Advantages and limitations of the semi-quantitative operation mode of an inductively coupled plasma-mass spectrometer for multi-element analysis of wines Original Research Article

The suitability of the semi-quantitative mode of analysis of a Perkin-Elmer inductively coupled plasma quadrupole-mass spectrometer for multi-element characterization of fortified and table wines was tested. The samples, embracing red and white table, and Port wines, were first submitted to an UV-irradiation pre-treatment. The same samples were analysed, in parallel, by using the quantitative mode of the same equipment, and the results were compared. External calibration with aqueous standards was used in the quantitative mode and calibration with only one aqueous multi-element standard was used in the semi-quantitative mode. Thirty elements, including major, minor and trace elements (Al, Ba, Cd, Co, Cr, Cu, Fe, Ga, Li, Mn, Ni, Pb, Rb, Sr, V, Zn and the rare earth elements (REEs) La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were measured by the two modes of analysis. For most elements the semi-quantitative mode provided two to six times higher limits of detection than those obtained by the quantitative mode. The precision of the results were similar for both modes, with relative standards deviation between 0.5 and 5%, in many cases. Comparable values of concentration (differences <20%) were obtained by the two methodologies, except for Cd, Ga, Li and the REEs. A linear least-squares adjustment of the two global sets of results (semi-quantitative mode (y-axis) versus quantitative mode (x-axis)) yielded the equation: y=(0.93±0.01)x+(1±11) with a very high correlation coefficient of 0.9992 (n=40). Although the results obtained by the semi-quantitative mode were, on average, slightly lower than those given by the quantitative mode (slope <1), semi-quantitative analysis can be an important tool for comparison of elemental compositions of wines, including fortified wines. It gives rapid information about the concentration levels of a large number of elements, and presents some economic advantages relatively to the quantitative mode: it is faster and requires fewer reagents.