Development of sorbent modified with cyanidin from red cabbage extract for naked-eye determination of heavy metal ions

Abstract

This research aims to use a natural product as colorimetric reagent modified on solid sorbent for naked-eye determination of metal ions in term of both qualitative and quantitative analysis. Cyanidin from red cabbage was the best choice. The selectivity of this method was examined by considering of the pH of cyanidin solution operated together with masking agent. At first step, metal ion detection was studied by using cyanidin solution. It was found that Cu(II), Pb(II), Fe(III) and Al(III) clearly formed complexes with cyanidin. For simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III), cyanidin in the buffer solution at pH 7, 6, 5 and 4, respectively, were employed along with using 0.1 M KF, 1% w/v DMG and the mixture of 0.1 M KF and 1% w/v DMG as masking agents for Fe(III). Al(III) and Pb(II) determination, respectively. The lowest concentrations for naked-eye detection of Cu(II), Pb(II), Al(III) and Fe(III) were 50, 80, 50 and 200 µM, respectively. Next step, cyanidin was modified on Amberlite XAD-7 resin to be AXAD-7Cy. In this study, AXAD-7Cy coated with cyanidin in 0.6% v/v HCL/MeOH was appropriate sorbent. It was found that Cu(II), Pb(II), Al(III) and Fe(III) also contributed the color change on AXAD-7Cy. The simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III) was operated under buffer solution at pH 7, 6, 5 and 4, respectively, as the same results testing in cyanidin solution. 0.1 M thiourea and the mixture of 0.1 M thiourea and 0.1 M KF were used as masking agents for Al(III) and Pb(II) determination, respectively. The detection limit observed by naked-eye was 10, 200, 40 and 60 µM for Cu(II), Pb(II), Al(III) and Fe(III) analysis, respectively. Cyanidin in form of both solution and modified on AXAD-7 could be potentially applied in real water sample (tap and pond water). This developed method showed the potentially determined target metal ions at the micromolar level with simplicity, rapidity, low cost, no sample preparation requirement, and environmental friendly detection due to using low volume of all reagents