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 d econtamination, labware precleaning, standards and samples storage and transportation, and final analytical measurements are discussed in te rms of getting unbiased accurate data. The potentialities of Pd and Ir matrix modifiers for the determination of femtogram contents of Bi we re examined. The Ir modifier provided better limit of detection for re al ice samples (0.15 pg ml(-1)) because of its higher purity and therm al 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 (th e period of the activity of Laki volcano in Iceland) and in the sectio ns of deep ice core, dated to Last Glacial Maximum (LGM)-Holocene tran sition (Bi content ranges within 0.3-0.7 pg ml(-1)). (C) 1997 Elsevier Science B.V.