Sequential injection absorption spectrophotometry using a liquid-core waveguide: Determination of p-arsanilic acid in natural waters [An article from: Analytica Chimica Acta]

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Description:
We describe the development, optimization, and application of a novel method for the quantification of p-arsanilic acid (p-ASA), an organoarsenical that is widely used as an animal feed additive, at @mgL^-^1 levels in surface water samples. The method is based on sequential injection-long pathlength absorbance spectrophotometry (SI-LPAS). This method incorporates the selective reactivity of p-ASA with p-dimethylaminobenzaldehyde (DMAB, ''Ehrlich's Reagent'') in the presence of other common environmental organoarsenicals, such as dimethylarsenic acid (DMAA), monomethylarsonic acid (MMAA), and 3-nitro-4-hydroxyphenylarsonic acid (3-NHPAA, Roxarsone). Optimal reaction conditions were studied, namely the pH dependence of the reaction (pH=1.4), volumes of reagent and sample, reagent concentration, reaction time, reaction temperature, and flow rates. A calibration model that was linear over four orders of magnitude was prepared, where y (A"4"5"0, peak height)=0.139x(mgL^-^1)+0.0275 (R^2=0.9984). The limit of detection was 21.2@mgL^-^1 (3@W), and the analysis time was