Butterfly pea (Clitoria ternatea) extract as a green analytical tool for selective colorimetric detection of bisulphate (HSO4−) ion in aqueous medium

The blue color of butterfly pea (Clitoria ternatea) was extracted by Milli-Q water and evaluated for selective detection of bisulphate (HSO4−) ions. The stability of the Clitoria ternatea extract was established by UV–visible and fluorescence techniques. The blue water extract from Clitoria ternatea selectively recognizes HSO4− ions over various anions via a distinct visual color change from blue to purple with a significant hypsochromic shift of 68 nm in the UV–visible absorption spectra. Thus Clitoria ternatea extract provides a selective real time colorimetric monitoring of HSO4− ions which would pave the way for the development of low cost green analytical tool. This type of detection technique enhances the environmental and economic benefits and can emerge as an alternative form of synthetic chelating sensors.