Abstract: A new method was developed for the separation and determination of N-methyldiethanolamine (MDEA) in the desulfurized liquid from refinery by ion-exchange chromatography with non-suppressed conductivity detection using nitric acid as mobile phase. The pretreated sample was passed through a weak acidic cation-exchange analytical column leaching with 7 mmol/L nitric acid at a speed of 1.0 mL/min, rapid separation was achieved and the peaks were well distinguished without significant interference from the others. The detection limit of MDEA was found to be as low as 0.638 3 mg/L. The relative standard deviations were 1.03 % (n = 8, measuring peak area) and 0.94 % (n=8, measuring retention time). Linear calibration curve in the range corresponding to 5.00-500 mg/L was obtained for MDEA. Determinations of rich liquor and barren liquor containing MDEA from refining process were carried out and the recovery (n=3) of MDEA was found to be in the range of 99.1 % ~100.3 % with relative standard deviations less than 3%.

Key words: ion-exchange chromatography, non-suppressed conductivity detection, N-methyldiethanolamine (MDEA), weak acidic cation-exchange column