Study On Electrochemical Hydride Vapor Generation Atomic Fluorescence Spectrometry

In this paper,a new style of electrolytic cell to reduce deadvolume and enhance signal intensity was designed and used as the sample introduction interface for atomic fluorescence spectrometry(AFS).With this cell,methods for the determination of four arsenic species by ion exchange chromatography(IEC)-electrochemical hydride vapor generation(EcHG)-AFS and the determination of total arsenic by EcHG-AFS were developed.The main contents and results were as following:(1)Based on the review of arsenic speciation analysis techniques and the research progress of EcHG,through continuous improvement of the design and the decrease of the dead volume and the shape of the electrolytic cell,a new type of efficient online electrolytic cell was designed and developed.The electrode and the chemical compostion of electrolyte for anothode cell were also optimized to enhance the online hydride generation efficiency.(2)The electrolytic cell was used as an interface to combine liquid chromatography(with anion exchange column)and AFS detector to develop an elemental speciation analysis system for As(Ⅲ),As(Ⅴ),dimethylarsine(DMA),and monomethylarsine(MMA)measurements.Under the optimized operating condition,that is,AFS detector with carrier gas flow rate of 1000 mL/min,hydrogen flow rate of 170 mL/min,negative high voltage of 400 V for photomultiplifier tube(PMT),and current of 140 mA for hollow cathode lamp(HCL)excitation,and EcHG with electrolytic current of 1.7 A,catholyte concentration and flow rate of 1.0 mol/L sulfuric acid and 0.2 mL/min,anolyte concentration and flow rate of 2.0 mol/L sulfuric acid and 1.0 mL/min,better analytical performance could be achieved.Under those optimized parameters,method precision(represent as relative standard deviation,RSD)was in the range of 1.5%(As(V)20.0μg/L)-3.7%(DMA 4.0 μg/L)(n=7).The detection limits(3σ,n=7)were As(Ⅲ)0.10 μg/L,DMA 0.21 μg/L,MMA 0.30 μg/L,and As(V)1.04 μg/L,respectively.The liner relationship of analyzed As(III),DMA,MMA and As(V)could be achieved in the range of 0.2～10.0 μg/L,0.4-20.0 μg/L,1.0～20.0 μg/L,2.0～100.0 μg/L,respectively.This developed method could be applied to the determination of four arsenic species in the water sample collected from Furong Lake and Furong Reservoir in Xiang’an Campus,Xiamen University.(3)The electrolytic cell for electrochemical hydride reaction was used as an online sample introduction system for AFS to directly measure total As in surfacewater.After optimization of the AFS operating parameters,and the electrolytic current,catholyte and sample flow rate of the online EcHG condition,when electrolytic current 1.7 A,and catholyte and sample flow rate 1.5 mL/min,higher fluorescence signal intensity and better noise to ratio of As(Ⅲ)could be yielded.The possible interferences of continuum inorganic anions(Cl-,NO3-,SO42-,PO43-)and ions(Ca2+,Mg2+,K+,Cu2+,Co2+,Zn2+,Fe3+,Ni2+,CrO42-,Mn2+,Pb2+)on the As(Ⅲ)in EcHG procedure were also investigated,which showed that there were no obviously interferences on the detection of ultra-trace level of As(Ⅲ).The analytical performance of this developed method was that RSD 1.7%(1 μg/L,n=7),detection limit(3σ,n=7)0.020 μg/L,linear range from 0.05 to 10.00 μg/L.The method also was applied to the determination of the total arsenic in the surface water samples from Furong Lake and Furong Reservoir of Xiang’an Campus,Xiamen University.And good recovery of standard added was obtained which was between 96.6%and 118.0%in the experiment.