Probe into the desorption efficiency of the hottes

Discussion on the desorption efficiency of carbon disulfide for VOCs in indoor air

objective to investigate the desorption efficiency of VOCs components in indoor air in carbon disulfide. Methods VOCs in indoor air were adsorbed by coconut shell activated carbon sampling tube, desorbed by carbon disulfide and determined by gas chromatography. Results the desorption efficiency of carbon disulfide for VOCs components ranged from 86.0% to 95.1%. Conclusion the desorption rate can meet the requirements of the laboratory, avoiding the problems of low repeatability and insufficient desorption rate of thermal desorption

[Key words] indoor air VOCs desorption rate carbon disulfide

volatile organic compounds (VOCs) mainly come from urinary aldehyde trees 13 during the decoration process After the test, the board with ester as adhesive, solvent based coating, water-based coating and foamed plastic used in furniture, etc. Through inhalation of steam or skin absorption, it causes damage to human respiratory system, nervous system and blood circulation system, and even has the possibility of cancer [1]. At present, the determination of VOCs in indoor air is carried out by thermal desorption gas chromatography [2]. Due to the problem of insufficient desorption rate, the author conducted a test on it

1. Materials and methods

1.1 instrument

Shimadzu gc-14b gas chromatograph; Hydrogen flame ionization detector (FID); Shimadzu chromatographic workstation; five μ L microinjector

1.2 reagent

carbon disulfide (analytical purity): repeatedly extract with 5% concentrated sulfuric acid formaldehyde solution until it is colorless, wash it with distilled water to neutral, then dry it with anhydrous sodium sulfate, and re distill. Take purified carbon disulfide 1.0 μ L there should be no impurity peak when injecting into the gas chromatograph. The total volatile organic compounds are chromatographic pure

1.3 preparation of mixed standard stock solution

20 ℃, the mass of benzene is 0.8787mg/μ L; Toluene is 0.8669mg/μ L； O-xylene, m-xylene and p-xylene are 0.8802 mg respectively/μ L, 0.8642 mg/μ L, 0.8611 mg/μ L; 0.8672 mg for Ethylbenzene/μ L; Butyl acetate is 0.8830 mg/μ L; Styrene is 0.9040 mg/μ L; Undecane is 0.740 mg/μ。 Benzene 11.4 at room temperature of 20 ℃ μ l. Toluene 23 It is used to produce PP vertical coffee capsule 1 in the U.S. market in order to achieve the purpose of waterproof or increase the ability of anti leakage μ l. O-xylene, m-xylene and p-xylene are 34.1 respectively μ l、34.7 μ l、34.8 μ l. Butyl acetate 22.60 μ l. Ethylbenzene 23.1 μ l. Styrene 22.1 μ l. Undecane 33.8 μ L put it into a 5ml volumetric flask and fix the volume to the scale with carbon disulfide

1.4 preparation of desorption samples

collect 10L (0.5l/min) of indoor air with an activated carbon sampling tube, insert a certain amount of absorbent cotton (the quantity and tightness are appropriate) into the air inlet of the activated carbon sampling tube, take a known amount of TVOC mixed standard solution on the absorbent cotton, quickly connect with the previously ventilated nitrogen cylinder tube (the flow should not be too large), inject high-purity nitrogen for 3min to fully adsorb it, and move the activated carbon into 1ml plugged test tube, Add 1.0ml of carbon disulfide and oscillate on the oscillator for 1H. Take 1 μ L inject the standard solution and the standard solution into the gas chromatograph to determine the retention time and the peak area, and calculate the desorption rate of each component of VOCs in the sample

2. Results and discussion

2.1 dilute the concentration of the standard solution gradually with the detection limit and lower limit of quantification of carbon disulfide desorption

and inject the sample with the minimum peak amount, that is, the minimum amount that the tested component can respond to on the instrument. The determination is repeated for 12 times. The detection limit is 3 times the standard deviation of the concentration corresponding to the peak height/peak area (s/n=3), and the lower limit of quantification is 10 times the standard deviation (s/n=10)

reconnect the sensor wiring 2.3 method comparison: the same air sample collected in parallel for 6 times containing 10mg/m3vocs was measured at the same time by carbon disulfide desorption and thermal desorption respectively, and the difference between the two methods was investigated. The experiment found that the recovery rate of carbon disulfide desorption was significantly better than that of thermal desorption. By the significance t-test of the difference between the two means (P> 0.01). It shows that there is a very significant difference between the two methods

references

[1] Xu Dongqun, editor in chief. Living environment pollution and health, Beijing: Chemical Industry Press, 2005

[2] Ministry of health of the people's Republic of China. Code for indoor environmental pollution control of civil building engineering (gb503). Beijing: China Planning Press, 2002, 59