DETERMINATION OF ARSENIC IN AMBIENT WATER AT SUB-PART-PER-TRILLION LEVELS BY HYDRIDE GENERATION PD COATED PLATFORM COLLECTION AND GFAAS DETECTION

A method for trace determination of total arsenic in ambient waters is described. Arsenic is separated on-line from a large volume water sam ple by hydride generation and purging, pre-collected on a Pd coated py rolytic platform cuvette using a simple and inexpensive system, and fi nally detected by GFAAS. Instrument parameters, hydride generation, tr ansportation, and collection were optimized. The analytical behavior f or major species including As3+, As5+, monomethyl As (MMA), and dimeth yl As (DMA) were investigated individually. Problems arising from use of the system were discussed and eliminated. The necessity of sample d igestion and an efficient digestion method were studied. Sample digest ion for water with low organic content such as tap water and clean gro und water and some clean surface water can be omitted. The method dete ction limit (MDL) is 0.3 ng l(-1) for a 25 ml water sample. Recoveries close to 100% with R.S.D. < 5% can be easily achieved. Typical aqueou s samples including tap, ground, lake, river, rain, sewage effluent, a nd saline water from different origins in the US, China, and Canada we re collected and analyzed using ultra clean sampling and analysis tech niques. The background levels of As in most water analyzed were establ ished for the first time, and found to be far above the EPA's health e ffect criteria, 18 ng l(-1). (C) 1998 Elsevier Science B.V. All rights reserved.