METHANOL AND FORMALDEHYDE DETERMINATION B Y COLORIMETRY USING ALCOHOLOXIDASE

Recently, methanol has attracted attention as a clean alternative fuel . However, methanol is toxic and the formaldehyde formed during incomp lete combustion is even more toxic. Therefore, the development of an a ccurate determination method for methanol in the environment is very i mportant. However, it is difficult to analyze trace amounts of methano l in solution, especially in a sample solution containing formaldehyde . In the present method, methanol was oxidized to formaldehyde with al cohol oxidase (EC 1.1.3.13, AO), and the formaldehyde produced was det ermined by colorimetry. The sample containing methanol and formaldehyd e was bubbled with 100% oxygen for 15 min at a flow rate of 8.5 l/min. An aliquot of the sample was mixed with 0.1 ml of phosphate buffer so lution (pH 7.5, 1/15 M) and 0.25 unit AO, and was allowed to stand at 25 degrees C for 15 minutes. Formaldehyde was determined by colorimetr y with AHMT (4-amino-3-hydrazino-5-mercapto-1,2,4-triazole). In this m anner, total concentrations of formaldehyde and methanol could be dete rmined. On the other hand, only formaldehyde concentration could be de termined without AO. THus, the methanol concentration could be calcula ted from the difference between these two concentrations. The detectio n limit of the present method for methanol was 2.08 mu M, which was 14 times as sensitive as conventional colorimetry.