Determination of heterocyclic amines in flame‐grilled fish patty by capillary electrophoresis

Abstract

A simple and reliable capillary zone electrophoretic (CZE) method for quantifying mutagenic and carcinogenic heterocyclic amines (HCAs) in cooked foods with UV‐visible diode‐array detection is described. The buffer system consisted of 50 mM disodium hydrogen phosphate, 30 mM sodium chloride, 20 mM citric acid and 26% methanol at pH 2.1. An uncoated silica tubing, 51 cm in length, was used for the CZE separation. The capillary tubing temperature was maintained at 25°C with a constant voltage of 20 kV. The reproducibility of the method was over 95% for a five‐replicate analysis of 10 μg/l‐spiked 2‐amino‐3,4,7,8‐tetramethylimidazo[4,5‐f]quinoxaline (4,7,8‐TriMeIQx) and the detection limit was in the low μg/l range with coefficients of variation between 6 and 18%. An analytical run took only 15 min for 12 known HCAs. Using this procedure, up to 30 samples could be analysed in a single day. The method is reliable and can be used for screening of various HCAs. It has been applied to assess the concentrations of heterocyclic amines in otak‐otak a Malay‐style grilled fish patty. The major mutagenic contaminant found in this foodstuff was 2‐aminodipyrido[1,2‐α:3',2'‐d]imidazole (Glu‐P‐2) (286–1068 μg/kg), followed by 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) (1.6–13.0 μg/kg) and 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ) (14.0–87.5 μg/kg). Two co‐mutagens norharman (NH) and harman (H) were also detected in otak‐otak at levels of 2.0–13.0 μg/kg and 12.8–21.3 μg/kg, respectively. The substantial amount of Glu‐P‐2 detected in otak‐otak is probably a result of the ingredients used and the high temperature grilling process.

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