Investigation of Arsenic species found in Antarctic algae by using cross-information obtained with LC-ICP-MS and LC-ion trap MS

WUILLOUD, RODOLFO G.; ALTAMIRANO, JORGELINA C.; SMICHOWSKI, PATRICIA; HEITKEMPER, DOUGLAS

Nashville, Tennesse

Conferencia; 52nd ASMS (AMERICAN SOCIETY OF MASS SPECTROMETRY) CONFERENCE ON MASS SPECTROMETRY AND ALLIED TOPICS); 2004

AMERICAN SOCIETY OF MASS SPECTROMETRY

Arsenic speciation is necessary due to the extreme toxicity differences that its compounds have in the environment and biological systems. This element can be accumulated in marine plants and animals up to concentrations of several hundreds of mg kg-1. Moreover, As biotransformations in marine life are known to produce a wide range of organoarsenic compounds. Therefore, species-specific determination of these compounds is of considerable interest.  Although, several publications have dealt with As speciation in seaweed samples, to our knowledge, no information on As species in Antarctic algae have been presented thus far. For the first time, investigation on the natural occurrence of As species in Antarctic algae is presented in this work. Anion-exchange chromatography with an IonPac AS7 (4 x 250 mm) column was used for the chromatographic separation of the As species in the Antarctic algae extracts.  The chromatographic separation of As species was performed with a mobile phase containing ammonium carbonate at a pH 10.0 and flow rate of 0.8 mL min-1.  The injection volume was 5 ?ÝL.  The separation conditions used were compatible with both ICP-MS and ion trap MS detectors. The HPLC system was coupled on-line with ICP-MS or ion trap MS for element-specific detection and qualitative analysis, respectively. Several chromatographic parameters were varied to obtain complete resolution of the As species including ionic strength gradients and mobile phase pH. Antarctica is still a pristine continent, and it is a unique observation site to investigate global change phenomena that eventually will have an impact on more inhabited lands. Samples from that origin, therefore, are of particular significance with regards to speciation studies on a very widespread element such as As. Since Antarctic algae can be considered as free of direct contamination from anthropogenic sources and due to the particular growing conditions imparted by the Antarctic environment, As speciation in these samples could be significantly different from algae studied to date. The As species were efficiently extracted from Antarctic algae samples by using a methanol:water (50:50) solution in an ultrasound bath for 120 min. The extraction efficiency of As species expressed as percentages of total element content were obtained in this work for the different algae samples studied. Chromatographic methods involving anion-exchange separation and using several elution gradients with a mobile phase containing ammonium carbonate at pH 10.0 were carefully developed and evaluated.  The use of a volatile compound such as, ammonium carbonate in the mobile phase allowed both pH adjustment and help avoiding salt deposition on the ICP-MS cones. Moreover, volatilization of this buffer was easily achieved for ES-ion trap MS analysis leading to an elevated signal-to-noise ratio. Additionally, a comparative As speciation study by analyzing other commonly found algae samples was performed. Speciation analysis of As in Antarctic algae showed a particular distribution of As among few chromatographic peaks. These results suggest a different distribution of As in Antarctic algae as compared to commercially available algae samples.