Investigation of arsenic speciation in algae of the Antarctic region by HPLC-ICP-MS and HPLC-ESI-Ion Trap MS

Abstract

An investigation into presence and nature of As species in algae originating from the Antarctic region is presented in this work. Arsenic speciation information in Antarctic algae samples was obtained by using anion- and cation-exchange chromatography with on-line detection by inductively coupled plasma spectrometry (ICP-MS) or electrospray ionization ion trap mass spectrometry (ESI-ITMS). Total arsenic concentrations found by ICP-MS in the Antarctic algae samples ranged from 8.4 to 29.3 μg As g⁻¹ (dry weight). Arsenic species were efficiently extracted (83–108%) by using an MeOH : H₂O (1 : 1) mixture. Anion-exchange chromatography utilizing gradient elution with 25 mM ammonium bicarbonate adjusted to pH 10 was used to separate the anionic As species present in the algae extracts. Additionally, gradient cation-exchange chromatography was performed using 4 mM pyridine solution adjusted to pH 2.4. This allowed the separation of neutral and cationic As species present in the algae extracts. High volatility of the mobile phases allowed sample introduction compatibility with both ICP-MS and ESI-ITMS detectors. Three arsenosugar species (arsenosugar–OH, –SO₃, and –PO₄) previously reported in marine algae samples accounted for ∼50–80% of the total extractable arsenic in 4 of the 5 samples studied. In one algae sample, the presence of a previously unreported arsenic-containing compound in algae samples was confirmed by ESI-ITMS isolation and fragmentation as 5-dimethylarsinoyl-β-ribofuranose. This compound has been identified previously in marine bivalves but, to our knowledge, not in algae samples.