L-Malic acid biosensor for field-based evaluation of apple, potato and tomato horticultural produce

摘要

A screen-printed three-electrode amperometric biosensor incorporating malic enzyme for the measuremtn of L-milic acid in apple, potato and tomato horticultural samples has been developed. The working electrode contained 0.38 mU of immobilised enzyme and was fabricated using rhodinised carbon to facilitate NADPH oxidation at an operating potential of +300 mV vs. Ag/AgCl compared with > + 600 mV for bare carbon. The linear range of the sensor was 0.028 - 0.7 mM L-malic acid with relative standard deviations of 3.3-13.3%. When testing with real apple, potato and tomato samples, the sensor accuracy was within 13.7% of a standard commercially available photometric test kit. The sensor approach is cheap, simple to perform and fapid (6 min), requiring only buffer-electrolyte and a small sample volume.