Development Of Analytical Instrument For Alkyl Mercury Speciation In Environmental Water

The alkyl mercury is low in environmental water.Due to its lipophilic property,it is easily enriched by aquatic organisms and enters human body through the food chain.Its toxicity is stronger than inorganic mercury.On the other hand,methyl mercury is important in the mercury geochemical cycle,and it is related to circulation,migration and transformation of mercury in ecosystems geochemical cycle.Therefore,it is important to determine alkyl mercury.Because alkyl mercury is very low in environmental water,it is difficult to determine at ultra-trace level by general instruments.This method,purge and trap-gas chromatography-cold atomic flourescence spectrometry system,is applicable for determination of ultra-trace alkyl mercury speciation in environmental water.The existing instrument is expensive and its high temperature pyrolysis device consumes high energy,it is not suitable for small and medium-sized laboratories.This analytical instrument for alkyl mercury speciation was based on atomic fluorescence spectrometer,to construct a purge and trap-gas chromatography-dielectric barrier discharge-cold atomic fluorescence spectrometry system.The instrumental system were designed including a derivatized bottle of purge and trap unit,a packed column thermotank of gas chromatography unit,a dielectric barrier discharge device and a fluorescent cell of cold atomic fluorescence spectrometer unit.The instrumental single-way trap system was constructed with some three-way solenoid valves.The analysis of ultra-trace alkyl mercury was finished by this instrument.The performances of instrumental hardwares were evaluated.The derivative bottle has a good air tightness.The accuracy of the thermotank was±0.2°C.The dielectric barrier discharge device had a stable discharge and a long life.The fluorescent cell structure was simple and was installed easily.About this instrument,the overall size was small and the energy consumption was low,which were conducive to commercizlization.The instrumental conditions were chosen by determining methyl mercury when derivating agent was sodium tetraethylborate.The conditions were optimized including gas flow of purge and trap unit,flow rate of argon,packed column temperature,thermal desorption temperature,sample volume,dose of derivating agent,drying tube and power of dielectric barrier discharge device.The precision,detection limit and coexisting ion effect were evaluated.The lake water and river water samples were determined.The instrumental optimum conditions were enumerated.The derivative reaction time was 12 min.The purge time was 10 min.The purge flow rate of nitrogen was 400mL/min.The sample volume was 50 mL.The volume of sodium tetraethylborate solution was 50?L.The flow rate of argon was 10 mL/min.The packed column temperature was 80°C.The heat release device was set to 105°C.The power of dielectric barrier discharge device was set to 5 W.There was a dry tube.The methyl mercury was determined in optimum conditions with peak area as the analytucal parameter.The instrumental precision(RSD,n=6)was 2~6%,and the correlation coefficient(R~2)of calibration curve was 0.9993,and the limit of detection was 0.02 ng/L.Yanhu lake water and Dongfeng river water were determined.The determined values(mean value±2SD,n=3)were 0.02±0.01 and 0.03±0.02 ng/L,respectively.The recoveries for adding standard were between 84~106%.