EMISSION CHARACTERISTICS OF CHROMIUM IN HOLLOW ANODE-FURNACE ATOMIZATION NONTHERMAL EXCITATION SPECTROMETRY

Emission parameters for the determination of Cr using hollow anode-furnace atomization non-thermal excitation spectrometry (HA-FANES) were investigated. The spectral background between 280 and 400 nm included strong emission bands from CN, NH and CH. The best signal-to-noise ratio for Cr was observed for the atomic line at 359.3 nm. Argon atomic emission (420.1 nm) showed no decrease in intensity in the presence of thermionic electrons while Ar ionic emission (434.8 nm) showed a dramatic decrease in intensity. The integrated Cr emission signal exhibited a broad maximum between atomization temperatures of 1800 and 2100-degrees-C. Peak areas increased with pressure with the best signal-to-noise ratio found at 160 Torr (21 300 Pa). The discharge current ranged from 10 to 90 mA with the optimum current dependent on the pressure. A limit of detection of 0.8 pg was obtained for an Ar pressure of 160 Torr, a current of 70 mA, and an atomization temperature of 2000-degrees-C. This limit of detection is comparable to conventional GFAAS and a factor of five better than hollow cathode FANES (HC-FANES). The accuracy of the technique was assessed by the determination of Cr in a standard reference water (SRM 1643b).