DEVELOPMENT OF A SIMPLE COLORIMETRIC SENSOR FOR THE DETECTION OF COPPER AND IRON METAL IONS

Abstract

This research was to develop a micro-scale sensor for Cu and Fe metal ions determination by using extracted anthocyanins in butterfly pea (Clitoria ternatea L.) which is used as a natural indicator based on the interaction between anthocyanin and metal ions to form a complex compound, caused a change in the absorbance by naked-eye detected color change. From the results, butterfly pea extracted had maintained the stability of absorption spectra by water solvent more than alcohol solvent. Anthocyanin extracted from butterfly pea reacted with Cu and Fe metal ions showed the most clearly change in color under 0.01% acetate buffer at pH 6 due to the number of protons increased in anthocyanin structure. As
a result, the absorbance was shifted to the lower wavelength and the color changed from dark blue to purple since the flavylium cation was formed. The addition of divalent metal ion group except carbonate ion showed small interference with the color of detection. The quantitative analysis results by using the solution sensor system agreed well with the atomic absorption spectrometry (AAS) analysis. In addition, the optimum conditions obtained from the solution system were applied to a paper-based sensor coated on the filter paper. It was found that the results of Cu and Fe metals ions analysis were consistent with the solution sensor with naked-eye detection. Moreover, the developed Cu and Fe metal ions sensor would save time, cost-effectiveness and environmental friendliness.