Plasma alkylresorcinols are increasingly analyzed in cohort studies to improve estimates of whole grain intake and their relationship with disease incidence. Current methods require large volumes of solvent (>10 ml/sample) and have relatively low daily sample throughput. We tested five different supported extraction methods for extracting alkylresorcinols from plasma and improved a normal-phase liquid chromatography coupled to a tandem mass spectrometer method to reduce sample analysis time. The method was validated and compared with gas chromatography-mass spectrometry analysis. Sample preparation with HybridSPE supported extraction was most effective for alkylresorcinol extraction, with recoveries of 77-82% from 100 μl of plasma. The use of 96-well plates allowed extraction of 160 samples per day. Using a 5-cm NH2 column and heptane reduced run times to 3 min. The new method had a limit of detection and limit of quantification equivalent to 1.1-1.8 nmol/L and 3.5-6.1 nmol/L plasma, respectively, for the different alkylresorcinol homologues. Accuracy was 93-105%, and intra- and inter-batch precision values were 4-18% across different plasma concentrations. This method makes it possible to quantify plasma alkylresorcinols in 100 μl of plasma at a rate of at least 160 samples per day without the need for large volumes of organic solvents.
Keywords: Alkylresorcinols; Biomarkers; Blood plasma; Liquid chromatography–tandem mass spectrometry; Whole grain.
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