Abstract
An amperometric bioelectrode for primary alcohols based on the incorporation of yeasts into the carbon paste matrix is reported. The response is based on the activity of alcohol dehydrogenase in yeasts. The intimate contact between the biocatalytic and sensing sites results in short response times. The addition of a redox-mediating hexacyanoferrate (III) ion greatly facilitates the detection of the enzymatically produced NADH. The effects of operating potential, carbon paste composition, concentration of coenzyme or redox mediator and other parameters are explored for optimum analytical performance. The dynamic properties of this electrode are exploited for detection in flow-injection systems, with a detection limit of 2 × 10 −6 M (9 ng) of ethanol. The relative standard deviation for repetitive injections of a 1× 10 −3 M ethanol solution over a 100-min period is 2.8%. Applicability to alcoholic beverages is illustrated. The trend in sensitivity toward different alcohols is in agreement with the known biospecificity of yeast alcohol dehydrogenase.
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