Response surface methodology for capillary electrochromatography and sample stacking in the analysis of food additive residues in environmental water samples

Abstract

Food additives (FAs) are defined by the food industry as any chemical substance lacking nutritional value, employed to improve organoleptic properties, appearance and product lifecycle. Colourants (sunset yellow: SY and tartrazine: TAR), sweeteners (phenylalanine: PHE, saccharine: SAC, acesulfame-K: ACE and aspartame: ASP) and preservatives (benzoate: BEN) are examples of FAs. However, the adverse effects over human health and the environment arising from its excessive use have overshadowed their boundaries. The present work describes the development of a new, simple, environmentally friendly and multianalyte approach based on capillary electrochromatography-coupled to sample stacking (CEC-SS). CEC-SS was performed employing electrolyte solution of 5 mm Na2B4O7 (pH = 10, β-cyclodextrin (β-CD; 0.25 mm)), hydrodynamic sample injection (0.5 psi, 5 s) and 12 kV of applied voltage. The critical pre-concentration factors of the system were systematically optimised by a Central Composite Design (CCD); under the optimal conditions: injection time of 3.7 min, a pre-concentration time of 3.7 min and a voltage of reverse polarity of 5.3 kV. Pre-concentration factors ranged from 3.6 to 88.0 folds, with limits of detection between 10 and 282 (µg L− 1), inter- and intra-day repeatability with relative standard deviation; %RSD <10% were obtained. Twelve real water samples (tap, bottled and spring water) were used to test the proposed method (CEC-SS). One sample tested positive for BEN (28.0 µg L−1), and two samples tested positive for TAR (spring 129.0 µg L−1). The presented methodology has significant potential for sensitively determining the residues of food additives on complex matrices.