ETH 6022: an artificial enzyme? A comparison between enzymatic and chemical recognition for sensing ethanol

Routinely the quantification of ethanol in clinical chemistry and food chemistry is performed by enzymatic methods in addition to chemical methods. Liver and yeast alcohol:NAD⁺ oxidoreductase (ADH, EC. 1.1.1.1) and alcohol oxidase AOD (EC 1.1.3.13) are mainly applied for selective evaluations by different kinds of bioassay. Nevertheless, drawbacks of ethanol sensing make the evaluation of ethanol concentrations in alcoholic beverages by an optical sensor, in a concentration range between 0·7% and 40%, most attractive. The chemical recognition process is based on a lipophilic amide of trifluoroacetylaniline (ETH 6022) as a ligand for ethanol implanted in a solvent polymeric membrane. The interaction leads to a hypsochromic shift of the absorption band in the ultraviolet region (305 nm). The chemical reaction in the apolar environment of the optode membrane is reversible. The principle of this recognition process is compared to the enzymatic reaction of ADH. In both cases a highly electrophilic centre participates in the interaction between the hydroxy group of the alcohol and the ligand. The selectivity behaviour of the artificial recognition process may be tailored by the substituents of the aromatic trifluoroacetyl compound. The response characteristics of the optochemical sensors are compared.