Application a colorimetric method for qualitative analysis of methanol

In spite of many usefulness and progressive application of methanol in today life and industry, the accidental or unawareness drinking of it in alcoholic drinks caused some problems in public health. Therefore, it seems, qualitative detection of methanol in concentrations more than permissible dose in such products is necessary. In this study, a new qualitative method with easy application based on chromotropic acid method has been suggested for detection of toxic dose of methanol in alcoholic drinks. After adding potassium permanganate (contaning orthophosphoric acid) to sample into a fixed 50 mL volumetric flask in a cold bath and waiting for specified period, enough sodium hydrogen sulfite is added to it for decolorizing of mixture. Then, chromotropic acid with concentrated sulfuric is added to the flask and it is fixed in a 60°C bath for 15 minutes. After this time, the flask is cooled and its volume is arisen to 50 mL and then, optical density of the solution is determined in 575 nm. The obtained results were shown; application of micro amounts of sample and reactants would have good results such as decreasing of application limits of classic chromotropic acid method. Furthermore, using of a competitive reactant (propanol) is lead to detection of methanol in concentrations more than toxic amount in alcoholic drinks. For detection of methanol in concentrations more than permissible dose or toxic amount in alcoholic drinks that based on European countries standard is about 0.4% v/v, the chromotropic acid method can be used as an accurate, sensitive, simple, cheap and rapid method in general laboratories with no especial equipment.