Biosensor for determination of carboxylic acids in wines based on the inhibition of sarcosine oxidase |
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Authors: | Jiri Zeravik Karel Lacina Milan Jilek Jiri Vlcek Petr Skládal |
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Institution: | 1. Department of Biochemistry, Masaryk University, Kotlá?ská 2, 611 37, Brno, Czech Republic 2. Department of Chemistry and Biochemistry, Mendel University, Zemědělská 1, 613 00, Brno, Czech Republic
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Abstract: | The flow-through amperometric biosensor is presented for determination of carboxylic acids. It is based on two sensor layers that are deposited on a platinum electrode. The inner layer serves to eliminate interferences by limiting diffusion of electrochemically active substances such as ascorbic acid. This layer is electro-polymerized using an equimolar mixture of o-phenylenediamine and resorcinol. The outer layer is prepared by cross-linking the enzyme sarcosine oxidase and bovine serum albumin using glutaraldehyde. The formation of enzymatically produced hydrogen peroxide is monitored at 600 mV vs. an Ag/AgCl reference electrode. The addition of carboxylic acids causes competitive inhibition of the enzyme and a decrease in signal. The assay was optimized for determination of carboxylic acids in wine samples. Following 10-fold dilution, most samples contain 1–10 mM individual carboxylic acids and thus a 5 mM concentration of sarcosine was chosen as being optimal for competition. In case of real samples, the biosensor measures the sum of all carboxylic acids, which serves as a parameter describing the quality of wines. Results from testing several wine samples are reported. |
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