Novel Gas Chromatography–Mass Spectrometry Methods for Characterization of Volatile Organic Compounds and Water in Fast Pyrolysis Liquids

A novel method for the analysis of volatile organic compounds (VOCs) in fast pyrolysis liquids has been developed. Using a full evaporation technique (FET), the total concentrations of major volatiles in old and fresh biocrude oil (BCO) samples ranged between 0.71 and 2.42 wt %. Formaldehyde, methanol, methyl formate, and acetic acid methyl ester (AAM) were the dominant VOCs across all samples. The results revealed that concentrations and types of VOCs in BCOs largely depend upon their feedstock type and storage period. After 24 months, only a quarter of the initial formaldehyde concentration in beech-derived BCO was left, whereas the amount of AAM doubled within the same period. Make-up additives, such as methanol, ethanol, or isopropyl alcohol, often used to homogenize BCO products, were detected in BCOs obtained from commercial and semi-commercial production. Good reproducibility and high correlation of analytical responses of various calibration standards used in the quantitative evaluation of the VOCs illustrate the suitability of a FET-headspace for the analysis of VOCs in BCO samples. There was a close concordance between BCO water contents analytically determined by gas chromatography–mass spectrometry analysis and Karl Fischer titration, an indication of the former suitability as an alternative.