Electrothermal vaporization using a tungsten filament followed by ICP-MS for the determination of arsenic in microsamples

A combined method of electrothermal vaporization and ICP-MS was studied for microtrace analysis. A 5 mu l volume of a sample was placed on a tungsten filament (0.2 mm in diam. x 45 mm) and desolvated electrothermally. Arsenic in the residue was then vaporized by increasing the temperature of the fil ament to 2450 degrees C with the aid of a capacitor (0.22 F) and then carri ed in an argon stream to an ICP torch. The filament was used repeatedly at least 100 times, The relative standard deviation (n = 10) for signal intens ities of 15 pg As was ca. 10%, with an absolute detection limit (3 sigma) o f 1 pg. The proposed method was applied to the determination of arsenic in a certified reference human hair sample, The analytical results obtained fo r the sample (decomposed with 14 M nitric acid and hydrogen peroxide) were 0.35 +/- 0.03 mu g g(-1), which almost coincided with the certified values (0.31 +/- 0.02 mu g g(-1)).