Liquid chromatography electrospray mass spectrometry with variable fragmentor voltages gives simultaneous elemental and molecular detection of arsenic compounds

Abstract

A single quadrupole high performance liquid chromatography electrospray mass spectrometry system with a variable fragmentor voltage facility was used in the positive ion mode for simultaneous recording of elemental and molecular mass spectral data for arsenic compounds. The method was applicable to the seven organoarsenic compounds tested: four arsenic-containing carbohydrates (arsenosugars), a quaternary arsonium compound (arsenobetaine), dimethylarsinic acid, and dimethylarsinoylacetic acid. It was not suitable for the two inorganic arsenic species arsenite and arsenate. In the case of arsenosugars, qualifying ion data for a characteristic common fragment (m/z 237) was also simultaneously obtained. The method was used to identify and quantify the major arsenosugars in crude extracts of two brown algae.

Multidimensional liquid chromatography with parallel ICP MS and electrospray MS/MS detection as a tool for the characterization of arsenic species in algae

“…This observation was independently made by Pedersen and Francesconi [17]. A small peak eluted near the solvent front which could not be unambiguously assigned because of the limited separation efficiency in this region [17]. Arsenosugars C and B have not been previously reported in Laminariales, despite their being referred to as arsenic constituents in other brown algae.…”

“…In our previous work on the same algae we could see arsenosugars A and D, but the quality of mass spectra was poor because of the insufficient matrix removal [9]. This observation was independently made by Pedersen and Francesconi [17]. A small peak eluted near the solvent front which could not be unambiguously assigned because of the limited separation efficiency in this region [17].…”

“…In our former work, two arsenosugars in Hizikia and Laminaria algae were detected by ES MS/MS after twodimensional HPLC [8,9]. The same sugars were detected independently in Laminaria and one more in Hizikia algae by LC-ES MS using variable fragmentor voltages to allowing controlled fragmentation of analyte species [17].…”

“…An ammonium carbonate buffer, which allowed the baseline separation of anionic As species and was compatible with an electrospray ion source [15,17,21], was chosen for preparative anion-exchange separations. A chromatogram obtained (Fig.…”

“…The insufficient sensitivity of ES MS/MS problematic matrix suppression effects, and the impossibility of unambiguous attribution of peaks in mass spectra to arseno-compounds meant that only a few major species could be targeted. Variable fragmentor voltage [17] or the parallel use of ICP MS [8,9] was necessary to obtain assurance of arsenic presence in the molecular ion. An elegant demonstration of ES MS for the identification of an unknown organoarsenic compound was recently reported [18].…”