Analysis of acrylamide in food products by in-line preconcentration capillary zone electrophoresis

Two in-line preconcentration capillary zone electrophoresis (CZE) methods (field amplified sample injection (FASI) and stacking with sample matrix removal (LVSS)) have been evaluated for the analysis of acrylamide (AA) in foodstuffs. To allow the determination of AA by CZE, it was derivatized using 2-mercaptobenzoic acid. For FASI, the optimum conditions were water at pH ≥ 10 adjusted with NH3 as sample solvent, 35 s hydrodynamic injection (0.5 psi) of a water plug, 35 s of electrokinetic injection (−10 kV) of the sample, and 6 s hydrodynamic injection (0.5 psi) of another water plug to prevent AA removal by EOF. In stacking with sample matrix removal, the reversal time was found to be around 3.3 min. A 40 mM phosphate buffer (pH 8.5) was used as carrier electrolyte for CZE separation in both cases. For both FASI and LVSS methods, linear calibration curves over the range studied (10–1000 μg L−1 and 25–1000 μg L−1, respectively), limit of detection (LOD) on standards (1 μg L−1 for FASI and 7 μg L−1 for LVSS), limit of detection on samples (3 ng g−1 for FASI and 20 ng g−1 for LVSS) and both run-to-run (up to 14% for concentration and 0.8% for time values) and day-to-day precisions (up to 16% and 5% for concentration and time values, respectively) were established. Due to the lower detection limits obtained with the FASI–CZE this method was applied to the analysis of AA in different foodstuffs such as biscuits, cereals, crisp bread, snacks and coffee, and the results were compared with those obtained by LC–MS/MS.