Air TVOC gas chromatography analysis method
Toxic and harmful substances in the indoor air will damage the health of the human body. The Code for Indoor Environmental Pollution Control of Civil Buildings will make hydrazine, formaldehyde, ammonia benzene and volatile organic compounds (TVOC) and free toluene diisocyanate (TDI) as the primary. Contaminants. This article gives a general introduction to the gas chromatographic analysis of volatile organic compounds (TVOC).
(1) Instrument configuration (required analysis equipment):
1. Thermal desorption instrument thermal desorption (with TVOC adsorption tube)
2. Gas chromatograph of FID detector equipped with GC9800 of Jinan Fine Testing Technology Co., Ltd.
3. Atmospheric sampler
4, TVOC standard sample
5. Columns suitable for TVOC analysis
6 chromatography workstation
7, nitrogen and hydrogen air source (for chromatography)
(2) The specific analysis conditions and processes are as follows:
1. Use the atmospheric sampler and TVOC adsorption tube to sample on site: 0,5L/min for 20min or 10L atmosphere. That is, the 10L atmosphere passes through the adsorption tube at a flow rate of 0,5 L/min, and the total volatile organic compounds in the air are adsorbed in the adsorption tube and brought into the laboratory for detection;
2. Start the gas chromatograph: 0,32mm*50mTVOC capillary column; FID: 260°C; vaporization: 260°C; column chamber: 50°C constant for 10min, rise to 250°C at 5°C/min; 250°C to peak output; Sensitivity and attenuation: 103*1; calibration: 1μL of each standard content of 100mg/mL was calibrated to the adsorption tube with a scaler, and blown with 100mL/minN2 for 5min, this tube is the standard adsorption tube; Thermal desorption temperature: 300 ° C, pyrolysis for 30 seconds, after 5 minutes of injection, return to the pyrolysis instrument, the split ratio is 50:1
3. According to the above conditions, the standard adsorption tube is first prepared. After the drawing, the calibration curve (factor) is obtained by the external standard method, and then the TVOC chromatogram in the adsorption tube is sampled and qualitatively quantified under the same chromatographic conditions.
4. Calculation:
a According to the above method, the integral result table can directly obtain the content M of each component of TVOC in the sampling tube, the unit is μg;
b Find the total amount of TVOC M = M1 + M2 + M3 + - Mi + M (g). The total amount includes a set volatile content M = f (toluene) × ∑ A, that is, the amount of the unidentified substance is calculated as the correction factor of toluene.
c find the actual total TVOC of the air M = M total - M blank total
d Determine the concentration of TVOC in the measured indoor air C total M real (μg) / V0 (L) (mg / m3)
V0 is the sampling volume corrected to the standard state, V0V is × (T0/273+t) × (P/P0) (L)
5. Judgment and report: According to the calculation result, C is judged according to the GB index, and the conclusion is drawn and a report is issued.
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