CZE for the speciation of arsenic in aqueous soil extracts

Abstract

We developed two separation methods using CZE with UV detection for the determination of the most common inorganic and methylated arsenic species and some phenylarsenic compounds. Based on the separation method for anions using hydrodynamic sample injection the detection limits were 0.52, 0.25, 0.27, 0.12, 0.37, 0.6, 0.6, 1.2 and 1.0 mg As/L for phenylarsine oxide (PAO), p-aminophenylarsonic acid (p-APAA), o-aminophenylarsonic (o-APAA), phenylarsonic acid (PAA), 4-hydroxy-3-nitrobenzenearsonic acid (roxarsone), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenite or arsenious acid (As III ) and arsenate (As V ), respectively. These detection limits were improved by large-volume sample stacking with polarity switching to 32, 28,14, 42, 22, 27, 26 and 27 mg As/L for p-APAA, o-APAA, PAA, roxarsone, MMA, DMA, As III and As V , respectively. We have applied both methods to the analysis of the arsenic species distribution in aqueous soil extracts. The identification of the arsenic species was validated by means of both standard addition and comparison with standard UV spectra. The comparison of the arsenic species concentrations in the extracts determined by CZE with the total arsenic concentrations measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) indicated that CZE is suited for the speciation of arsenic in environmental samples with a high arsenic content. The extraction yield of phenylarsenic compounds from soil was derived from the arsenic concentrations of the aqueous soil extracts and the total arsenic content of the soil determined by ICP-AES after microwave digestion. We found that 6-32% of the total amount of arsenic in the soil was extractable by a one-step extraction with water in dependence on the type of arsenic species.

Arsenic Speciation Analysis by Ion Chromatography - A Critical Review of Principles and Applications

“…In situ heteropolyacid formation with molybdate and UV-detection gave similar DL [118]. Without sensitivity enhancement in UV-detection, DL between 0.1 and 1.2 mg/L have been reported [119] in aqueous soil extracts. UV detection was 10 3 -10 4 times less sensitive compared with ESI MS [120] and with ICP MS [121].…”

Identification of roxarsonemetabolites produced in the system: Soil–chlorinated water–light by using HPLC-ICP-MS/ESI-MS, HPLC-ESI-MS/MS and High Resolution Mass Spectrometry (ESI-TOF-MS)

“…16,23 Due to the water solubility of the majority of the environmentally related arsenic species, high-performance liquid chromatography (HPLC) and capillary electrophoresis are the preferred separation techniques. 24,25 For arsenic speciation analysis, the most popular technique used so far, is HPLC coupled with mass spectrometry (MS). The combination of inductively coupled plasma (ICP) mass spectrometry for elemental identification and electrospray ionization (ESI) mass spectrometry for molecular identification as detector in HPLC is a powerful tool for the identification of unknown arsenic species.…”

“…Each 3 mL of deionized water (DIW) containing roxarsone (740 mg L À1 as As) were added to each 100 mg of soil (size fraction < 0.71 mm) without any pH adjustment. The soil suspensions were shaken manually and kept afterwards in a water bath at 25 C for 24 h under batch conditions. In the following the samples were filtered (RC membrane, 0.45 mm, Sartorius) and centrifuged for 30 min at 13,000 rpm.…”

Fractionation and Speciation of Trace Elements in Soil Solution

“…However, since CE-ICP-MS can combine high separation efficiency with the sensitivity of ICP-MS, it can be considered as the most important recent development in the field of hyphenated techniques [58]. Capillary electrophoresis has been used for arsenic speciation in soil extracts [59].…”