Arsenic and antimony determination by on-line flow hydride generation-glowdischarge-optical emission detection

Hollow cathode (HC) and conventional Aat cathode (FC) glow discharge (GD) o ptical emission spectrometry (OES) were used as detectors for the determina tion of arsenic and antimony by on-line hydride generation (HG) in a flow s ystem. Both radiofrequency (rf) and direct current (dc) sources were invest igated to produce the discharge. The design of the HC and FC and also the p arameters governing the discharge (pressure, He flow rate, voltage, current and delivered power) and the HG (sodium borohydride concentration and reag ent flow rates) were investigated using both cathodes. The analytical perfo rmance characteristics of HG-GD-OES with HC and FC were evaluated for some emission lines of arsenic (193.7, 200.3, 228.8 and 234.9 nm). The best dete ction limit (0.2 mug l(-1))was obtained when the emission line of 228.8 nm was used with FC. Under the same arsenic optimized experimental conditions, the system was evaluated to determine antimony at 259.7, 252.7 and 231.1 n m, 252.7 nm being the emission line which produced the best detection limit (0.7 mug l(-1)). The rf-HC-GD-OES system was applied successfully to the d etermination of arsenic in freeze-dried urine in the standard reference mat erial 2670 from NIST. Finally, a Row injection system was assayed to determ ine arsenic at 228.8 nm, using a dc-GD with both FC and HC. The results ind icated that for low volumes of sample, the HC discharge allows better analy tical signals than the FC, (C) 2001 Elsevier Science B.V. All rights reserv ed.