Borate complexation-assisted capillary electrophoretic determination of ethylene glycol and propylene glycol using capacitively coupled contactless conductivity detection

• Borate ester formation allows CE separation of ethylene glycol (EG) and propylene glycol (PG) • C 4 D is suitable for the direct detection of EG and PG using CE • CE-C 4 D enables simple, rapid, and derivatization-free determination of EG and PG A novel, fast, and reliable analytical method for determining ethylene glycol (EG) and propylene glycol (PG) using capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C 4 D) is proposed. The CE separation is based on the anionic complexation of the glycols with borate ions in the background electrolyte (BGE). The borate concentration in the BGE was optimized, and 100 mmol L -1 provided the best compromise between adequate resolution and acceptable Joule heating. Separation of both glycols was achieved in less than 5 min, with suitable baseline resolution. Good linearity was attained with coefficients of determination higher than 0.99. The limits of detection (LOD) and quantification (LOQ) were 18.8 and 62.7 µg mL -1 for EG and 21.1 and 70.4 µg mL -1 for PG, respectively. The recovery results for the samples analyzed at three concentration levels ranged from 86% to 113%, indicating good accuracy. The proposed CE-C 4 D method was successfully applied to determine EG and PG in various samples, including engine coolant, mouthwash, and e-liquid (refill for electronic cigarettes).