title: Using design of experiments to optimize derivatization with methyl chloroformate for quantitative analysis of the aqueous phase from hydrothermal liquefaction of biomass.
abstract: Hydrothermal liquefaction is a promising technique for the production of bio-oil. The process produces an oil phase, a gas phase, a solid residue, and an aqueous phase. Gas chromatography coupled with mass spectrometry is used to analyze the complex aqueous phase. Especially small organic acids and nitrogen-containing compounds are of interest. The efficient derivatization reagent methyl chloroformate was used to make analysis of the complex aqueous phase from hydrothermal liquefaction of dried distillers grains with solubles possible. A circumscribed central composite design was used to optimize the responses of both derivatized and nonderivatized analytes, which included small organic acids, pyrazines, phenol, and cyclic ketones. Response surface methodology was used to visualize significant factors and identify optimized derivatization conditions (volumes of methyl chloroformate, NaOH solution, methanol, and pyridine). Twenty-nine analytes of small organic acids, pyrazines, phenol, and cyclic ketones were quantified. An additional three analytes were pseudoquantified with use of standards with similar mass spectra. Calibration curves with high correlation coefficients were obtained, in most cases R (2)  > 0.991. Method validation was evaluated with repeatability, and spike recoveries of all 29 analytes were obtained. The 32 analytes were quantified in samples from the commissioning of a continuous flow reactor and in samples from recirculation experiments involving the aqueous phase. The results indicated when the steady-state condition of the flow reactor was obtained and the effects of recirculation. The validated method will be especially useful for investigations of the effect of small organic acids on the hydrothermal liquefaction process.
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: René Bjerregaard
authors.initials: RB
authors.lastname: Madsen
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Mads Mørk
authors.initials: MM
authors.lastname: Jensen
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Anders Juul
authors.initials: AJ
authors.lastname: Mørup
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Kasper
authors.initials: K
authors.lastname: Houlberg
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Per Sigaard
authors.initials: PS
authors.lastname: Christensen
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Maika
authors.initials: M
authors.lastname: Klemmer
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Becker
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark.
authors.forename: Bo Brummerstedt
authors.initials: BB
authors.lastname: Iversen
authors.affiliation: Department of Chemistry and INANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark. glasius@chem.au.dk.
authors.forename: Marianne
authors.initials: M
authors.lastname: Glasius
mesh_terms: D056804:Biofuels / Q000032:analysis*; D018533:Biomass; D019149:Bioreactors; D057168:Distillation; D002523:Edible Grain / Q000737:chemistry*; D005561:Formates / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D013696:Temperature; D014867:Water / Q000032:analysis
chemical_list: D056804:Biofuels; D005561:Formates; D014867:Water; C014667:methyl chloroformate
keywords: Aqueous phase recirculation; Design of experiments; Hydrothermal liquefaction aqueous phase; Methyl chloroformate derivatization