of substances coexisting with pentachloroethane when the DB-1 chromatographic column is used in the present invention.

[0025] Figure 3 This is the separation spectrum of substances coexisting with pentachloroethane when the DB-624 chromatographic column is used in the present invention.

[0026] Figure 4 This is the separation spectrum of substances coexisting with pentachloroethane when the DB-1701 chromatographic column is used in the present invention.

[0027] Figure 5 This is the separation spectrum of substances coexisting with pentachloroethane when the HP-FFAP chromatographic column is used in the present invention.

[0028] Figure 6 This is a standard curve of peak area value versus pentachloroethane concentration when the HP-FFAP chromatographic column is used in the present invention, wherein 1, 2, 3, 4, and 5 respectively represent concentration points (61.25, 123.5, 247.0, 493.9, and 987.8 μg / mL) prepared by the HP-FFAP chromatographic column curve.

[0029] Figure 7 This is a standard curve of peak area value versus pentachloroethane concentration when the CP-WAX58 FFAP chromatographic column is used in the present invention, in which 1, 2, 3, 4, and 5 respectively represent the concentration points (39.90, 79.80, 159.6, 319.2, and 638.4 μg / mL) prepared by the CP-WAX58 FFAP curve.

[0030] Reference numerals

[0031] 1—Solvent peak; 2—Acetone; 3—1,2-Dichloroethylene; 4—1,1,1-Trichloroethane; 5—Benzene; 6—Trichloroethylene; 7—Tetrachloroethylene; 8—Toluene; 9—Ethylbenzene; 10—P-Xylene; 11—M-Xylene; 12—Chlorobenzene; 13—O-Xylene; 14—1,1,2-Trichloroethane; 15—1,1,2,2-Tetrachloroethane; 16—Pentachloroethane; 17—1,2,3-Trichloropropane; 18—Benzyl chloride. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0033] Example 1

[0034] A method for determining pentachloroethane in a workplace. This embodiment is the selection of a chromatographic column and analytical conditions:

[0035] 1. Interference experiment: Benzene, toluene, p-xylene, m-xylene, o-xylene, chlorobenzene, acetone, trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, 1,2,3-trichloropropane, benzyl chloride, etc., which may coexist with pentachloroethane in the workplace air, were selected for interference experiment using five different chromatographic columns: DB-1, DB-624, DB-1701, HP-FFAP and CP-WAX58 FFAP.

[0036] The results show that the presence of all the above substances in pentachloroethane does not affect the determination of pentachloroethane. According to the physical and chemical properties of pentachloroethane, refer to Figure 1-Figure 5 As shown, it was found that the above-mentioned chromatographic columns can separate the analytes well, but in the interference experiment, only the HP-FFAP and CP-WAX58 FFAP columns meet the separation conditions.

[0037] 2. The best chromatographic column was determined by preparing a standard curve, and a curve was plotted based on the measured peak area versus concentration. The regression equation was calculated as follows: Y = 0.3895x + 0.2118, with a correlation coefficient of R = 0.9998 (chromatographic column CP-WAX58 FFAP); Y = 0.1406x - 1.33810, with a correlation coefficient of R = 0.9998 (chromatographic column HP-FFAP).

[0038] It was found that the sensitivity of the CP-WAX58 FFAP column was higher than that of HP-FFAP, so this column CP-WAX58FFAP (30m×0.320mm×1.00μm) was selected as the separation column.

[0039] The detection instrument used in the present invention is a 7890A gas chromatograph produced by Agilent, and experiments are carried out under different conditions for column temperature, injection port temperature, detector temperature, and split ratio to determine the following chromatographic analysis conditions: column temperature is maintained at 60°C for 8.0 min, heated to 140°C at 10°C / min, maintained for 8.0 min, injection port temperature is 250°C, detector temperature is 250°C, carrier gas (N2) flow rate is 1.0 ml / min, split ratio is 5:1, and FID detector is used.

[0040] The filler of the chromatographic column used in this example was manufactured by Agilent.

[0041] Example 2

[0042] A method for determining pentachloroethane in a workplace comprises the following steps:

[0043] S1. Sampling at sampling points: Four different sampling points in one of the chemical laboratories of a certain factory were selected for on-site sampling. The sampling was carried out at a sampling flow rate of 0.3L / min for 15 minutes. After sampling, both ends of the activated carbon tube were immediately sealed and placed in a clean container for transportation and storage. At the same time, blank samples were collected.

[0044] S2. Sample processing and determination: Pour the front and rear activated carbon in the activated carbon tube into the solvent desorption bottle respectively, add 1.0 ml of benzene-free carbon disulfide, seal, desorb for 30 minutes, shake occasionally, and the sample solution is ready for determination.

[0045] S3, standard curve drawing: accurately weigh 0.0420g pentachloroethane, dissolve it in benzene-free carbon disulfide, quantitatively transfer it into a 10ml volumetric flask, add desorption liquid to the scale, this solution is 4200μg / ml pentachloroethane standard solution. Take another 10ml volumetric flask, add 0.0, 0.02, 0.05, 0.10, 0.20, 0.40, 0.80ml of this standard solution respectively, dilute it to the scale with desorption liquid, and prepare a standard series with concentrations of 0.0, 8.40, 21.00, 42.00, 84.00, 168.0 and 336.0μg / ml. Referring to the instrument operating conditions described in Example 1, adjust the gas chromatograph to the optimal state, measure each standard series, and draw a standard curve to measure the peak area value against the pentachloroethane concentration (μg / ml).

