Abstract:

Micellar electrokinetic capillary chromatography (MECC) with indirect ultraviolet (UV) detection method for the separation and determination of several organic acids in cane vinasse, including malonic, formic, tartaric, malic, succinic, glutaric, acetic, lactic and glutamic acids, were developed. Electrophoretic conditions were as follows: uncoated fused silica capillary (56 cm/64 cm(effective/total length), 50 μm i.d.), 7.5 mmol/L potassium acid phthalate-1.5 mmol/L cetyltrimethyl-ammonium bromide (CTAB) at pH=6.50 as buffer solution, applied voltage -25 kV, temperature 25 ℃, detection wavelength 300 nm, reference wavelength 210 nm. Good linearities were obtained for nine organic acids, and the detection limits were 0.5 mg/L, 0.3 mg/L, 1.5 mg/L, 1.5 mg/L, 0.3 mg/L, 0.3 mg/L, 0.4 mg/L, 0.4 mg/L, 0.4 mg/L for malonic, formic, tartaric, malic, succinic, glutaric, acetic, lactic and glutamic acid, respectively. The relative standard deviations (RSDs) for migration times and peak areas of nine organic acids within a day were 0.4%-0.6% and 2.3%-4.8%, respectively. The corresponding data for five days were 0.5%-0.7% and 3.3%-5.2%. The recoveries of acid standards were above 93%. The method can be applied to determine the organic acids in cane vinasse with satisfactory results.

Key words: cane vinasse , indirect UV detection；organic acid, micellar electrokinetic capillary chromatography (MECC)