Miniaturized movable contactless conductivity detection cell for capillary electrophoresis

Abstract

A miniaturized capacitively coupled contactless conductivity detector (mini-C(4)D) cell has been designed which is small enough to allow it to slide along the effective capillary length inside the capillary cassette of an Agilent capiillary electrophoresis system (CE) (or other CE brand of similar construction), including the possibility of positioning it close to the point of optical detection (4 cm), or even putting two such detector cells in one cassette. The cell was tested and the performance characteristics (noise, sensitivity, and peak width) were compared with those obtained with the previously used large C(4)D cell. No significant differences were observed. The mini-C(4)D was used in simultaneous separations of common cations and anions where its advantage over a larger C(4)D cell is the ability to vary the point of detection with the mini-C(4)D cell continuously at any point along the capillary length, so that the optimum apparent selectivity can be chosen. Other applications include providing a convenient second point of detection in addition to photometric detection, such as to measure accurately the linear velocity of a zone, or to allow placement of two mini-C(4)D cells in one capillary cassette simultaneously.

Contactless Conductivity Detection in Capillary Electrophoresis: A Review

“…The simultaneous separation of anions and cations with dual opposite-end injection was also demonstrated in PEEK capillaries [41]. A detailed study on the effect of the position of the detector along the capillary was carried out by Macka et al [39]. By using plots of apparent selectivities, the best placement of the CCD cell was easily found.…”

“…Fracassi da Silva et al [25] presented a miniaturized detector incorporated on a printed circuit board with dimensions of only 18 Â 18 mm. Hilder et al [37], Vuorinen et al [38] and Macka et al [39] designed miniaturized versions of the CCD cell for easy incorporation into existing commercial instruments. Kappes et al [40] incorporated a CCD into a purpose built portable CE instrument.…”

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

“…Injection of inorganic ions was performed hydrodynamically at 50 mbar for 7 s, which represents less than 1% of the total capillary volume. The detector with a miniaturized cell was constructed at the University of Tasmania and was described elsewhere [17]. The high-voltage detector was constructed at the University of Basel and is based on electronics referenced in [19,20].…”

“…Generally the systems consist of two parts, a detector cell and a separate case containing the associated electronics. Macka et al [17] and Vuorinen et al [18] described very small detector cells for easy placement into existing commercial CE instruments which were not originally designed for retrofitting of alternative detectors. Tanyanyiwa et al [19,20] described a system which was constructed for high signal to noise ratio by using an elevated excitation voltage and a detector cell which includes a pre-amplifier.…”

Portable capillary-based (non-chip) capillary electrophoresis

“…Its main weakness is the need to have a significant difference between the conductivity (mobility) of the de-tected ion and the background electrolyte (co-ion mobility). However, most inorganic [119] as well as organic [120] cations and anions can be determined with typical LODs at the level of M. In terms of miniaturization, one of the smallest capil-lary C 4 D cells allowing integration into the commercial Agilent cassette was the detector constructed by Macka et al [121]. In this small design, the miniature electrodes and supporting plastic elements on a piece of CE capillary were encased in epoxy resin (as shown in Fig.…”