Self-Colorimetric Determination of Bio-Ethanol Using Permanganate in Fermentation Samples

Without the aid of chromatographic techniques, quantification of bio-ethanol in fermentation-broth distillate becomes inconvenient. Potassium permanganate is preferable over potassium dichromate because of the latter well-known toxic properties, it is common used in ethyl alcohol determination either by visible determination of Cr(III) green optical density, a consumed Cr(VI) determination or the unreacted Cr(VI) determination iodometrically after alcohol oxidation. Nevertheless, these titre methods arise difficulties in experience analysts from multiple solutions preparation, standardization that should be carried out every day to successful end point detection in the presence of Cr(III) green color which leads to a significant ethanol quantification error. Noteworthy permanganate-iodometry drawbacks as same as titre dichromate of difficult practical procedures and multiple reagents employed. In this laboratory, a self colorimetric method is developed in neutral medium as alcohol-specific oxidizing agent precludes both of its undesirable high oxidizing properties and difficult titrimetric methodologies for bio-ethanol quantification and application of Beer-lambert law at high substrate concentrations. It is based on unreacted permanganate optical density difference between a non-ethanol-containing sample as a blank and ethanol-containing sample is directly proportional to the consumed permanganate amount in ethanol red-ox reaction and consequently directly proportional to ethanol content. This optical density difference versus ethanol concentration 1% - 6% v/v obeys Beer-Lambert law which provides limit of detection, limit of quantification and correlation coefficient equal 0.17%, 0.56% and 0.999 respectively.