A Novel Method For The Determination Of Arsenic Based On Chemical Vapor Generation Coupled To Atomic Fluorescence Spectrometry

It is reported in the literatures that volatile arsenic trichloride can be generated from the reaction between As (III) and concentrated hydrochloric acid, while As(V) can not. By use of this observation, a new method for the determination of As(III) was proposed, with atomic fluorescence spectrometric detection. And the method could also be applied to the indirect determination of As(V) after prereduction.In this work, samples were decomposed firstly, then, according to the nature of the analyte,10% KI solution or mixture of 10% Thiourea and 10% L-ascorbic acid were used as prereductants to reduce As(V) into As(III) in the samples, respectively. The optimized instrumental conditions for the measurements were as follows: hollow cathode lamp current of 70 mA, photomultiplier tube negative voltage of 350 V, observation height of 8 mm, and shield gas (argon) flow rate of 1000 mL/min. In order to obtain the optimum condition for the present method, the effect of different parameters, such as argon flow rate, hydrogen flow rate, sample and reagent acidity, and carrier acidity were investigated in detail. Furthermore, the selectivity of this new method was evaluated by studying the effect of various cations and anions including transition metals on the determination of 0.1 mg/L As (III). The foreign ions were added as their chloride salts or other salts. The results clearly showed that chloride generation provides superior performance with respect to tolerance to various cations and anions, especially, to transition metal ions compared to hydride generation.Under the optimized experimental conditions, the present procedure allows quantitation of arsenic in the concentration range of 0.01~ 4.0 mg/L, with a detection limit (3σ) of 6.0μg/L. The relative standard deviation (RSD) is 4.0% for 0.1 mg/L arsenic (n=7). Finally, the proposed method was successfully applied to the determination of arsenic in several certified reference materials (stainless steel, alloy steel, copper alloy and water sample) as well as real samples (brass material and spiked cobalt samples), and the results were in good agreement with those certified values or the ICP-MS results. In general, the method is simple, sensitive and interference-free, and especially appropriate for the arsenic determination of steel, alloy and the alike samples which contain high contents of transitional metals.