Quantification of N-methyl morpholine N-oxide in biorefinery process solution by headspace gas chromatography

Abstract This work developed a novel method for the determination of N-methyl morpholine N-oxide (NMMO) in the solution of biorefining, such as lyocell or biomass pretreatment. Copper hydride in situ (CuH) was generated in alkaline solution from sodium borohydride and cupric ion to completely reduce NMMO to N-methyl morpholine (NMM). Finally, the generated volatile NMM was analyzed by headspace gas chromatography. The generation of in situ CuH, complete reduction of NMMO, and the gas–liquid equilibration of NMM can be synchronously completed at 80 °C in 30 min, with a cupric ion concentration of 20 μmol, sodium hydroxide (0.8 mmol), sodium borohydride (3.0 mg), and 1.0 mL 30% ammonium hydroxide in 5.0 mL aqueous solution. The lowest limit of NMMO quantification was 42 mg/L in the present method, with good precision (standard deviation = 5.62%) and accuracy (recoveries from 95.9 to 106%). The present method has high accuracy, sensitivity, and throughput. It should be a useful tool to determine the content of NMMO and allow optimize the cost efficiency. Graphic abstract