Simple impedimetric sensor for rapid lipase activity quantification

A simple and rapid impedimetric sensor applicable for industrial lipase activity quantification was developed and characterized. It is based on the lipase catalyzed degradation by hydrolysis of a thin nanocomposite substrate sensitive layer deposited on a PCB stick electrode usable as disposable or regenerable. The sensitive layer degradation rate was evaluated by the impedance changes registration along time resulting from its thickness diminution applying a small amplitude AC voltage with a constant frequency. The AC current phase shift variations along the time caused by the impedance changes were registered as s sensor response. The sensor was characterized in terms of linear quantification range, LOD, precision and quantification time. The response time was found to be from 80 to 6 s for the linear concentration range from 0.99x10^-2 to 1.68 U.S.P. U mL^-1 with relative errors from 3.75% to 1.24% respectively and a LOD of 8x10^-3 U.S.P. U mL^-1. Finally, lipase spiked whey samples taken from milk industry were quantified and the results were validated by a titrimetric method revealing a good agreement (relative error less than 4.5%).