Effect of boiling and peeling on manganese content of some vegetables determined by derivative anodic stripping chronopotentiometry (dASCP)

The purpose of this paper was two-fold: to optimise an analytical method based on derivative anodic stripping chronopotentiometry (dASCP) for reliable trace manganese determination in different fresh vegetables and aromatic plants, and to use this technique to asses the effect of boiling and peeling processing on their manganese content. The deposition potential was −1700 mV and the deposition time 120 s; in this conditions the limits of detection 8.0 ng kg−1 (ppt) and the accuracy of the method, assessed using certified reference materials, was within 95.0%. Among the studied fresh vegetables, the highest content of manganese was found in vegetables with dark green leaves as chicory and spinach (respectively, 3.5 and 3.3 mg/100 g), while vegetables with light green leaves as lettuce, together with carrots, garlic and pore mushrooms had manganese levels lower than 1.0 mg/100 g. Boiling processing cause a significant decrease of manganese levels in artichokes, tomatoes, chicory, garlic, mushrooms, peeled carrots and potatoes, spinach, and string beans (p ⩽ 0.005, ANOVA). Fennels, lettuce, marrow, unpeeled carrots and unpeeled potatoes did not show any statistical significant changes after boiling. Also peeling significantly influenced the content of manganese of carrots and potatoes (p ⩽ 0.01, ANOVA) and favoured manganese loss during boiling.