A solid phase extraction method for the determination of gold(III) at trace levels by flame atomic absorption spectrometer (FAAS) was developed. The method was based on retention of gold as chloro complexes through the Amberlite XAD-2000. The effect of some analytical parameters including hydrochloric acid concentration, sample volume, sample and eluent flow rates, eluent volume, eluent concentration and interfering ions on the recovery of gold(III) was investigated. The retention of gold(III) from 1.5 mol l(-1) HCl solution and the recovery of gold with 0.07 mol l(-1) NH3 solution were quantitative (>or=95%). The relative standard deviation (RSD) was calculated as 3.2% (n = 10). The detection limit for gold was 2 microg l(-1). The accuracy was checked with the determination of gold spiked an artificial seawater and a pure copper samples.

A quartz crystal microbalance sensor has been developed for the determination of inorganic arsenic species in water. The gold electrode surface was modified by a self-assembled layer of dithiothreitol, and the frequency change of the modified crystal was proportional to the arsenic concentration from 0 to around 50 mg L À1 , a range which spans the current US EPA maximum contaminent level of 10 mg L À1 in drinking water. As dithiothreitol is capable of reducing arsenate to arsenite, the sensor detects both species. The method was applied to the determination of arsenic in spiked rain, tap, pond and bottled water; recoveries not significantly different from 100% were obtained for a number of spike additions of less than 10 mg L À1 . Arsenic was only detected in the bottled water sample, at a concentration of 8 mg L À1 . This method is simple, fast, and inexpensive compared with other conventional arsenic detection methods, and has the potential to be used in the field.

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A simple spectrophotometric method was optimized for the speciation vanadium using pyrocatechol violet as chelating agent. Vanadium(V) was determined by pyrocatechol violet at pH 3.0, whereas vanadium(IV) was simultaneously determined using same procedure after oxidation of vanadium(IV) by potassium permanganate. The linear range for vanadium(V) is 0.2-4.0 μg/mL with a detection limit of 0.038 μg/mL. The proposed spectrophotometric method was found selective for vanadium(V) with high tolerence limit of foreign ions. The proposed method was validated by standard addition method at different levels of both understudied species with >92 % recoveries in water, black pepper and coal samples.