Interlaboratory Study of Sample Homogeneity Impact on CHNS, Water, and ICP Analysis of Biomass Liquefaction Oils

Five biomass liquefaction oils (BLOs) comprising four different lignocellulosic fast pyrolysis bio-oils (FPBO) and one algae-derived hydrothermal liquefaction (HTL) biocrude were subject to an interlaboratory study (ILS). Participating laboratories were asked to analyze all BLOs after gentle sample mixing and again but with vigorous mixing. Blind duplicates were included to improve the statistical power. Requested analysis included CHN, water, trace nitrogen, and sulfur (using solvent-miscible solvents) and ICP by an independently developed method. Blind duplicates applied in this study indicated that representative sampling was achieved to the extent required for bulk composition analysis. More vigorous sample mixing did not yield benefits for precision or reproducibility for composition analysis; however, the importance of consistent and precise sample mixing is underscored. Results of CHN and water showed performance similar to those of previous studies. However, adapted trace nitrogen methods consistently report 25–50% lower nitrogen content compared to ASTM D5291 and highlight the need for reconciliation. Poor performance of ICP across eight participant laboratories further underscores the need for standardization. ICP sample preparation by dissolution is generally ineffective for the recovery of more recalcitrant multivalent analytes. Digestion is recommended as the sample preparation of choice for ICP analysis of BLOs.