Determination of Diacetone Alcohol in the Air of Workshop by Gas Chromatography
Abstract: Diacetone alcohol has an irritating effect on eyes, skin and mucous membranes. Inhalation and ingestion can affect the nervous system and damage the liver and stomach. Inhalation of high concentrations can cause pulmonary edema and even coma. Long-term exposure can cause dermatitis.
A method for collecting diacetone alcohol in the air with activated carbon, desorption by 1.5% isoamyl alcohol disulfide solution, separation by FFAP column, and detection by hydrogen flame ionization detector, relative standard deviation of 4.3% to 8.0%, desorption efficiency It is 86.8%, the penetration capacity is greater than 11.5mg / 100mg activated carbon, the detection limit is 5.7 × 10-3μg (injection 1 microliter), the sample can be stored in the activated carbon tube for at least 5 days at room temperature.
Diacetone alcohol (diacetonealcohol) is a flammable liquid with a boiling point of 169.2 ° C. It is formed by condensation of 2 molecules of acetone in the presence of an alkaline substance. Widely used as a solvent for cellulose acetate, paints, dyes, resins, etc., antifreeze and antiseptic for the preparation of pharmaceuticals. Long-term repeated exposure can cause dermatitis. Mucosal irritation can be seen by absorbing high concentration of diacetone alcohol. In severe cases, it can cause anesthesia and liver and kidney damage.
1. Measurement method
1.1 Principle
The diacetone alcohol in the air was collected with an activated carbon tube. The 1.5% isoamyl alcohol disulfide solution was desorbed and injected. The sample was separated by an FFAP column and detected by a hydrogen flame ionization detector to determine the retention time, peak area or peak height.
1.2 Instruments and reagents
1.2.1 Gas chromatograph, FID.
1.2.2 Sampler, 0 ～ 1.5L / min.
1.2.3 Coconut shell activated carbon, 20 ～ 40 mesh, GH-1 type, nitrogen treatment at 350 ℃ for 4 hours before pipe installation, and reserve after cooling.
1.2.4 Activated carbon tube, 14cm long, 4mm inner diameter glass tube. 100mg in the front section and 50mg activated carbon in the rear section, separated by glass wool in the middle, fixed with glass wool at both ends, and sealed for use.
1.2.5 Test tube with stopper, 5ml.
1.2.6 Micro syringe, 1μl, 0.5μl.
1.2.7 Diacetone alcohol, chemically pure, with a content of not less than 98.5% (Beijing Chemical Factory).
1.2.8 Desorption solvent, 1.5% (V / V) isoamyl alcohol disulfide solution.
1.3 Sampling
Open both ends of the sampling tube at the sampling site, connect the 50mg end of the tube to the sampler, and extract 2L of air at a speed of 0.2L / min. After sampling, the ends of the tube are tightly covered with plastic caps and analyzed within 5 days.
1.4 Analysis steps
1.4.1 Chromatographic conditions
Chromatographic column: 2m long and 3mm inner diameter.
Stationary phase: FFAP: chromosorb. W-AW support = 10: 100.
Column temperature: 100 ° C.
Detector temperature: 180 ° C.
Carrier gas (N2) flow rate: 45ml / min.
1.4.2 Standard curve drawing
Take 0.25, 0.5 and 1.0 μl of diacetone alcohol with a microsyringe (1 μl at 0.90 mg at 20 ° C), add to 1 ml of desorption solvent to make up 234, 468, 937 μg / ml of three standard solutions of different concentrations, take 1 μl each For samples, determine the retention time and peak area, and repeat the injection three times for each concentration. Take the average of the peak area and plot the peak area with the diacetone alcohol content to draw a standard curve.
1.4.3 Sample analysis
Pour the sampled activated carbon tube into the test tube with plug before and after, add 1μl of 1.5% isoamyl alcohol disulfide solution, desorb and shake for 1.5 ~ 2h, then take 1μl of the desorption solution for injection, use retention time to characterize, peak Quantitative area.
1.4.4 Controlled test
With sampling, the activated carbon tube is taken to the site, but no air is extracted, and the analysis is carried out according to the sample analysis step as a blank control.
1.4.5 Quantitative
Calculate the concentration of diacetone alcohol in the air as follows.
In the formula: X—the concentration of diacetone alcohol in the air (mg / m3);
C1, C2—respectively the content of diacetone alcohol (μg) in the activated carbon desorption solution before and after the extraction;
V0—Sampling volume under standard conditions (L);
D—Desorption efficiency (%).
2. Experimental results and discussion
2.1 Method precision, linear relationship and detection limit
Using 1.5% isoamyl alcohol disulfide solution, prepare a standard solution of diacetone alcohol with a concentration of 234,468,937 μg / ml, take 1 μl of injection, continuously measure each concentration for 6 days, measure the peak area, observe the linearity, and calculate the relative standard deviation .
2.2 Determination of penetration capacity
Take two large-mouthed reagent bottles, reagent bottle 1 filled with diacetone alcohol, reagent bottle 2 filled with water, using diffusion dynamic gas distribution method to prepare diacetone alcohol gas, using activated carbon tube at a gas recovery rate of 0.2L / min Diacetone alcohol gas. When the concentration of the gas at the rear of the carbon tube reaches 5% of the gas concentration at the front of the carbon tube, it is penetration. As a result of the experiment, the penetration capacity of 100 mg activated carbon to diacetone alcohol was 11.5 mg under humid air conditions and 14.4 mg under dry air conditions.
2.3 Desorption efficiency test
2.3.1 Desorption solvent selection
Foreign materials use 5% isopropanol carbon disulfide solution to desorb the sampled activated carbon, we use 1% isoamyl alcohol, 1.5% isoamyl alcohol, 2.5% isoamyl alcohol, 2.5% acetone, 5% isopropyl alcohol carbon disulfide solution 1ml for desorption.
2.3.2 Desorption efficiency test results
Take 18 activated carbon tubes, divided into 3 groups, 6 in each group, add 234, 468, 937 μg of diacetone alcohol to each group, let stand overnight to make it equilibrate, and then desorb according to the previous method and measure.
2.4 Sample stability test
Take 24 tubes containing 100mg activated carbon, add 468.5μg of diacetone alcohol respectively, and diffuse to equilibrium at room temperature. Analyze 6 tubes on the day, day 2, day 5 and day 7, and compare the results with the measurement results of the day. Observe the stability.
2.5 Sampling efficiency test
Use 100 and 50 mg activated carbon tubes in the two front and back sections, collect 2L of standard gas with a concentration of 162 mg / m3 and 650 mg / m3 at a rate of 0.2 L / min, and determine the content of diacetone alcohol in the activated carbon in the front and back sections according to the law. Results No diacetone alcohol was detected in the activated carbon in the latter stage, indicating that the sampling efficiency in the activated carbon in the preceding stage was 100%.
2.6 Interference test
Diacetone alcohol is formed by condensation of two molecules of acetone in the presence of an alkaline substance, so acetone may coexist at the production site. It is known from the test that under the chromatographic conditions of this method, the chromatographic peak of acetone and the chromatographic peak of diacetone alcohol can be completely separated from the baseline, and the presence of acetone does not interfere with the determination of diacetone alcohol.
2.7 Method verification
This method was verified by the Occupational Disease Control Institute of Xinxiang City, Henan Province. The results are as follows. When the concentration of diacetone alcohol is 234,468,937 μg / ml, the relative standard deviations measured are 5.8%, 2.9%, 3.5% (n = 6) The detection limit is 2.9 × 10-3μg (injection of 1 microliter), and the average desorption efficiency is 84.2%. 468 μg of diacetone alcohol was added to the activated carbon tube and measured on the same day and after storage at room temperature for 5 days. The results showed that the sample was stable for at least 5 days under this condition. Two activated carbon tubes were connected in series to collect diacetone alcohol, and the sampling efficiency of the front tube reached 100%.
3. Summary
In this paper, a gas chromatography method for diacetone alcohol in air is proposed. The detection limit is 5.7 × 10-3μg. When the content is 234 ～ 937μg / ml, the linear relationship is good. The relative standard deviation of the determination is less than 10%. The method is simple and easy. Accurate and reliable, the collected samples can be stable at room temperature for at least 5 days.
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