Ultra-Trace Determination of Arsenic by Platinum-Coated Tungsten Coil Hydride Generation (HG) Atomic Absorption Spectrometry (AAS)

Abstract

A simple, rapid, and sensitive method for the determination of ultra-trace arsenic (III) is reported based on in situ trapping and revolatilization on a platinum (Pt) coated tungsten (W) coil atom trap. First, the analyte species in vapor form were transported by a mixture of Ar and H-2 and trapped on the Pt-coated W-coil heated at 60 degrees C. Next, in the releasing step, the trap was resistively heated to 950 degrees C; the analyte species are revolatilized and transported to the quartz tube atomizer. The NaBH4 concentration, NaOH concentration, HCl concentration, trapping and releasing temperature, trapping time, and hydrogen and argon gas flow rates were optimized. Using these conditions, a limit of detection of 16 ng L-1 was obtained. The precision was evaluated by relative standard deviation corresponding to 4.8% at 1.0 mu g L-1 (n = 11). The surface of the W-coil trap was coated with Pt using electrolytic deposition. Scanning electron microscopy-energy dispersive X- ray (SEM-EDX) analyses were performed to control the surface morphology of the trap. The same trap may be used for at least 350 atomization cycles without losing sensitivity. The accuracy of the proposed method was evaluated by analyzing NIST CRM 1640a (Trace Elements in Natural Water), EnviroMAT (Drinking water), and CRM-023 (Sandy Loam 7) certified reference materials. The measurements of the certified reference materials were in good agreement with the certified values at the 95% confidence level. The developed method was applied to the determination of As in drinking water samples from Mugla province.