Qualitative identification of metal ions in honey by two-dimensional thin-layer chromatography

Abstract

Two-dimensional thin-layer chromatography (2D TLC) has been used as a screening method for detection of the metal ions Al 3+ , Cr 3+ , Cu 2+ , Ni 2+ , Mg 2+ , Zn 2+ , Mn 2+ , Pb 2+ , Sn(IV), and Fe 3+ in honey. Different mobile phases and visualization reagents were tested. The best separation was achieved on precoated microcrystalline cellulose TLC plates with acetonitrile-HCl-water, 73 + 15 + 12 ( v/v ), as mobile phase in the direction x , and 2-pentanol-acetonitrile-HCl, 30 + 20 + 50 ( v/v ), in the direction y . A mixture of quercetin, dimethylglyoxime, and NH 3 was used for visualization of the chromatographic spots. This reagent mixture produced intensely colored spots for all the ions tested and enabled their identification at concentrations ranging from 50 to 1000 ng per spot.The method was used to identify metal ions in honey samples, dissolved in 2 mol L −1 hydrochloric acid, after microwave digestion. Seven metal ions, Al 3+ , Cr 3+ , Fe 3+ , Mn 2+ , Pb 2+ , Ni 2+ and Sn(IV), were identified.