ICP-MS DETERMINATION OF METAL CONTENT IN TOOTHPASTE SAMPLES AFTER APPROPRIATE INTERNAL STANDARD SELECTION

STEFANOVA, V.; KMETOV, V.; DOMINI, C.; ALMAGRO, B.; SÁNCHEZ, A.; CANALS, A.

Las Palmas de Gran Canaria

Congreso; III Congreso Ibérico de Espectroscopía. XIX Reunión Nacional de Espectroscopía; 2004

In this study, the applicability of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to toothpaste analysis will be carried out. Sample preparation by means of microwave acid digestion will be optimized. Fully quantitative analysis of As, Sr, Zr, Cd, In, Ce, Pb, Bi, and U using external calibration standards will be performed. From these elements a semi-quant response curve will be constructed and semi-quantitativeconcentrations of rare earth and minor elements will be obtained. Toothpaste matrix is composed mainly of easy ionizable elements which increases significantly the electron density in the plasma. This process decreases the degree of ionization of the analytesaffecting primarily to elements with higher ionization potential (IP), which results in an increase of the non-spectral interferences of these elements.1 Due to the sample matrix complexity, an internal standard (IS) selection based on ionization potential matchingbetween analyte and IS instead of mass closing will be considered. In order to cover the analytes IP range, three elements are proposed for internal standard: 89Y (6.38 eV), 74Ge (7.89 eV) and 128Te (9.01 eV). This approach will be evaluated according to recoveriespercentages of standard additions in real samples. Results of metal content in differentsamples will be shown.1I. Rodushkin, T. Ruth and D. Klockare, J. Anal. At. Spectrom., 13, 159-156 (1998).Acknowledgements: Authors thank the Spanish Government for the financial support (projects reference:DPI2002-04305-C02-01 and PTR1995-0581-OP-02-01). Besides, B.A. wants to thank the fellowshipassociated to these projects and V.S. also thanks to the UA for the financial support of her visit.