Quantitative analysis of methanol in wastewater by GC-MS with direct injection or headspace SPME sample introduction

Abstract

Monitoring methanol (MeOH) concentration in wastewater treatment processes is important because methanol is a widely used carbon source for denitrification. Headspace solid-phase microextraction (HS-SPME) and direct liquid injection coupled with gas chromatography and mass spectrometry (GC/MS) were studied to analyze methanol in municipal wastewater samples in the μg mL⁻¹ range. The conditions applied for both methods are presented. The extraction parameters for the HS-SPME method, such as SPME fiber selection, extraction temperature and time, agitation, pH value of the solution, and salt effect, were investigated. For the liquid injection method, the critical parameter was to select a polar column, the DB-WAX capillary column. Linear calibration curves were obtained over 3 orders of magnitude using methanol-d₃ (MeOH-d₃) or acetonitrile (ACN) as an internal standard. Both methods were validated with repeatability and recovery experiments. The liquid injection method requires a smaller injection volume and allows for faster analysis and better precision. The HS-SPME method also has reliable performance with less than 10% error. In addition, the comparison of the two methods on practical applications and maintenance is included.