Contactless conductivity detector

J. Muzikar, T. van de Goor, B. Gas and E. Kenndler, Extension of the application range of UV-absorbing organic solvents in capillary electrophoresis by the use of a contactless conductivity detector. J. Chromatogr.A 924 (2001) 147-154. 

Kuban, P., and Hauser, P. C. (2005). Application of an external contactless conductivity detector for the analysis of beverages by microchip capillary electrophoresis. Electrophoresis 26, 3169—3178. 

A dual electrochemical microchip detection system, based on the coupling of conductivity and amperometric detection schemes, was developed for simultaneous measurements of both nitroaromatic and ionic explosives [34], The microsystem relied on the combination of a contactless conductivity detector with an end-column thick-film carbon amperometric detector. Such ability to monitor both redox-active nitroaromatic and ionic explosives is demonstrated in Figure 13.7, which shows typical dual-detection electropherograms for a sample mixture containing the nitroaromatic explosives trinitrobenzene (TNB) (4), TNT (5), 2,4-DNB (6), and 2-Am-4,6-DNB (7), as well as the explosive-related ammonium... 

Figure 13.6 Schematic diagram of the dual-end injection CE microchip system with the movable conductivity detector for simultaneous measurements of explosive-related anions and cations, (a) injection mode and (b) separation mode. (a,e) Running buffer reservoirs, (b,d) unused reservoirs, (c, f) sample reservoirs, (g) injected cation plug, (h) injected anion plug, (i) movable contactless conductivity detector, (j—1) cations 1-3, (m-o) anions 1-3. (Reprinted in part with permission from [33]. Copyright 2003 Wiley Interscience.)...

Wang, J., G. Chen, and A. Muck, Jr. Movable contactless conductivity detector for microchip capillary electrophoresis. Anal. Chem. 75, 4475-4479 (2003). 

Bioluminescence detector Charge-coupled device Contactless-conductivity detector Capillary electrophoresis Capillary electrophoresis-Electrochemistry Collision-induced dissociation Chemiluminescence detector Sodium chlorate-nitrobenzene Commercial off-the-shelf (U.S. Army) Cold Regions Research and Development Center Croatian Mine Action Center Council of Scientific and Industrial Research,... 

Other electrode configurations, such as the radial arrangement consisting of four thin wires placed perpendicularly around the circumference of the separation capillary column, have found less application due to more complicated construction and restriction in space and diameter of the separation capillary [56]. Due to its low cost, robustness, minimal maintenance demands, possibility to be freely moved along the capillary [57], or combined with either UV-absorbance [58] or fluorescence [59] detection, the capacitively coupled contactless conductivity detector has recently gained wide acceptance not only for the determination of inorganic ions but also for biomolecules and organic ions, as it has been recently comprehensively reviewed by Kuban and Hauser [1]. 

The measurement electrodes can be wrapped around, threaded onto, or painted over a standard capillary. The use of a grounded shield in between the measurement electrodes greatly reduces stray capacitance. (B) Simplified circuit diagram for a contactless conductivity detector. includes double layer capacitance Cjj as well as the capacitance across the capillary wall. 

P. Kuban and P.C. Hauser, Effects of the cell geometry and operating parameters on the performance of an external contactless conductivity detector for microchip electrophoresis, Lab Chip, 5 (2005) 407-415. J.G.A. Brito-Neto, J.A.F. da Silva, L. Blanes and C.L. do Lago, Understanding capacitively coupled contactless conductivity detection in capillary and microchip electrophoresis. Part 2. Peak shape, stray capacitance, noise, and actual electronics, Electroanalysis, 17 (2005) 1207-1214. 

A contactless conductivity detector was also constructed using 10-p.m A1 foil strips fixed on a 125-p.m-thick PMMA chip with epoxy. Here, the PMMA plate was the dielectric layer. The electrodes were arranged in an antiparallel fashion to minimize stray capacitance between them [772]. 

