Determination of heavy metals in polar snow and ice by laser excited atomic fluorescence spectrometry with electrothermal atomization in a graphite cup

The strategy of direct analysis at the femtogram level is exemplified by the determination of Bi traces in the sections of two Greenland ice cores by laser excited atomic fluorescence spectrometry (LEAFS). The importance of all stages of the analysis: field sampling, mechanical decontamination, labware precleaning, standards and samples storage and transportation, and final analytical measurements are discussed in terms of getting unbiased accurate data. The potentialities of Pd and Ir matrix modifiers for the determination of femtogram contents of Bi were examined. The Ir modifier provided better limit of detection for real ice samples (0.15 pg ml(-1)) because of its higher purity and thermal stability, The contents of Bi well above LOD (1.4 and 0.8 pg ml(-1)) were measured in two sections of ice core, dated to 1783-1784 AD (the period of the activity of Laki volcano in Iceland) and in the sections of deep ice core, dated to Last Glacial Maximum (LGM)-Holocene transition (Bi content ranges within 0.3-0.7 pg ml(-1)). (C) 1997 Elsevier Science B.V.