Highly sensitive colorimetric determination of biothiols based on I−-H2O2-3,3’,5,5’-tetramethylbenzidine system

In this work, a simple, highly selective and sensitive method for detecting biothiols based on I − -H 2 O 2 -3,3’,5,5’-tetramethylbenzidine (TMB) system is developed. The main determination mechanism of the colorimetric assay is that iodide could catalyze the oxidation of TMB in the presence of H 2 O 2 to form oxidized TMB (ox-TMB). With the introduction of biothiols, the biothiols cause the reduction of ox-TMB, accompanied with the color of the solution changing from the original blue to colorlessness. UV–vis absorption spectrum shows that the intensity of peak at 652   nm reduces largely. Other 20 kinds of amino acids have also been studied for proving the high sensitivity and selectivity of current approach. This colorimetric analysis method can be successfully applied to the practical sample determination with satisfactory results. The results indicated that this work is a facile, time-saving and cost-effective method for detecting biothiols.