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 material samples yielded the wrong information about their composition. The differences between certified and measured concentrations of the samples were due to the complicated sample matrix. The measured concentrations can be successfully corrected by using a multiple linear regression technique. The correction is based on the multiple regression line calculated from the analytical results at synthetic mixtures of matrix elements, where concentrations varied on five levels. There were no significant (P = 0.05) differences between certified and measured concentrations in standard reference materials after the correction. The same method was used in the analysis of nutrition supplements.