Stability study of As(III), As(V), MMA and DMA by anion exchange chromatography and HG-AFS in wastewater samples

Abstract

The stability of arsenic species (arsenate [As(V)], monomethylarsonate [MMA], dimethylarsinate [DMA] and arsenite [As(III)]) in two types of urban wastewater samples (raw and treated) was evaluated. Water samples containing a mixture of the different arsenic species were stored in the absence of light at three different temperatures: +4 degrees C, +20 degrees C and +40 degrees C. At regular time intervals, arsenic species were determined by high performance liquid chromatography (HPLC)-hydride generation (HG)-atomic fluorescence spectrometry (AFS). The experimental conditions for the separation of arsenic species by HPLC and their determination by AFS were directly optimised from wastewater samples. As(III), As(V), MMA and DMA were separated on an anion exchange column using phosphate buffer (pH 6.0) as the mobile phase. Under these conditions the four arsenic species were separated in less than 10 min. The detection limits were 0.6, 0.9, 0.9 and 1.8 micro g L(-1) for As(III), DMA, MMA and As(V), respectively. As(V), MMA and DMA were found stable in the two types of urban wastewater samples over the 4-month period at the three different temperatures tested, while the concentration of As(III) in raw wastewater sample decreased after 2 weeks of storage. A greater stability of As(III) was found in the treated urban wastewater sample. As(III) remained unaltered in this matrix at pH 7.27 over the period studied, while at lower pH (1.6) losses of As(III) were detected after 1 month of storage. The results show that the decrease in As(III) concentration with time was accompanied by an increase in As(V) concentration.

Mobility of arsenic and its compounds in soil and soil solution: The effect of soil pretreatment and extraction methods

“…However, problems can occur with the stability of element species in the solution [24]. The influence of pH [25], soil microbial populations [26,27], and/or root exudates [28] on the stability of arsenic species in soil solution, wastewater or cultivation medium was observed.…”

Fate and Biotransformation of Metal and Metalloid Species in Biological Wastewater Treatment Processes

“…The determination of arsenic compounds is mostly carried out by hyphenated techniques, the main parts being liquid chromatographic separation and element specific detection. By far the most used systems are HPLC-ICP-MS (B'Hymer & Caruso, 2004;Butcher, 2007;Dietz et al, 2007;Francesconi & Kuehnelt, 2004;Gómez-Ariza et al, 2000b;Gong et al, 2002;McSheehy et al, 2001;Rosenberg, 2003;Terlecka, 2005;Wang, 2007) and HPLC-HG-AFS (Francesconi & Kuehnelt, 2004;Gómez-Ariza et al, 2000a;Gong et al, 2002;Ipolyi & Fodor, 2000;Segura et al, 2002;Simon et al, 2004;Terlecka, 2005). Electrospray mass spectrometry hyphenated with LC is a recent advance in arsenic speciation that opens (Nischwitz & Pergantis, 2006).…”

“…The most studied arsenic species are arsenate (As[V]), monomethylarsonate (MMA), dimethylarsinate (DMA), and arsenite (As ([III]; Butcher, 2007), and they can easily separated by HPLC on an anion exchange column using phosphate buffer (pH 6.0) as the mobile phase. Under these conditions the four arsenic species were separated in less than 10 min (Segura et al, 2002). There is a need to develop stabilizing methods for arsenic species in water samples to obtain reliable results.…”

The development and application of hybrid sorbents for determination and selective removal of arsenic(III) and arsenic(V) from water

“…For determination of arsenic species, all the sampling was performed according to a simple sampling procedure without addition of any reagent for stabilization according to Segura et al [146], arsenic species in water are stabile under neutral conditions for a period of 4 months if they are placed in polypropylene bottles in a refrigerator. Before ICP-MS measurements, the samples were acidified with 5.0 % HNO 3 .…”

“…The standard addition method is useful because some unknown variations of the matrix can be prevented, and it was suggested in some studies [146,158]. Good recoveries were found in the samples that contained traces and low concentration of arsenic species.…”