SELECTIVE FLOW-INJECTION DETERMINATION OF METHANOL USING IMMOBILIZED ENZYME REACTORS

A flow-injection procedure is described for the determination of metha nol based on its alcohol oxidase-catalysed conversion to formaldehyde, which is then oxidized to formic acid by NAD(+) in the presence of fo rmaldehyde dehydrogenase. The concentration of NADH produced is measur ed by fluorimetry. Both enzymes and catalase, which is added to improv e enzyme stability and the extent of the overall enzymatic reaction, a re immobilized or coimmobilized on controlled-pore glass. Concentratio ns of methanol greater than or equal to 1.2 X 10(-6) M can be analysed . The proposed procedure has a linear application range of 4.0 X 10(-6 )-8.0 X 10(-5) M (fluorescence = -3.81 +/- 1.67 x 10(6) [methanol]; r = 0.998, n = 6), an R.S.D. of 1.8% at 2.4 X 10(-5) M methanol, and a s ampling frequency of 30 h(-1). Enzyme reactors keep their catalytic pr operties for 3-4 months and can be reused for 400 determinations on av erage.