Simultaneous determination of diphenylarsinic and phenylarsinic acids in amended soils by optimized solvent extraction coupled to HPLC-MS/MS

A solvent extraction method coupled to high-performance liquid chromatography with tandem mass spectrometry detection (HPLC-MS/MS) was developed and validated for the simultaneous determination of soil diphenylarsinic acid (DPAA) and phenylarsinic acid (PAA). Several extraction solvents were evaluated with respect to the degree of soil extract-induced matrix effects and the recovery values for DPAA and PAA in the four studied soil matrices. Validation data showed that solvent extraction had a negligible impact on the accurate quantification of DPAA. In contrast, only with disodium hydrogen phosphate extraction did the method give both limited matrix effects (102-107%) with a coefficient of variation <3% (n = 4) and efficient recoveries (77-109%) at two spiking levels (20 and 50 mg kg(-1)) for PAA. The selection of an appropriate extractant was the approach to reduce matrix effects while guaranteeing satisfactory recoveries of soil DPAA and PAA. Chromatographic separation was completed in 37 min and the analytes were detected in positive mode using selected reaction monitoring. MS/MS operating conditions were optimized for both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources. Under optimal conditions the detection limit was 0.01 and 1.00 mu g L-1 for DPAA and PAA. The method detection limits (MDLs) obtained ranged from 2.52 to 3.42 mu g kg(-1) for DPAA and from 0.23 to 0.33 mg kg(-1) for PAA depending on the soil types, and the intraday and interday precision was less than 5% for both analytes at two different concentrations. The method was successfully applied for the simultaneous determination of DPAA and PAA in one-month aged soils, satisfactory recoveries (> 74.03%) were obtained for both analytes. The results show that the proposed solvent extraction method coupled to HPLC-MS/MS analysis can provide accurate and reliable determinations of DPAA and PAA in soil samples. (C) 2015 Elsevier B.V. All rights reserved.