Speciation of major arsenic species in seawater by flow injection hydride generation atomic absorption spectrometry

Abstract

Arsenic present at 1 microg L(-1) concentrations in seawater can exist as the following species: As(III), As(V), monomethylarsenic, dimethylarsenic and unknown organic compounds. The potential of the continuous flow injection hydride generation technique coupled to atomic absorption spectrometry (AAS) was investigated for the speciation of these major arsenic species in seawater. Two different techniques were used. After hydride generation and collection in a graphite tube coated with iridium, arsenic was determined by AAS. By selecting different experimental hydride generation conditions, it was possible to determine As(III), total arsenic, hydride reactive arsenic and by difference non-hydride reactive arsenic. On the other hand, by cryogenically trapping hydride reactive species on a chromatographic phase, followed by their sequential release and AAS in a heated quartz cell, inorganic As, MMA and DMA could be determined. By combining these two techniques, an experimental protocol for the speciation of As(III), As(V), MMA, DMA and nonhydride reactive arsenic species in seawater was proposed. The method was applied to seawater sampled at a Mediterranean site and at an Atlantic coastal site. Evidence for the biotransformation of arsenic in seawater was clearly shown.

Oxidation state specific generation of arsines from methylated arsenicals based on l-cysteine treatment in buffered media for speciation analysis by hydride generation-automated cryotrapping-gas chromatography-atomic absorption spectrometry with the multiatomizer

“…The first dimension, the cryotrapping and separation of arsines generated from iAs, MAs, DMAs and TMAs(V)O species, regardless of the oxidation state of As, has been well developed and documented [1,9,12,13] and reviewed [14]. The main drawback that has prevented a widespread application of the HG-CT based methods is the labor intensiveness associated with the switching from cooling to heating of the cryogenic trap, which is often controlled manually.…”

“…The demand is usually covered in the case of direct transfer of generated hydride to the atomizer [22] but generally not in the case of the cryogenic trap collection. The use of the conventional externally heated quartz tube for atomization of arsines released from the cryogenic trap [12,15] is rather an exception. Indeed, the sensitivity estimated from published chromatograms [12], substantially lower than reported in the literature [36] for the same atomizer, indicates unsatisfactory performance of the atomizer for this task.…”

“…The use of the conventional externally heated quartz tube for atomization of arsines released from the cryogenic trap [12,15] is rather an exception. Indeed, the sensitivity estimated from published chromatograms [12], substantially lower than reported in the literature [36] for the same atomizer, indicates unsatisfactory performance of the atomizer for this task. The best suited atomizer for this task appears to be the multiple microflame quartz tube atomizer (multiatomizer) [37,38].…”

Arsenic Speciation Analysis in Water Samples: A Review of The Hyphenated Techniques

“…These operations, however, decrease the concentration of arsenic species below the DL for most ICP-MS systems. The pre-treatment also may alter the original sample composition (Cabon and Cabon, 2000). However, it was reported that this interference was efficiently eliminated by collision of ArCl molecules with helium introduced prior to mass spectrometer in reaction cell (Nakazato et al, 2002).…”

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

“…It has been noted that the As(III) profile is depressed at the surface, probably due to more intense photochemical oxidation. Jean Yves Cabon et al [22] also showed that As(III) was not stable in acidified seawater and the rate of conversion of As(III) to As(V) was dependent on the HCl concentration and the salinity. During the phytoplankton bloom all inorganic As(V) was converted to inorganic As(III) and afterwards, all As(III) was rapidly re-oxidised to inorganic As(V).…”