Ultrasensitive Determination of Artificial Sweeteners in Environmental Water Samples Through Capillary Electrophoresis Coupled With Capacitively Coupled Contactless Conductivity Detection

A dual-enrichment method based on efficient sample cleanup offline ion-pair ultrasonic surfactant-assisted dispersive liquid-liquid microextraction coupled with efficient sample stacking through online field-amplified sample stacking was devised for the concurrent determination of three artificial sweeteners (acesulfame potassium, saccharin, and cyclamate) using capillary electrophoresis (CE) coupled with capacitively coupled contactless conductivity detection. Various parameters that affected the CE separation performance and the enrichment efficiency of ion-pair ultrasonic surfactant assisted dispersive liquid-liquid microextraction and field-amplified sample stacking were optimized, and excellent CE separation was attained within 20 min. The optimal ion-pair ultrasonic surfactant-assisted dispersive liquid-liquid microextraction method used 240 µL of chlorobenzene as the extraction solvent, 125 µM N-methyl-N, N-dioctyloctan-1- ammonium chloride as the surfactant, and a pH of 7. Sample stacking was achieved by field amplified sample stacking in a 65 mM butyric acid buffer (pH 2.95), and the signal was detected by capacitively coupled contactless conductivity detection (2 Vpp, 200 kHz). Under the optimized conditions, the proposed method achieved enrichment factors ranging from 3158 to 3261. The linear concentration range was found to be 0.3-30 nM (r > 0.9993). The limits of detection for the three artificial sweeteners were in the range of 0.092-0.095 nM. Good precision was verified by the low relative standard deviations for migration times (3.0%) and peak areas (9.0%). The method was successfully applied to spiked environmental water samples. The relative errors for accuracy ranged from -3.4% to 7.5% for lake water, -8.8% to -0.3% for river water, and -6.8% to 9.6% for groundwater. Consequently, this method represents an efficient, rapid, and low-cost technique for extracting and determining artificial sweeteners in environmental water matrices.