Abstract:
<p align="justify"> A highly sensitive flow injection system was developed for the methanol determination. The system is based on the oxidation of methanol in the presence of alcohol oxidase to yield formaldehyde and hydrogen peroxide. The concentration of the hydrogen peroxide produced was determined by luminol chemiluminescence. A four-line flow injection assembly was used. The sample was injected into a flow of phosphate buffer at pH 9 that merged with a flow containing alcohol oxidase. The enzymatic reaction takes place in a coiled tube, 2 meters · long and 0.8 mm i.d. Just in front of the chemiluminescence cell, the flow containing the sample merged with a flow of luminol (1.5 mM) and potassium ferricyanide (20 mM). The injected volume was 50 pL and the total flow rate 1.6 mL min·1 The determination range was 5x10"4 -1x10'2 %(v/v) methanol. The throughput was 40 samples per hour. From 20 tested substances, only L-cysteine generated a signal comparable with that of methanol. The others, at concentrations equal to those of methanol, either gave no signal at all (n-butanol, cyclo-hexanol, glycine, L-threonine, L-proline, copper sulphate) or gave signals much smaller than that of methanol. </p>