Highly sensitive capillary isotachophoresis for simultaneous detection and quantification of synthetic food colourants in complex matrices

This study presents the analytical potential of capillary isotachophoresis (ITP) in spike mode, combined with selective photometric absorbance detection, for the determination of 11 synthetic food colourants in complex food matrices. The method employs β-cyclodextrin as a complexing agent, selectively modulating colourant mobilities behind typical food matrix macrocomponents. A systematic selection of spacing constituents enabled the resolution of eight colourants in a single ITP run. The photometric detector, operating at 405 and 580 nm, enhanced detection selectivity, achieving ultra-trace detection limits (250 ng/L–10 µg/L) with high reproducibility (RSD 1–5 %). Compared to chromatographic techniques, this approach offers a rapid, cost-effective, and environmentally friendly alternative with minimal sample preparation. Excellent agreement was observed between ITP and capillary zone electrophoresis quantification of food colourants in real samples, including soft drinks, fruit concentrates, liqueurs and alcoholic drinks, and chewing gums. This study demonstrates the potential of ITP as a high-throughput, ultra-sensitive technique for food quality control.