Determination of the concentration of higher alcohols with enzyme coupled flow-injection analysis in model systems

The activities of native and immobilized alcohol oxidases (AOD) originating from Pichia pastoris, Hansenula sp., Candida boidinii and Peniophora gigantea were compared with regard to the oxidation of various higher alcohols. Except Candida boidinii, the immobilized enzymes were applied in a flow-injection analysis system and investigated as a function of the various operation variables. During the oxidation O2 is consumed which concentration was measured with an amperometric detector. At the same time H2O2 is produced, the concentration of which is used for the oxidation of a redox indicator (ABTS) catalysed by peroxidase and measured with a photometer. The amperometric method is simpler and more economical, but less sensitive. The photometric method consumes the dissolved redox indicator and peroxidase, but is highly sensitive especially for higher alcohols. The concentrations of n-propanol, n-butanol and n-pentanol can be measured with satisfactory sensitivity with immobilized alcohol oxidases originating from Pichia pastoris and Peniophera gigantea in a one molar potassium phosphate buffer (pH 7.5). The concentrations of isopropanol, octanol, dodecanol and benzylalcohol can be measured only when larger than 1 g l−1.