Classifying wine according to geographical origin via quadrupole-based ICP-mass spectrometry measurements of boron isotope ratios.

The potential of quadrupole-based ICP-MS as a tool for B-isotopic analysis of wines and its usefulness in provenance determinations were assessed. A precision of 0.1-0.25% RSD (corresponding to a relative standard deviation of the mean of three replicate measurements of 0.06-0.12%) was sufficient to establish small differences in the B isotope ratios in wines from different geographical origins. Each sample measurement was bracketed by measurements of a standard and mass bias drift correction made by interpolation. Sample preparation was kept to a minimum to avoid possible fractionation. Dilution of the wine samples by a factor of 100 with 0.65% HNO3 was found to reduce matrix-induced mass discrimination substantially. Wines from three wine-producing regions, Stellenbosch, Robertson, and Swartland, in the Western Cape Province of South Africa, and wines from specific regions in France (Bergerac) and Italy (Valpolicella) were analyzed by ICP-QMS for their B-isotopic compositions. It was concluded that the 11B/10B ratios can be used to characterize wines from different geographical origins. Average 11B/10B ratios in red wines from South Africa (Stellenbosch), France (Bergerac), and Italy (Valpolicella) were found to differ by between 0.5 and 1.5%.

Multi-element analysis of South African wines by ICP-MS and their classification according to geographical origin.

Wines from three important wine-producing regions, Stellenbosch, Robertson, and Swartland, in the Western Cape Province of South Africa, were analyzed by ICP-MS and the elemental composition used in multivariate statistical analysis to classify the wines according to geographical origin. The method is based on the assumption that the provenance soil is an important contributor to the trace element composition of a wine. A total of 40 elements were determined in 40 wines. Of these, 20 elements: Li, B, Mg, Al, Si, Cl, Sc, Mn, Ni, Ga, Se, Rb, Sr, Nb, Cs, Ba, La, W, Tl, and U showed differences in their means across the three areas. In a stepwise discriminant analysis procedure, functions based on linear combinations of the log-transformed element concentrations of Al, Mn, Rb, Ba, W, and Tl were generated to correctly classify wines from each region. In an alternative approach, a pairwise discriminant analysis procedure, not previously used in wine provenance studies, was tested. In this procedure, the classification was done in three steps, with each step classifying a wine as coming from a certain region or not. The combination of elements characterizing wines from a particular region was different in each region. The discriminant functions were based on the following elements: Al, Mn, Rb, Ba, and W for Stellenbosch; Se, Rb, Cs, and Tl for Robertson; and Al, Mn, Rb, Sr, Ba, and Tl for Swartland. After this procedure, the classification of the wines into one of the groups was 100% successful.