AUTOMATED TECHNIQUE FOR SUB-MICROGRAM DETERMINATION OF SELENIUM AND ARSENIC IN SURFACE WATERS BY ATOMIC-ABSORPTION SPECTROSCOPY

The technique employs sodium borohydride for conversion of selenium and arsenic compounds in specimens to hydrogen selenide and arsine. To increase the efficiency of hydride recovery for analysis, the reacted specimen is stripped using a heated column. The hydride gas and hydrogen evolved from the chemical reaction is then combusted in a tube furnace placed in the optical path of an atomic absorption spectrophotometer. Seventy specimens can be analyzed per hour with a detection limit of 0. 019 mu g/liter for selenium and 0. 011 mu g/liter for arsenic.