Determination of N-Methyl morpholine in biomass pretreatment solutions by the ammonia-assisted headspace gas chromatography

An ammonia-assisted headspace gas chromatography (HS-GC) method was developed to determine the N-methyl morpholine (NMM) concentration in biomass fractionation processes. The use of ammonia gas increased the detection sensitivity of NMM, and minimized the interfering effect of other substances during the analysis. Results showed that, by adding 1.5 mL ammonium hydroxide (28–30%, w/w) and a 0.125 mmol of sodium hydroxide into a 4.0 g of sample solution containing 43.3% N-methylmorpholine N-oxide (NMMO), the gas-liquid equilibration of NMM was obtained within 30 min at 80 °C. The optimum sample size and the NMMO content in the sample solutions were 6.0 g and 43.3%, respectively. The present method was proved to be of high precision (RSD = 4.33%), sensitivity (LOQ = 71.9 mg/kg), and with recovery accuracy of 96.0–102%. The present method was rapid, accurate, which will be a powerful tool to optimize the reaction conditions in NMMO-based biomass pretreatment process for enhancing the cost effectivity.