Development of Rapid Colorimetric Assay for Detection of Gluconic Acid Using Iron(II) and Indigo Carmine

In this work, a simple and rapid spectrophotometric method, which is based on the fact that Iron(II)-gluconic acid complex as a kind of reducing agent deterioration of indigo carmine dyes, was developed to detect gluconic acid in food. Under the optimal experimental condition, a linear range of 3.6 mu M to 900 mu M was obtained for gluconic acid with a limit of detection of 1.1 mu M. The colorimetric method was rapid and robust with a low cost and can be applied to gluconic acid detection in food samples.