Speciation of arsenic by ion chromatography inductively coupled plasma mass spectrometry using ammonium eluents

Abstract

Original PaperSpeciation of arsenic by ion chromatography inductively coupled plasma mass spectrometry using ammonium eluents A method based on ion chromatography (IC) and inductively coupled plasma MS (ICP-MS) was developed for the speciation of arsenic in water and soil extracts. An anion-exchange column (G3154A/101) was used to separate As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) with excellent resolution. Various ammonium salts, including NH 4 H 2 PO 4 , (NH 4 ) 2 HPO 4 , (NH 4 ) 2 CO 3 , and NH 4 HCO 3 , were examined as eluents to reduce matrix interference from chloride and to solve clogging problems. The best arsenic speciation was obtained within 9 min with excellent resolution and without interference from high chloride concentrations using an eluent containing 7.5 mM (NH 4 ) 2 HPO 4 at pH 7.9. The detection limits for the target arsenic species ranged from 0.1 to 0.4 lg/L with direct injection of sample without matrix elimination. The proposed method was effectively demonstrated by determining arsenic species in contaminated waters and soils of Bangladesh.

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

“…For a direct inlet into the ICP MS at 1 mL/min, phosphate concentration should clearly be lower than 15 mmol/L since at this concentration a rapid damage of expensive cones [159] and a drop in sensitivity due to clogging [160] was reported. Recently it has been shown that ammonium instead of Na-salts in the plasma produce less deposits [161]. Eluent splitting before the instrument inlet was used too in order to reduce the P-load.…”

“…Hence, approaching pH 7, phosphate is much more ionized which drastically increases its eluent strength. This was used to selectively increase the t R of DMA (pK a = 6.1) while the t R of other species remained [161]. Further deprotonation at higher pH, however, counteracts the selectivity among other As-species since the increased negative charge on phosphate shortens t R of arsenicals [157,161].…”

“…This was used to selectively increase the t R of DMA (pK a = 6.1) while the t R of other species remained [161]. Further deprotonation at higher pH, however, counteracts the selectivity among other As-species since the increased negative charge on phosphate shortens t R of arsenicals [157,161]. This makes the separation of the most toxic AsIII from the non toxic AB impossible [52] as the two are separated only at a higher eluent pH (e.g.…”

Speciation and determination of bioavailable arsenic species in soil samples by one‐step solvent extraction and high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

“…Phosphate shares many similar chemical properties to arsenate, such as ion size and acid dissociation constants, and provides a mild extraction medium similar to environmental conditions . Therefore, ammonium phosphate buffer was selected as the primary extractant for arsenic extraction from soils in this study.…”

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

“…Majority of the papers published on arsenic speciation in the past few years used (HPLC) as the basis of separating the species [108], this is usually coupled with mass spectra detector [109,110], (HG) [111], sensitive optical spectroscopic detection system such as (AFS) [112], (AAS) [113,114], (ICP-MS) [115], ion-pair reversedphase chromatography (IP-RP-HPLC) [116,117], and (IE-HPLC) [118,119]. That most studies agree with the use of HPLC which provided high efficiency of separation for very low concentration of the arsenic species, many of researchers agreed to couple (HPLC) with (ICP-MS) for measurement.…”