Selective application of two rapid, low-cost electrochemical methods to quantify glycerol according to the sample nature

Abstract

The selection of the method to quantify glycerol largely depends on the amount present in the sample, the matrix nature where glycerol has to be determined, and the potential interferences accompanying the analyte. We compared different electrochemical methods to determine glycerol in terms of convenience, from the point of view of the sample nature, the time spent to accomplish the analysis, the preferably use of green consumables, the limit of detection (LD), and the operational cost. We studied two alternative methodologies based on amperometric measurements to determine glycerol. In aqueous media, we use the versatile gold electrode, being the linear range 2.5 × 10−5 to 2.0 × 10−3 M, and the LD 10 μM (3 × SDb, standard deviation of the blank). In extremely complex matrixes, where many electroactive species are expected to be present, we propose to use a new approach based on biosensor technology, which takes advantage of an inexpensive, soluble redox mediator, and uses only one enzyme with its cofactor in solution. The substrate was a glassy carbon paste electrode; the system used the enzyme glycerol dehydrogenase, soluble NAD+ as cofactor, and ferricyanide as charge mediator. The response showed to be linear between 7.0 × 10−5 and 1.8 × 10−3 M, and the LD was 20 μM. The biosensor displayed more than two month stability without the enzyme losing activity when kept dried at 4 °C. The time taken to complete the analysis was 10 min, counting from the moment the sample was taken until the signal was recorded. The operational cost of the whole analysis was less than that derived of using other biosensors or a spectrophotometric assay.