Development of analytical methods for determination of trace elements in marine plankton by atomic absorption and inductively coupled plasma mass spectrometry
The objective of this study was to develop analytical: methods for the determination of trace elements in artificially grown marine plankton samples to provide a knowledge of metal concentrations in marine plankton. Samples were dissolved in a mixture of HF and HNO3 acids either in teflon beakers on a hot plate or in sealed vessels in a microwave oven. In flame atomic absorption spectrometric determinations (FAAS), it was necessary to complex fluoride with boric acid to prevent the precipitation of lanthanum fluoride. For the determination of calcium in air-acetylene flame, silicon had to be removed by heating to dryness, while for that of strontium the use of nitrous oxide-acetylene flame was essential. Lead was determined by hydride generation FAAS. Plumbane was trapped on the interior of a slotted quartz tube under fuel-lean conditions followed by atomization with the introduction of isobutylmethyl ketone. Although the detection limit was considerably improved, it was not linear with increasing trapping period due to the impurities in the reagents. A method was developed for total elemental characterization of marine plankton samples by inductively coupled plasma mass spectrometry (ICP-MS). Matrix induced signal suppressions were corrected by internal standardization. The method was applied to the analysis of plankton samples including several whose growth media had been enriched with selenium. The plankton samples were able to tolerate higher mercury concentrations as the selenium concentration increased. The effect of sodium on removal of silicon by heating to dryness was investigated. Evaporation as SiF4 was unsuccessful in the presence of sodium due the precipitation as sodium fluosilicate. Thus, sodium fluosilicate was first precipitated in acidic solution followed by extractions with mixtures of methanol/nitric acid to recover elements. Fourteen elements were determined accurately by ICP-MS with successful elimination of silicon. A gas chromatographic resin, Chromosorb 102, was investigated for on-line preconcentration of trace elements in seawater for determination by ICP-MS. Preconcentrations were achieved at pH 8.2 without any chelating agent followed by elution with dilute HNO3. The resin was capable of retaining 20 elements simultaneously in seawater. No significant degradation was observed in the long-term stability under acid-base treatment
