Direct simultaneous determination of eight sweeteners in foods by capillary isotachophoresis

A method for isotachophoretic determination of sweeteners of different character in candies and chewing gums was developed. A capillary of 0.8 mm ID and 90 min effective length made of fluorinated ethylene-propylene copolymer is filled with an electrolyte system consisting of 10 mM HCl + 14 mM Tris, pH 7.7 (leading electrolyte) and 5 mM L-histidine + 5 mM Tris, pH 8.3 (terminating electrolyte). The analysis is performed at a driving current of 200 mu A and for detection current is decreased to 100 mu A. Boric acid is added to the aqueous sample solution to form borate complexes with substances of polyhydroxyl nature and make them migrate isotachophoretically. Using conductivity detection, the calibration curves in the tested concentration range up to 2.5 mM were linear for all components of interest: acesulfame K, saccharine, aspartame, cyclamate, sorbitol, mannitol, lactitol, and xylitol. The concentration detection limits ranged between 0.024 and 0.081 mM. Good precision of the ITP method is evidenced by favorable RSD values ranging from 0.8 to 2.8% obtained at the analyte concentration of 1.0 mM (n = 6). The analysis time was about 20 min. Simplicity, accuracy, and low cost of analyses make ITP an alternative procedure to methods used so far for the determination of ionizable sweeteners.