Determination of Monoethylene Glycol in Gas Condensate Samples by Microchip Micellar Electrokinetic Chromatography Integrated With Capacitively Coupled Contactless Conductivity Detection

This study describes the use of microchip micellar electrokinetic chromatography (MEKC) integrated with capacitively coupled contactless conductivity detection (C⁴D) for the determination of monoethylene glycol (MEG) in gas condensate samples. The samples were subjected to a liquid-liquid extraction step and then analyzed by chip-based MEKC-C⁴D. For this purpose, sodium dodecyl sulfate (SDS) was used as a surfactant at a concentration of 30 mmol L^-1 added in 50 mmol L^-1 phosphate (pH = 9.0). Samples were introduced into microchannels through floating injection mode by applying a voltage of 600 V during 10 s. Separations were performed under an electric field of 82 V cm^-1 and monitored by C⁴D measurements recorded applying a 1200-kHz frequency sinusoidal wave with 20-V_pp excitation voltage. The proposed methodology employing MEKC-C⁴D revealed a linear behavior (r² ≥ 0.99) in the MEG concentration range between 150-450 µmol L^-1 and LOD equal to 33 µmol L^-1. Three gas condensate samples were then analyzed, and the achieved MEG concentration values ranged from 173 to 213 µmol L^-1. Recovery experiments provided values between 89 and 102%. Based on the results reported in this study, MEKC-C⁴D devices have demonstrated to be a promising and ecological analytical tool for MEG analysis with huge potential for in-field applications.