Determination of Trace Metals in Garlic Bulbs (Allium sativum L.): A Variety Discrimination by Inductively Coupled Plasma Mass Spectrometry

Abstract

Thirteen trace metals (Li, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Nb, and Mo) and two toxic metals (Cd and Pb) in two kinds of garlic bulbs have been quantified. Following the dehydration process, the garlic residues are digested using 10.0 mL of an acid mixture of HNO3:H2O2:HCl (3:1:1, v/v/v). The trace metal assay is accomplished by inductively coupled plasma mass spectrometry (ICP-MS). Results reveal that the metal levels for the garlic bulbs with purple skin in dry weight are 14.5, 1.32, 3.03, 3.88, 13.0, 2.50, 1.00, 64.1, 139.6, 13.6, 18.4, 0.29, 0.11, 1.60, and 0.52 mg/kg for Li, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Nb, Mo, Cd, and Pb, respectively, while the corresponding metal concentrations in the garlics with white skin are 22.9, 2.70, 3.95, 6.60, 19.7, 3.72, 1.16, 79.9, 149.8, 19.7, 24.0, 0.33, 0.43, 0.84, and 0.30 mg/kg, respectively. In general, the trace metals in both varieties are clearly under the FAO/WHO maximum permissible limits. However, it is observed that the garlics with white skin show higher quantities of essential/possible essential metals and lower levels of toxic metals, demonstrating the garlics with white skin exhibit a higher nutrition quality and are a better source of essential minerals.