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Abstract

A sensitive method for the simultaneous determination of 7Li, 27Al and 56Fe by cold plasma ICP-MS was developed and validated. Experimental design was used to investigate the effects of torch position, torch power, lens 2 voltage, and coolant flow. Regression models and desirability functions were applied to find the experimental conditions providing the highest global sensitivity in a multi-elemental analysis. Validation was performed in terms of limits of detection (LOD), limits of quantitation (LOQ), linearity and precision. LODs were 1.4 and 159 ng L−1 for 7Li and 56Fe, respectively; the highest LOD found being that for 27Al (425 ng L−1). Linear ranges of 5 orders of magnitude for Li and 3 orders for Fe were statistically verified for each compound. Precision was evaluated by testing two concentration levels, and good results in terms of both intra-day repeatability and intermediate precision were obtained. RSD values lower than 4.8% at the lowest concentration level were calculated for intra-day repeatability. Commercially available soft drinks and alcoholic beverages contained in different packaging materials (TetraPack®, polyethylene terephthalate (PET), commercial cans and glass) were analysed, and all the analytes were detected and quantitated. Copyright © 2002 John Wiley & Sons, Ltd.