Renaissance of HF Impedimetry in Application to CE Detection

Abstract

Some results obtained at the above department in the field of contactless conductivity detection (CCD) are reviewed, in the framework of the state-of-the-art of the field. Several detection cells have been designed and tested. It has been shown that the performance of systems with planar and semitubular electrodes is fully comparable with that of common cells with tubular electrodes and that these systems have advantages in simpler construction and a greater operational versatility. Important characteristic parameters are discussed, primarily the electrode effective length, the gap between the electrodes and the thickness of the dielectric layer. Possibilities of using thin insulated wire electrodes for CCD detection in flow injection analysis are demonstrated.

A thin-layer contactless conductivity cell for detection in flowing liquids

“…This is in agreement with the previous observations on the functioning of contactless conductivity cells [28][29][30] from which it follows that the electric current passes through an effective electrode width which is different from the geometric electrode width. The dependence of the cell impedance on the electrode width passes through a minimum and the current flowing through the cell follows this minimum.…”

“…[28,30] that the electrode effective width is a complex function of the test solution conductivity, the signal frequency and the width of the gap between the electrodes. When using the above model, it can also be demonstrated that the electrode effective width also depends on the thickness of the insulator layer between the electrodes and the solution: the effective width increases with increasing insulator thickness.…”

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

“…Even a photothermal process has been employed for detection, combined with CCD [95]. Two recent papers deal with the CCD theory [86,96], one paper compares various CCD detectors for determination of small inorganic ions [97] and a few papers review the field [17,18,20,98].…”

“…Data given in Table 1 are estimated values obtained without preconcentration methods [14,40,58,94,98].…”

Application of Contactless Impedance Detection to Determination of Substances in Gaseous Phase

“…Under these conditions, the experimental dependences are better defined, their non-linearity is considerably suppressed and the measurements have become sensitive and reliable. Consequently, there has been rapid progress in the cell design and in extensive application of high-frequency impedimetry, primarily to monitoring of various substances in liquids and to detection of analytes in microfluidic systems, in capillary electrophoresis, flowinjection analysis and liquid chromatography [10][11][12][13]. The most common approach to all these measurements is the monitoring of the resistance component of the impedance, which depends on the test solution conductivity.…”