Experimental Design Optimization of Arsenic Speciation in Groundwater

Abstract

The optimization of a Differential-Pulse Stripping Voltammetry (DPSV) procedure for arsenic speciation determination, using sodium diethyldithiocarbamate (DDTC-Na) as complexing agent, is described. An experimental design methodology was used to select the optimal experimental conditions. A robust regression method was used for the calibrations under these conditions that eliminate anomalous points. Electroinactive As(V) was reduced to As(III) with sodium thiosulfate prior to determination. The detection limit obtained was 1.95 × 10⁻⁹ mol dm⁻³. This procedure was successfully applied to the determination of arsenic speciation in groundwater.

Keywords:

• DDTC
• Differential-pulse cathodic voltammetry
• Speciation
• Trace arsenic determination

Financial support from the Junta de Castilla y León (Burgos 08/04) and the Spanish Ministerio de Ciencia y Tecnología (BQU) is gratefully acknowledged.

Notes

^a SS, sum of squares; DF, degrees of freedom; MS, mean squares; F _ratio: MS_factor/MS_error; P _level, probability level. *Significant factor at α = 0.05.

^a n = 3; α = 0.05.

^b n = 6; α = 0.05.