Abstract
A method of preconcentration with iron (III) was studied for graphite furnace atomic absorption spectrometry (GFAAS) of trace amount of chromium in sea and river waters. A ten milliliters of 10 w/v% ammonium carbonate buffer was added to 100 ml of sample water, the pH of which was adjusted to about 7.5, followed by adding 3 mg of iron (III). Only chromium (III) was quantitatively coprecipitated. The coprecipitate was collected onto a membrane filter paper. Chromium (VI) was then coprecipitated by adding (1+11) HCl of 20 ml and 3 mg of iron (II) to the membrane filtrate, and adjusting the pH to about 7.5. The coprecipitate was also collected onto another membrane filter paper. The precipitate containing chromium (III) was dissolved with 25 ml of (1+20) HCl, and the solution was used as the sample solution for GFAAS. The linear range of calibration curve was from 0.5 to 5μg/l, and the detection limit for chromium was 0.26μg/l, and the lower limit of determination was 0.85μg/l in the case of using 100 ml of sample water. This method was not influenced by sample water from 100 to 1,000 ml, and was satisfactorily applied to the separation analysis of trace of chromium in sea water and river water.
