A new ICP-MS method for the determination of iodine in food samples is presented. The method makes use of a new miniature cyclonic spray chamber and a concentric glass nebulizer that is designed for low sample uptakes and is operated in a self-aspirating mode. As a consequence the wash-out was accelerated over conventional systems. This configuration allows the direct determination of iodine in mineralized solutions following digestion with nitric acid only. No strong oxidizing reagents such as perchloric acid or lengthy sample preparation were necessary to alter the chemical form of potentially volatile species. The isotope dilution technique using the long-lived isotope 129I was applied to obtain freedom from matrix effects. The present study reports on results for total iodine in selected nutritional and biological reference materials and makes a comparison with instrumental neutron activation analysis.

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Inspired by the original work of Todolı ´et al. in designing a torch integrated sample introduction system (TISIS) for ICP-AES, the authors have modified this design for use with ICP-MS. A microflow concentric nebuliser has been coupled with a single pass low volume spray chamber that can be clipped directly onto the base of a standard ICP-MS torch. The memory effects are very low: a 10 mg l 21 tune solution containing Co, Ce and Tl was found to have washed out within 4 s. Matrix effects were reduced significantly across the mass range for a 10-fold diluted sea-water sample, with the signal being suppressed by only 10-20% compared with the response in ultra-pure water; detection limits were found to be higher than with the normal set up, with the instrument tuned to ''robust'' conditions. Finally, it was shown that the low dead volume and low flow rate meant that transient signals could be acquired easily, by flow injecting 100 ml of a standard and obtaining a flat topped peak with a 50 s signal plateau.

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