A Colorimetric Chemosensor Based on Alizarin Red for the Selective and Visual Detection of Cysteine in Aqueous and Real Samples

Organic dye-based colorimetric sensing has emerged as a rapid, cost-effective, and easily quantifiable technique for the detection of biologically relevant analytes. Herein, we describe a novel colorimetric sensor, based on Alizarin Red (AR), an anthraquinone pH indicator dye, for cysteine (Cys) selective detection, a thiol-containing amino acid that plays a key role in numerous physiological processes. Upon reaction with Cys, the AR dye displays typical spectral changes and coloration from yellow to pink that can be observed, making qualitative as well as quantitative detection possible. UV-Vis spectrophotometric titration revealed a sharp rise in absorbance at ۵۲۵ nm for rising Cys concentration with linearity in the range of ۱-۱۱ μM. A Benesi-Hildebrand plot established ۱:۱ binding stoichiometry between Cys and AR, and selectivity investigations demonstrated minimal interference from other common amino acids like methionine and glutamic acid. The sensor was also validated in real sample analysis employing a cysteine supplement with recovery ranging from ۹۷% to ۱۰۳%. These results confirm that the AR-based chemosensor is selective, sensitive, and suitable for real-world application in clinical diagnostics, pharmaceutical analysis, or environmental monitoring.

کلیدواژه ها:

Colorimetric sensor ، Cysteine detection ، Alizarin Red ، UV-Vis spectroscopy ، Selectivity ، Benesi-Hildebrand plot ، Real sample analysis ، Thiol sensing