A compact and high-resolution version of a capacitively coupled contactless conductivity detector

作者：Mendonca Francisco Kelliton Jose; do Lago Claudimir Lucio^*

来源：Electrophoresis, 2009, 30(19): 3458-3464.

DOI：10.1002/elps.200900080

• Alkaline ions
• Caffeine
• Contactless conductivity detection
• Detection
• Dynamic range

An all-in-one version of a capacitively coupled contactless conductivity detector is introduced. The absence of moving parts (potentiometers and connectors) makes it compact (6.5 cm(3)) and robust. A local oscillator, working at 1.1 MHz, was optimized to use capillaries of id from 20 to 100 lam. Low noise circuitry and a high-resolution analog-to-digital converter (ADC) (21 bits effective) grant good sensitivities for capillaries and background electrolytes currently used in capillary electrophoresis. The fixed frequency and amplitude of the signal generator is a drawback that is compensated by the steady calibration curves for conductivity. Another advantage is the possibility of determining the inner diameter of a capillary by reading the ADC when air and subsequently water flow through the capillary. The difference of ADC reading may be converted into the inner diameter by a calibration curve. This feature is granted by the 21-bit ADC, which eliminates the necessity of baseline compensation by hardware. In a typical application, the limits of detection based on the 3 sigma criterion (without baseline filtering) were 0.6, 0.4, 0.3, 0.5, 0.6, and 0.8 mu mol/L for K( ), Ba(2 ), Ca(2 ), Na( ), Mg(2 ), and Li( ), respectively, which is comparable to other high-quality implementations of a capacitively coupled contactless conductivity detector.

• 出版日期2009-10