Indirect UV Detection of Short Chain Carboxylic Acids in Oil Field Water by High Performance Capillary Zone Electrophoresis
毛细管区带电泳法测定油田水中的脂肪酸

Short chain carboxylic acids are the major aqueous organic species in oil field water. It is considered that they play an important role in the geochemical evolution of second porosity in oil reservoir. In this paper, short chain carboxylic acid anions were analyzed by HP(3D)CE high performance capillary electrophoresis system (Hewlett-Packard, Germany) with a buffer system of dinitrobenzoic acid-hexadecyltrimethyl ammonium bromide (CTAB). The influence of buffer pH and the concentrations of electrolyte, surfactant and methanol on the seperation of short chain carboxylic acids have been studied. The results showed that the best separation of short chain carboxylic acids could be done with the buffer of 10mmol/L dinitrobenzoic acid, 0.5mmol/L CTAB and 5% methanol at pH=9. Separations were performed in a 50cm x 50microm i.d. fused silica capillary (effective length 48.5cm) at 25 degrees C. A negative potential of 30kV was used for each experiment. Sample was introduced into the capillary by pressure at 50kPa for 10s. Indirect UV detection was operated at 254nm and reference wavelength at 380nm for all experiments. Negative peak was changed into positive one by exchanging between detection wavelength and reference wavelength. Capillary was rinsed for 10min with 0.1mol/L sodium hydroxide and buffer solution before each run. Oil field water was injected directly after filtered through 0.45microm membrane. The result was satisfactory.