Determination of arsenic content in natural water by graphite furnace atomic absorption spectrometry after collection as molybdoarsenate on activated carbon.

A sample solution containing less than 0.5 mug of As was adjusted to pH 2. As in the solution was collected on activated carbon (AC) as molybdoarsenate. The AC was directly introduced as an AC suspension into a graphite furnace atomizer, and the concentration of As was determined by atomic absorption spectrometry (AAS). This method is relatively free from interference caused by coexisting ions. The calibration curve was linear up to 0.1 mg l(-1), and limit of detection of As was 0.004 mg l(-1). When 1000 ml of sample solution is preconcentrated to 5 ml (enrichment factor is 200-fold) 0.02 mug l(-1) of As could be determined, and relative standard deviation was below 4.0% (by the deuterium background correction system). The method was applied to sea water and well water, and the sum of As(III) and As(V) was determined with satisfactory results.