Flow injection hydride generation atomic absorption spectrometry for determination of arsenic in water and biological samples from arsenic-affected districts of West Bengal, India, and Bangladesh

The increasing concern over human exposure to arsenic in West Bengal and Ba ngladesh has necessitated the development of a rapid method for determinati on of trace levels of arsenic in water and biological samples. We have deve loped a simple indigenous flow injection hydride generation atomic absorpti on spectrometry (FI-HG-AAS) system for the determination of arsenic in part s-per-billion levels in water and biological samples. The technique is fast , simple, and highly sensitive. The accuracy and precision of the method we re evaluated by spiking known amounts of arsenic and analyzing different ty pes of environmental and biological standard reference materials. The organ ic matter in a biological sample was destroyed by acid digestion and dry as hing technique. We analyzed thousands of tubewell water samples from the af fected districts of West Bengal and Bangladesh. Most of the water samples c ontained a mixture of arsenite and arsenate and in none of them could we de tect methylated arsenic. We also analyzed thousands of urine (inorganic ars enic and its metabolites), hair, and nail sample and hundreds of skin-scale and blood samples of people drinking arsenic-contaminated water and showin g arsenical shin lesions. Quality control was assessed by interlaboratory a nalysis of hair samples. An understanding of arsenic toxicity and metabolis m requires quantitation of individual arsenic species. The techniques we us ed for the determination and speciation of arsenic are (i) separation of ar senite and arsenate from water by sodium diethyldithiocarbamate in chlorofo rm followed by FI-HG-AAS; (ii) determination of arsenite in citrate/citric buffer at pH 3 and total arsenic in water in 5 M HCl by FI-HG-AAS. Thus, ar senate is obtained from the difference: (iii) for analysis of inorganic ars enic and its metabolites in urine FI-HG-MS was used after separation of the species with a combined cation-anion exchange column. Total arsenic in uri ne was also determined by FI-HG-AAS after acid decomposition. The species a rsenite and arsenate are present in groundwater in about a 1:1 ratio and ab out 90% of the total arsenic in urine is present as inorganic arsenic and i ts metabolites. (C) 1999 Academic Press.