Comparison of Different Contactless Conductivity Detectors for the Determination of Small Inorganic Ions by Capillary Electrophoresis

Abstract

The analytical performance parameters of four different contactless conductivity detectors for capillary electrophoresis were determined. These detectors were designed either with a miniature cell for versatility, with high voltage excitation for high sensitivity or with a battery power supply for field application. One of the units is commercially available. The plate numbers and reproducibility of peak areas (typically about 2%) were very similar, indicating that these parameters are generally limited by the separation and injection procedures rather than the detectors. The linear dynamic ranges are better than 2 orders of magnitude for all detectors and the correlation coefficients were also almost identical. Significant differences were found with regard to the detection limits. For the detector with a miniature cell, which lacks an in-cell amplifier, the detection limit was typically 1.5 mM for the inorganic ions tested (K þ , Ca 2þ , Na þ , Mg 2þ , Li þ , Cl À , NO 3 À and SO 4 2À ), while with the other 3 detectors this parameter was as low as about 0.1 mM. The use of buffer solutions with relatively high background conductivity was found to lead to detection limits which were up to one order of magnitude higher. The extent of deterioration of this parameter with buffer conductivity was found to be related to the excitation voltage and was most pronounced for the high voltage detector.

New Fully Portable Instrument for the Versatile Determination of Cations and Anions by Capillary Electrophoresis with Contactless Conductivity Detection

“…This approach was not possible for the field instrument because of its power requirement. A comprehensive comparison between the new battery powered detector and the earlier design, as well as a commercially available unit, has been reported previously [23]. It was found that a performance in terms of precision and detection limit very similar to the other two detectors could be achieved when evaluating these on a commercial CE-instrument.…”

Identification of inorganic ions in post‐blast explosive residues using portable CE instrumentation and capacitively coupled contactless conductivity detection

“…This detector has previously been compared with several other contactless conductivity detectors in our laboratory and has been shown to provide the lowest LOD for inorganic ions [38]. A high-sensitivity detector head was used and this was positioned 8 cm from the outlet end of the capillary.…”

An evaluation of the experimental approaches to detection of small ions in CE

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