Chemometric classification and discrimination of herbal dietary supplements based on ICP-MS elemental profiling

Abstract

This study presents the determination of elemental profiling of representative dietary herbal supplements which were purchased on the Croatian market in the forms of capsules, powders, jams or liquids. Using inductively coupled plasma mass spectrometry (ICP-MS), twenty-four elements in eighty-seven different samples were determined. Electrothermal atomic absorption with hydride generation technique (HG-ETAAS) applied for the selenium determination in all samples gave the similar results as ICP-MS technique. Elemental profiling resulted with determination of major constituents Na, Mg, Ka and Ca with mean concentration values of 2900, 2700, 9200, and 16,600 mg kg−1, respectively. Elements of middle concentration range were: B, Al, Mn, Fe, Zn and Sr (31.8–1050 mg kg−1). Trace and ultra-trace levels comprise of Se, V, Cr, Co, Ni, Cu, As, Mo, Cd, Sb, Hg, Tl and Pb (21.7–11,300 µg kg−1). Using PLS-DA statistical analysis, the elements Se, Na, Fe, Co, Tl, and Zn, were established as the marker elements with the greatest discriminating power between supplement samples. Multivariate PCA analysis resulted with the successful discrimination of Se and Zn enriched supplements. Hierarchical cluster analysis (HCA) enhanced the recognition of similarities in sub-clusters of samples. Minor discrepancies in trace and ultra-trace elemental profiles revealed Hg, As, Cd, Pb, Cr and Co as the key elements for discrimination between two groups of Ayurvedic and spirulina-based supplements. The HCA method also allowed visualization of the exceptional elemental profile of several mixed-herb supplements. There were distinctive features of herbal dietary supplements with peculiar influences of botanical, environmental and/or production conditions on their elemental profile.