Application of the Enzyme Thermistor for Determination of Mercury and Other Heavy Metals Using Free and Immobilised Alcohol Oxidase

Abstract

This paper describes an enzymatic procedure for determination of mercury (I) and (II) based on the reversible competitive inhibition of free and immobilised alcohol oxidase Free enzyme was used in combination with immobilised catalase on controlled pore glass (CPG) coupled to a thermometric continous-flow system. Alcohol oxidase and methanol were injected into the system to give a temperature change corresponding to 100% enzyme activity. After inhibition by mercury, the enzyme activity and the corresponding temperature change were reduced. In order to improve the sensitivity, reusability and reduction of analysis time the alcohol oxidase was coimmobilised with catalase. Using free alcohol oxidase Mercury(II) was detected in the wide range between 25-1000 ng ml-1 with the linearity between 25 - 600 ng ml-1, and with the detection limit 5 ng ml-1 and the relative standard deviation RSD  2.7%,. While using immobilised enzyme 17 times improvement in detection range (1-60 ng ml-1), linearity (1 to 40 ng ml-1) and 10 times better detection limit (0.5 ng ml-1) with RSD  1.2 % has been achieved. Detection by mercury(II) can be overlap by Ag(I) present in ng ml-1 range.