Determination of Alkyl Mercury in Water: Purge and Trap/Gas Chromatography-Cold Atomic Fluorescence Spectrometry
Distillation-ethylation Determination of Methmercury in Natural Water by GC-CVAFS
Sample distillation of alkylmercury in the sample to be tested (water quality) is used as a pretreatment method for the determination of alkylmercury in water quality in “HJ 977–2018”, different from “GB/T 14204–93” and “GB/T 17132–1997” “mercapto cotton enrichment — hydrochloric acid sodium chloride solution desorption — toluene extraction”, the purpose of distillation is to remove the interference of matrix and Hg2+ in the water sample. The principle of the instrument is as follows:
Since methylmercury will be adsorbed on the wall of the polyethylene plastic bottle and the temperature is high during the distillation process, in order to avoid the adsorption of alkylmercury during the distillation process, the distillation bottle, the receiving bottle and the connecting pipeline are made of Teflon (polytetrafluoroethylene) material.
Teflon PFA distillation bottle:
Sample preparation
Measure 45 ml of the sample into a 60ml steaming bottle, add 4.5 ml of water and 500 ul of acid acetate-sodium acid buffer solution (5.12) into the receiving bottle, and shake well.
Set the temperature of the heating device at 125C~130C in advance, and connect the retentate flask and the receiving flask with a polytetrafluoroethylene pipeline to ensure that the retort flask is sealed. First put it into the distillation bottle for heating, and then put the receiving bottle into the cooling device when the vapor enters the receiving bottle to prevent the liquid in the receiving bottle from freezing.
When about 80% of the sample volume is evaporated (the volume of the liquid in the receiving bottle is about 41 ml, and the whole evaporation process lasts about 3h~4h), stop the distillation, and the pH value of the distillate at this time is 5.0~6.0. The steaming process is shown in the figure. If the distillation volume of the sample exceeds 85%, check the pH value of the distillate with pH test paper, if it is less than 5.0, the sample is invalid. The distillate should be stored at room temperature and protected from light before analysis, and analyzed within 48 h.
Configuration:
1. PFA distillation vessel 60mll: 3–6 pieces
2. PTFE cover: 1 piece
3. Heating device: 1 set
4. Teflon connecting pipe: FEP1/4 1.5 meters