Multi-elemental fingerprinting of plant tissue by semi-quantitative ICP-MS and chemometrics

The multi-elemental capacity of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is rarely fully utilized in traditional full-quantitative analysis. The main obstacles are limited availability of multi-elemental standards and the need for time-consuming external calibrations. In this study, a novel semi-quantitative quadrupole ICP-MS based method for multi-elemental fingerprinting of plant tissue was developed as a high-throughput alternative to full-quantitative analysis. The main analytical objectives were low data acquisition time (<60 seconds), detailed coverage of the atomic mass range from Li-7 to U-238 and discrimination power similar to full-quantitative analysis based on chemometric data analysis. The method was tested on grains of different rice (Oryza sativa) genotypes. The semi-quantitative rice fingerprints consisted of 30 elements based on the limit of detections as inclusion criteria. Fourteen of these were determined with an accuracy >70%. In conjunction with chemometrics, the discrimination power of the semi-quantitative results was better than that of full-quantitative analysis. The superior discrimination power of semi- quantitative analysis was maintained, even when it was combined with a high-throughput digestion procedure, which represented a 5 fold reduction in analytical labour consumption. Thus, the large amount of elemental information obtained using semi-quantitative ICP-MS fully outweighed the lack of accuracy compared to full-quantitative analysis. For the first time it is demonstrated that semi-quantitative ICP-MS in combination with chemometrics provides a fast and powerful alternative to traditional full-quantitative ICP-MS. The method developed here constitutes a promising novel analytical tool, which has the potential to mature into a routine procedure for testing e.g. the authenticity and adulteration of food products.