Simultaneous determination of twenty heterocyclic amines in cooking oil using dispersive solid phase extraction (QuEChERS) and high performance liquid chromatography-electrospray-tandem mass spectrometry

A commercial kit (QuEChERS) for dispersive solid phase extraction was used with HPLC-ESI-MS/MS analysis to determine concentrations of 20 heterocyclic amines (HAs) in 48 unrefined and refined cooking fats (number): lard (16); tallow (8), coconut oil (6); other solid fats (8); vegetable oils (10). The average suppression of ESI-MS response to HAs in extracts from cooking oil was 84%: 18 HAs were quantified from 0.02 to 1.2 pmol/g, using an internal standard and clean-matrix-matched calibration standards; Norharman and Harman were quantified from 0.02 to 5 pmol/g using external standards in solvent. Measurements of method performance in cooking oils spiked with 18 HAs were (averages for lard, tallow, coconut oil, respectively): intraday precision, 7%, 16%, 8%; interday precision, 18%, 18%, 13%; recovery 65%, 61%, 74%. Norharman (N) and Harman (H) were detected in 42 samples (88%), within and often above the quantitation range. Total concentrations were significantly higher in unrefined cooking oils than refined (>15X, P < 0.05). Average concentrations were (in unrefined lard, tallow and coconut oil respectively): Norharman, 46, 21, 41 pmol/g; Harman 72, 54, 25 pmol/g. Other HAs were detected (rarely; with Norharman and Harman in the unrefined fats): Trp-P-2, 0.1 pmol/g (6); Trp-P-1, 0.4 pmol/g (1); AαC, 0.3 pmol/g (1).