The classification of agricultural products according to geographical origin by means of quadrupole-based ICP-mass spectrometry for the determination of ¹¹B/¹°B isotope ratios, and the study of boron isotope fractionation

M.Sc.The 11B/10B stable isotope ratio in wine- and provenance soil samples of four South African wine regions was determined by means of quadrupole inductively coupled plasma mass spectrometry (ICP-MS). The data obtained was combined with multi-element results for the same samples. Discriminant analysis and ANOVA statistics were utilized to create a footprint of wines compared to their provenance soil. The results showed that the stable boron isotope ratio was a distinguishable characteristic in wine and soil samples for the Stellenbosch, Robertson, Swartland, and Walker Bay wine regions. The potential improvement of precision and accuracy was investigated specifically for ICP-QMS (quadrupole mass spectrometry) analysis of boron isotope ratios. Sample preparation methods for the matrices used in this work were developed and applied. The influence of the matrix components was investigated. Ion exchange separation procedures were developed for the separation of total B from the wine and soil matrices. Results were treated mathematically to minimize mass bias effects. It was found that combined matrix effects and TDS (total dissolved solids) deposition did have a pronounced effect on the 11B/10B isotope ratios of the samples. The possibility of boron isotope fractionation was investigated in vine plants. Hydroponic experiments were set up with test plants of two cultivars. A 10B enriched nutrient solution or growth solution with natural 11B/10B ratio was supplied to the plants during alternating periods of 5 weeks each. New growth leaves were harvested once every week during each of these time periods. All samples were carefully prepared and analyzed to determine the relationship of the 11B/10B ratio in the leaves compared to that of the supplied nutrient solution. It was observed that the 11B/10B isotope ratio of the growth solution had an influence on the 11B/10B stable isotope ratio in new growth leaves of vine plants