几种无机阳离子的毛细管电泳电容耦合非接触电导分离检测

Determination of Some Inorganic Cations by Capillary Electrophoresis with Capa citively Coupled Contactless Conductivity Detection

研制出电容耦合非接触电导检测器,检测器使用两个5mm长的管状电极套在分离毛细管的外面,电极相距2mm并与函数信号发生器连接。对影响检测器检测限和线性范围的激发频率、峰峰电压(Vp p)等因素进行了考察,结果发现频率为25～35kHz、Vp p在30V时检测器有最佳的信号噪声比;以2 N 吗啡啉乙磺酸(MES) 组氨酸(His)为缓冲体系,用自制的检测器对Li+,Na+,K+,Mg2+,Ca2+和Ba2+等几种常见的无机离子进行了毛细管电泳分离检测,优化了缓冲溶液的pH值、浓度和分离电压等条件,当缓冲液中MES与His的浓度均为10mmol/L、pH值为5 0和分离电压为10kV时,体系有最好的分离效果;在最佳的分离检测条件下,6种离子的检测限依次为:16,13,5,10,10和8μmol/L,响应线性范围为10-6～10-3mol/L,相关系数大于0 999。

A capacitively coupled contactless conductivity detector (C4D) for capillary e le ctrophoresis was designed and evaluated. The detector consisted of two 5 mm met al electrodes, which were placed cylindrically around the polyimide coating o f a fused-silica capillary (50 μm id and 375 μm od) and separated by a 2 mm detection gap. A function generator was used to apply a sinusoidal signal over the electrodes. The effects of excitation frequency and peak-to-peak vol tage (Vp-p) on the detection limits and linear dynamic range of respo nses were investigated. The detector showed the highest signal-to-noise ratio in the range of 25-35 kHz and the voltage 30 V. Separation of six inorganic cati ons (Li+, Na+, K+, Mg2+, Ca2+ and Ba2+) was achieved in the capillary electrophoresis system with the C4D. The separation parameters, such as pH, concentration of the electrolyte, separation volta ge were studied. Best separation were achieved with electrolytes consisting of 1 0 mmol/L 2-(N-morpholino) ethanesulfonic acid (MES), 10 mmol/L L-histidine (L-His) at pH 50, and 10 kV separation voltag e. Under the optimized conditions, the detection limits for the six cations were 16, 13, 5, 10, 10, and 8 μmol/L, respectively, with linear dynamic ranges from 10-6 to 10-3 mol/L(correlation coefficients (r) more th an 0999).