A Simple Method for Measuring Methanol Content in Gas Field Wastewater

This paper focuses on the color reaction of chromotrope and formaldehyde, an oxidation product of methanol, with sulfuric acid as the medium, under the existence of phosphoric acid. The generated purple complexes have characteristic absorption peak at wavelength of 570 nm. This reaction principle is applicable to measurement of methanol content in gas field wastewater. It is found there is a linear relationship between methanol content and absorbance while methanol content is within the range of 1~99.0 mg/L. This method has added recovery rate of 97.8~104.5%, detection limit of 1.0 mg/L and relative standard deviation less than 2.9%. The match rate of test results, obtained by this method and gas chromatography respectively, is higher than 95.0%. It is a simple, rapid and accurate method for supervision and management of methanol-containing wastewater in gas fields.