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

Abstract

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 microm. 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 3sigma criterion (without baseline filtering) were 0.6, 0.4, 0.3, 0.5, 0.6, and 0.8 micromol/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.

Investigating the formation and the properties of monoalkyl carbonates in aqueous medium using capillary electrophoresis with capacitively coupled contactless conductivity detection

“…It was equipped with two C 4 Ds [23,24] positioned along the capillary at 10 cm from each end. The experiments were performed using fused silica capillaries (J&W Scientific, Folson, USA).…”

Batch‐injection versus Flow‐injection Analysis Using Screen‐printed Electrodes: Determination of Ciprofloxacin in Pharmaceutical Formulations

“…Forc omparison, capillary electrophoresis (CE) was employed using ah omemade CE equipment [43] with two compact and high resolution capacitively coupled contactless conductivity detectors (CE-C4D)a sd escribed in the literature [35].T he fused-silica capillary was 40 cm long (effective lengthso f1 0a nd 30 cm) and 50 mmi .d. 375 mmo .d.…”

Automated two‐dimensional separation flow system with electrochemical preconcentration, stripping, capillary electrophoresis and contactless conductivity detection for trace metal ion analysis

“…The complete CE instrument, including the C 4 D [21][22][23], was built in the laboratory by do Lago and co-workers and an Electrophoresis 2011, 32, 939-946 improved version of the previously described one [24] was used in this work. The software was developed in LabVIEW 8.0 (National Instruments, TX, USA) in order to integrate the control and data acquisition of the CE-C 4 D equipment with the entire system.…”