[0046] Prepare a pentachloroethane concentration close to the blank solution (8.4 μg / ml) and repeat the measurement 10 times, and calculate the detection limit and quantitative lower limit according to the detection limit calculation formula. The calculation formula is as follows:

[0047]

[0048] Where: C represents the concentration of pentachloroethane in the air, mg / m 3 ; c represents the concentration of pentachloroethane in the sample solution, μg / ml; v represents the volume of the sample solution, ml; D represents the desorption efficiency, %; V0 represents the standard sampling volume, L.

[0049] The detection limit of this method is 1.8μg / ml, the lower limit of quantification is 5.9μg / ml, and the minimum detection concentration is 0.4mg / m 3 The minimum quantitative concentration is 1.3 mg / m 3 The results showed that pentachloroethane was not detected at three of the four sampling points, and the concentration at the remaining sampling point was 6.50 g / ml. The concentration of pentachloroethane in the air at this sampling point was 1.44 mg / m 3 .

[0050] Example 3

[0051] A method for determining pentachloroethane in a workplace, this embodiment is a desorption efficiency test, comprising:

[0052] Prepare a pentachloroethane stock solution with a concentration of 67.2 mg / ml, take 18 activated carbon tubes, divide them into 3 groups, 6 in each group, add 1.0, 2.0 and 4.0 μL of stock solution respectively, put on plastic caps immediately and leave overnight, add 1.0 ml of desorption solution the next day, repeat the measurement 3 times for each concentration, and make a blank of solid adsorbent tube at the same time. The results are shown in Table 1.

[0053] Table 1 Pentachloroethane desorption efficiency test data

[0054]

[0055] Example 4

[0056] A method for determining pentachloroethane in a workplace, this embodiment is an accuracy test, comprising:

[0057] The spike recovery method was used to accurately prepare a 1680μg / ml pentachloroethane stock solution. 24 activated carbon tubes were taken, and 8.0μl of this stock solution was added to each tube to make a uniform sample, which was then divided into 4 groups, with 6 tubes in each group. One group was the sample background, and the other three groups were added with 33.60μg, 134.4μg, and 268.8μg of pentachloroethane (addition method: 1.0, 4.0, and 8.0μL of 33.60mg / ml pentachloroethane solution were added with a micro-syringe, respectively), and the pentachloroethane content was determined. According to statistics, the average recovery rate of pentachloroethane was 98.7%, see Table 2.

[0058] Table 2 Pentachloroethane accuracy test data

[0059]

[0060] Example 5

[0061] A method for determining pentachloroethane in a workplace, this embodiment is a stability test, comprising:

[0062] 50.40μg of pentachloroethane was added to 30 activated carbon tubes and stored at room temperature. Six tubes were taken for measurement on the 1st, 3rd, 5th and 7th days respectively. The results showed that the decrease rates of pentachloroethane on the 1st, 3rd, 5th and 7th days were 0.4%, 3.3%, 6.6% and 9.7% respectively. The decrease rate on the 7th day was less than 10%. Therefore, the pentachloroethane collected by the activated carbon tube in the workplace air can be stored for at least 7 days.

[0063] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for determining pentachloroethane in a workplace, characterized in that: The steps include: S1. Sampling at sampling point: Immediately seal both ends of the activated carbon tube after sampling and place it in a clean container for transportation and storage; S2. Sample processing and determination: pour the front and rear activated carbon in the activated carbon tube into the solvent desorption bottle respectively, add benzene-free carbon disulfide, seal, desorb, shake from time to time, and the sample solution is ready for determination; S3. Drawing of standard curve: dissolve pentachloroethane in benzene-free carbon disulfide, transfer quantitatively to a 10 ml volumetric flask, add desorption liquid to the scale, use as standard stock solution, and dilute step by step into standard series; then adjust the gas chromatograph according to the instrument operating conditions, measure each standard series, and draw a standard curve based on the measured peak area value versus pentachloroethane concentration; The gas chromatograph conditions were as follows: the temperature program was 60°C for 8 min, then increased to 140°C at a rate of 10°C / min and maintained for 8 min; the inlet temperature was 250°C, the carrier gas flow rate was 1.00 mL / min, the split ratio was 5:1, and the detector temperature was 250°C.

2. The method for determining pentachloroethane in a workplace according to claim 1, characterized in that: The short-time sampling is to collect air samples for 15-30 minutes at a flow rate of 100-300mL / min using an activated carbon tube at the sampling point, the long-time sampling is to collect air samples for 2-8 hours at a flow rate of 20-50mL / min using an activated carbon tube at the sampling point, and the blank sampling is to collect air samples without connecting the air sampling device.

3. The method for determining pentachloroethane in a workplace according to claim 2, characterized in that: The sample can be stored at room temperature for 7 days.

4. The method for determining pentachloroethane in a workplace according to claim 3, characterized in that: The sampling medium is a solvent desorption type activated carbon tube.

5. The method for determining pentachloroethane in a workplace according to claim 4, characterized in that: The gas chromatograph uses a CP-WAX58 FFAP capillary column of 30m×0.32mm×1.00μm.

6. The method for determining pentachloroethane in a workplace according to claim 5, characterized in that: The benzene-free carbon disulfide in step S2 contains 0.1% of trifluoroacetic acid.

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