Electrodes in a capacitively coupled conductivity detector were made by injection molding carbon-filled polymer into a preformed PS chip. The polymer consisted of three conducting formulations 8% carbon black filled PS, 40% C fiber filled nylon-6,6, and 40% C fiber filled high-impact PS [774]. In another report, a movable contactless conductivity detector was also developed to allow the distance of the electrode to be adjustable [775],... 

Human IgM was determined using a homogeneous immunoassay by mouse anti-human IgG on a PMMA chip. CE separation of IgM, IgG, and their complex was achieved and they were detected using a contactless conductivity detector (see Figure 10.3). A LOD value of 34 ng/mL IgM was obtained on the chip, which was different from as 0.15 ng/mL obtained in a capillary tube [1010]. 

Lichtenberg, J., Verpoorte, E., De Rooij, N.F., Operating parameters for an inplane, contactless conductivity detector for microchip-based separation methods. Micro Total Analysis Systems, Proceedings 5th i7AS Symposium, Monterey, CA, Oct. 21-25, 2001, 323-324. 

Wang, J., Pumera, M., Collins, G.E., Mulchandani, A., Measurements of chemical warfare agent degradation products using an electrophoresis microchip with contactless conductivity detector Anal. Chem. 2002, 74(23), 6121-6125. 

Conductivity detection performed with a contactless conductivity detector through the packed bed was shown to be a more versatile and sensitive method than indirect UV detection [77]. Chen et al. employed inductively couple plasma mass spectrometry (ICP MS) as a detection tool for the simultaneous analysis of various ionic species of arsenic, chromium, and selenium [79]. The separation was achieved on an OT CEC column prepared by bonding a macrocyclic polyamine medium on the walls of the capillary. 

Zemann and coworkers have proposed a novel contactless conductivity detector ([Pg.65]

Conventional capillary electrophoresis is useful for separating small inorganic ions in a complex mixture. CE with a contactless conductivity detector has been utilized to separate solutions of cations or anions in under 20 s. Together, inorganic ions and cations were detected in under 2 min. The conductivity detector allows detection of ions that are not UV active. Small anions and cations have also been separated from the complex solutions blood serum and milk. ... 

Fig. 7 Schematic diagrams of the microchip electrophoretic system with the movable contactless-conductivity detector (A) along with a detailed design of the movable electrode system top (B) and bottom (C) views as well as cross-sectional views without (D) and with (E) the PMMA separation chip, (a) Run buffer reservoir, (h) sample reservoir, (c) unused reservoir, (d) movable electrodes, (e) separation chaimel, (f) sample waste reservoir, (g) PMMA chip, (h) conductive silver epoxy, (0 PVC clamps, (/ ) copper wires, (k) aluminum foil electrodes, and (/) Plexiglas plate (Reprinted with permission from Ref. [9])...

Kubnm P, Hauser PC (2005) Effects of the cell geran-etry and operating parameters on the ptaformance of an external contactless conductivity detector for microchip electrophoresis. Lab Chip 5(4) 407-415... 

In the first chapter we recount some of the historical milestones and briefly cover the most basic principles of ion chromatography, or IC as it is often called. The various components and hardware of IC instruments are described in Chapter 2, but it is not our intention to discuss specific commercial instruments. Chapter 3 has been updated to include advances in column technology and promising new columns, such as monolithic columns. Chapter 4 on detectors has been expanded to include new material on the contactless conductivity detector (CCD) and pulsed electrochemical detectors. 

Zemann and coworkers have developed a novel contactless conductivity detector [6-12]. Contactless conductivity detection offers the advantage of avoiding detection dead volumes. This is especially important for miniaturized chromatographic and electrophoresis systems. 

PI A.). Zemann, K. Mayrhofer, E. Schnell. and G. K. Bonn. Contactless conductivity detector for capillary electrophoresis. Book of Abstracts. 216 ACS National Meeting, Boston. August 23-27, ANYLO-75,1998. 

Capacitive coupling contactless conductivity detectors (C4D) which avoid contact with the solutions using high frequencies (>1 MHz) have gained popularity due to their applications in capillary electrophoresis and ionic chromatography [20,21,29,30]. These have also been coupled to flow... 

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