Air quality - Determination of sulfuretted hydrogen, methyl sulfhydryl, dimethyl sulfide and dimethyl disulfide - Gas chromatography
1 Application scope
1.1 This method is applicable to the simultaneous determination of sulfuretted hydrogen, methyl sulfhydryl, dimethyl sulfide and dimethyl disulfide in the exhaust of malodorous pollution sources and the ambient air. The limits of detection of the four components in flame photometric detector of gas chromatograph (GC-FPD) are 0.2 × 10-9 ~ 1.0 × 10-9 g. If the concentration of the four components in the gas sample is higher than 1.0 mg/m3, 1 ~ 2 mL of gas sample may be directly injected into gas chromatograph for analysis. Concentrate 1 L of gas sample and the limits of detection of the four components are 0.2 × 10-3 ~ 1.0 × 10-3 mg/m3.
2 Principle
In this method, a vacuum-treated 1 L gas cylinder is used to collect malodorous gas samples from fugitive emission sources or ambient air sample, and a polyester plastic bag is used to collect malodorous gas sample from exhaust pipes. Gas sample with high sulfide content may be directly taken with syringe for 1 ~ 2 mL and injected into gas chromatograph equipped with flame photometric detector (FPD) for analysis. If the absolute amount of sulfide in the direct injection volume is lower than the detection limit of the instrument, the sulfide in 1 L gas sample shall be concentrated by a concentration tube at low temperature with liquid oxygen as refrigerant. After concentration, the concentration tube is connected to the analysis system of chromatograph and heated to 100°C, so that all concentrated components flow through a chromatographic column for separation, and various sulfides are quantitatively analyzed by FPD. In a certain range of concentration, the logarithm of sulfide content is proportional to that of chromatographic peak height.
3 Reagents and materials
3.1 Reagent
3.1.1 Benzene (C6H6): analytical grade (toxic), without interference peak after chromatography. If there is an interference peak, it needs to be redistilled in a glass distiller.
3.1.2 Sulfuretted hydrogen (H2S): The purity is more than 99.9%, and the hydrogen sulfide prepared in the laboratory needs to be calibrated.
3.1.3 Methyl sulfhydryl (CH3SH): analytical grade.
3.1.4 Dimethyl sulfide [(CH3)2S]: analytical grade.
3.1.5 Dimethyl disulfide [(CH3)2S2]: analytical grade.
3.1.6 Phosphoric acid (H3PO4): analytical grade.
3.1.7 Acetone (CH3COCH3): analytical grade.
3.1.8 Liquid oxygen.
3.2 Carrier gas and auxiliary gas of chromatograph
Foreword i
1 Application scope
2 Principle
3 Reagents and materials
4 Apparatus
5 Samples
6 Analysis operation
7 Representation of results
8 Precautions
