The determination of certain major and minor elements in geological samples by inductively coupled plasma atomic emission spectrometry. Some interference problems with the analysis of geological standard reference materials and nutrition supplements

Direct ICP-AES measurements of the digested geological standard reference m aterial samples yielded the wrong information about their composition. The differences between certified and measured concentrations of the samples we re due to the complicated sample matrix. The measured concentrations can be successfully corrected by using a multiple linear regression technique. Th e correction is based on the multiple regression line calculated from the a nalytical results at synthetic mixtures of matrix elements, where concentra tions varied on five levels. There were no significant (P = 0.05) differenc es between certified and measured concentrations in standard reference mate rials after the correction. The same method was used in the analysis of nut rition supplements.