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

Abstract

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 b 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 μg L −1 for DPAA and PAA. The method detection limits (MDLs) obtained ranged from 2.52 to 3.42 μg 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 (N 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.

Speciation and sorption structure of diphenylarsinic acid in soil clay mineral fractions using sequential extraction and EXAFS spectroscopy

“…Following these steps, two additional wash steps were performed using NH 4 -oxalate to remove residual DPAA from the solution, as described by Wenzel et al (2001). Extracts from each step were analyzed for DPAA content using a high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) method with low matrix effect (102-107%), detection limit (0.01 μg L −1 ), and intraday and interday previsions (< 5%) (Zhu et al 2016a). The amount of DPAA sorbed (Q ads , mg kg −1 dry clay mineral fractions) was calculated as the sum of the DPAA extracted in the five-step SEP.…”

Contrasting effects of iron reduction on thionation of diphenylarsinic acid in a biostimulated Acrisol

“…Four serum bottles were centrifuged at each sampling point, the supernatants were used for the analysis of dissolved DPAA, inorganic As, sulfate, sulfide, Fe(II), Mn(II), and total organic carbon (TOC), and the residues from the centrifuged supernatants were freeze-dried and used for the analysis of solid phase-associated DPAA, total sulfur, and carbon in the solid phase. The fractions of DPAA were determined using an HPLC-MS/MS method, with all samples diluted to give limited matrix effect (102-107%) (Zhu et al 2016b). Dissolved inorganic As was determined using AFS.…”

Solid-solution partitioning and thionation of diphenylarsinic acid in a flooded soil under the impact of sulfate and iron reduction

“…Different organic arsenic species were detected and quantified by a method described in our previous study (Zhu et al, 2016) using high performance liquid chromatography (HPLC) with a Sunfire C 18 3.5 μm, 2.1 mm × 150 mm column (Waters, Milford, USA) and a Sunfire C 18 3.5 μm, 2.1 mm × 10 mm guard column (Waters, Milford, USA). The mobile phase was H 2 O containing 0.1% formic acid and CH 3 OH containing 0.1% formic acid.…”

“…The sum of the dissolved DPAA and DPAA in the residue was defined as total DPAA and the fraction of DPAA associated with the solid phase was calculated by the difference between the total and dissolved DPAA (total volume 30 mL). Here, Na 2 HPO 4 was selected as an extractant based on our previous study (Zhu et al, 2016).…”