GNPS_GC_Derivatized human blood serum spiked with standards of FAMEs and hydrocarbons

Post-thawing, human serum samples (30 uL) were sequentially extracted using solvent extraction, once with 1 mL of acetonitrile: isopropanol: water (3:3:2, v/v) ratio , followed by another extraction with 500 uL of acetonitrile: water (1:1, v/v) ratio mixture at 4 C. Adonitol (Cat. No. A5502-5G, Sigma-Aldrich; 5 uL from a 10 mg/ml stock), an internal standard was added to all samples prior to solvent extraction. The pooled extracts (~ 1500 uL) resulting from the two steps were dried in vacuo at 4 C prior to chemical derivatization. Dummy extractions were performed in blank tubes that served as extraction blanks for background subtraction of noise resulting from extraction solvents, derivatization reagents, unwanted sources, and other sources of contamination from the analytical platform, i.e., septa, liner, column, vials, handling etc. All samples (i.e., except FAMEs and n-alkanes) were sequentially derivatized with methoxyamine hydrochloride (MeOX) and 1% TMCS in N-methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA).