New Developments in Capillary Ion Chromatography Systems with Electrochemical Detection and Their Applications (original) (raw)
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Recent developments in electrolytic devices for ion chromatography
Journal of Biochemical and Biophysical Methods, 2004
Recent developments in new electrolytic devices that utilize the electrolysis of water and chargeselective electromigration of ions through ion-exchange media have significantly changed the routine operation of ion chromatographic methods. Examples of these new electrolytic devices include online eluent generators that produce high-purity electrolyte eluents using deionized water as the carrier stream, continuously regenerated trap columns that remove ionic contaminants in the eluents, and continuously regenerated suppressors that reduce eluent background conductance prior to conductivity detection. The combined use of these electrolytic devices has made it possible to perform various ion chromatographic separations using only deionized water as the mobile phase. This paper reviews the operation principles of these electrolytic devices and their applications in the ion chromatographic determination of anionic and cationic analytes. D
On-Line Gas-Free Electrodialytic Eluent Generator for Capillary Ion Chromatography
Analytical Chemistry, 2008
Both low-and high-pressure, gas-free, capillary-scale electrodialytic generators for eluents in ion chromatography are described. While the low-pressure devices rely on planar or tubular membranes, the high-pressure devices rely on ion-exchange beads used both as one-way ionic gates and as ball-on-seat valves to provide sealing. The high-pressure device is easily implemented in the form of a commercial cross fitting and can withstand at least 1400 psi. By design these devices do not produce gas in the eluent channel; hence, it is not necessary to remove gas afterward. With appropriate electrolytes and electrode polarities, such devices can produce either acid or base or salt. In regard to ionic transport, the behavior of these devices fully corresponds to that of a semiconductor diode. To our knowledge, this is the first time such complete equivalence of ion transport through ionexchange media and with the more familiar example of electron transport through a semiconductor diode under both forward-and reverse-biased conditions have been demonstrated. Reverse bias can be applied to minimize/ prevent Donnan-forbidden leakage or ion exchange. Even with 4 M KOH in the electrode compartments and 4 µL/ min water flowing through the eluent channel, with a reverse bias of-12 V, the leakage KOH concentration is <30 µM, whereas the KOH concentration with zero voltage applied, hereinafter termed open circuit penetration (OCP), is 1600 µM. It is suggested that this OCP occurs not as much through Donnan-forbidden leakage but via ion exchange. Chromatograms and reproducibility data are presented for both isocratic and gradient chromatography, using ion-exchange, latex-modified, open tubular and packed monolithic columns.
Journal of Chromatography A, 2001
Capillary electrophoresis (CE) with mass spectrometry (MS) detection is an ideal tool for analytical use, which combines a nano quantity assay with mass determination. Carbohydrate analysis has always been a challenge because of the inherent structural complexity and the lack of a chromophore, unless derivatization is used. Here we use the derivatization of carbohydrates with a fluorophore, 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS). This chromophore has two advantages, first, it facilitates UV and fluorescence detection and, second, it introduces negative charge to the analyte, which enhances zone electrophoretic separation. In this study, CE combined with negative ion electrospray MS (ESI-MS) was evaluated for the on-line analysis of ANTS labeled carbohydrates and cellulose fragments. The CE system was connected to the MS by a sheath-liquid electrospray arrangement. The ANTS reagent and Dextrin-15, which contains oligomers of maltose, were used as model samples for ESI-MS optimization in flow-injection-MS and CE-MS modes, respectively. Various sheath-liquid compositions regarding organic modifier (isopropanol, methanol, or acetonitrile) and electrolyte (acetic acid-formic acid, ammonium acetate, or triethylamine) were studied. The response as well as the analyte charge state distribution was found to be dependent on the composition and the orifice voltage. Low-pH conditions with isopropanol as organic modifier were sensitive, stable, and the most favorable for analysis.
ELECTROPHORESIS, 2011
A method for adapting widely used CE conditions for the separation of fluorescently labeled carbohydrates to permit online ESI-MS detection is presented. Reverse polarity separations were performed in bare fused-silica capillaries with an acidic BGE. Under these conditions, negatively charged 8-aminopyrene 1,3,6-trisulfonate-labeled carbohydrates migrate forward against the EOF, which is towards the capillary inlet. Therefore, the CE-MS interface must simultaneously back-fill the capillary, in order to maintain the CE circuit, and provide a stable forward flow at the sprayer tip to support the electrospray process. This was achieved using a junction-at-the-tip interface, which provides a flow of solution to the junction formed by the capillary terminus and the inner wall of the emitter needle tip. Because the flow rate required for this arrangement is much less than in conventional sheath flow interfaces, dilution of the analytes is minimized. Optimized separation conditions permit baseline resolution of glucose oligomers containing up to 15 glucose units, while longer oligomers, up to 33 glucose units, were observed as resolved peaks in the negative ion mode mass spectrum.
Capillary Electrochromatography A Versatile Tool for Biochemical Analysis
Capillary Electro chromatography (CEC) is a small scale separation technique which involves principle of both chromatography and capillary electrophoresis. Separation of analyte is done on the basis of differences in ratio of partition between stationary phase and mobile phase or due to differences in their electrophoretic mobility. Capillary Electro chromatography (CEC) combines the principles used in HPLC and CE. The mobile phases are driven across the chromatographic bed using electro osmosis instead of pressure (as in HPLC). This review describes the general introduction to CEC, the various advantages of CEC over HPLC and Electophoresis, instrumentation, history, various stationary phase and mobile phases, column technology and vast applications of CEC in a variety of fields.
ELECTROPHORESIS, 2004
Large-scale carbohydrate analysis by capillary array electrophoresis: Part 1. Separation and scale-up A 96-capillary array electrophoresis (CAE) instrument has been adapted for large-scale mono-and oligosaccharide analysis and characterization. Operational protocols and data processing tools have been developed to optimize the CAE system for this application. Effects of different additives to the running buffer on efficiency and capillary-to-capillary performance reproducibility have been studied.
Journal of High Resolution Chromatography, 1996
Carbohydrates were separated by capillary electrophoresis (CE) and detected electrochemically using a nickel microelectrode which was operated at a constant applied potential (-0.6 V YS. Ag/AgCI). A simple capillary electrode holder design facilitated alignment between the separation capillary and the working microelectrode without the use of micro-positioning equipment. The separations were performed under alkaline conditions (pH > ll), matching the high pH requirements for amperometric detection at the nickel electrode. The analytical procedure developed showed detection limits for the carbohydrates studied in the micromolar range, showing a linear response in the range tested (micromolar to millimolar). The procedure was used to identify sugars in two real samples (k., urine and in a common beverage). The potential use of the system for the determination of amino acids was also demonstrated.
Analytical Chemistry, 1993
Caplllary zone electrophoresis (CZE) was employed to separate sugars accordlng to their electrophoretic moMlitks In strong alkallne clolutlons (pH ca. 13). Saccharide zones were monltored electrochemlcaliy udng amperometrlc detectlon at a constant potentlal, 0.6 V (vs Ag/AgCI), with a cyllndrlcal copper wire electrode (25 pm In diameter). The Cu-wire microelectrode In strong badc solutions had electrochemlcal behavlor slmllar to that of Cu electrodes with larger dlmendono and appeared to &ow no deterloratton for hundreds of runs. A sample mixture contalnlng 15 different sugars was separated In l e r than 45 mln with reparation efflclencles up to 200 000 theoretical plates. The callbratlon plot was found to be llnear over 3 orders of magnitude and the llmits of detection for the saccharides studied were In the femtomole range.
2004
Large-scale carbohydrate analysis by capillary array electrophoresis: Part 1. Separation and scale-up A 96-capillary array electrophoresis (CAE) instrument has been adapted for large-scale mono-and oligosaccharide analysis and characterization. Operational protocols and data processing tools have been developed to optimize the CAE system for this application. Effects of different additives to the running buffer on efficiency and capillary-to-capillary performance reproducibility have been studied.
A multifunctional dual membrane electrodialytic eluent generator for capillary ion chromatography
Journal of Chromatography A, 2009
A multifunctional electrodialytic generator (EDG) for capillary ion chromatography (CIC) is described. The same device can generate acidic, basic or saline eluents. Two oppositely charged ion exchange beads are used to fabricate the EDG; the dual ion exchanger configuration ensures the production of gas-free eluent, obviating the need of a gas removal device used with single ion exchanger EDG's. The ability of the same EDG to produce different eluents is governed solely by the choice of the respective feed solutions; this is presently demonstrated by generation of diverse eluents such as Na 2 CO 3 /NaHCO 3 , CH 3 SO 3 H, and KNO 3. The EDG is implemented simply in a commercial cross fitting and has been tested up pressures to 2000 psi. Under typical operating conditions, the zero current concentration (open circuit penetration, OCP) is negligible. The generated eluent concentration linearly increases with applied current with a slope that is essentially Faradaic. The device permits both isocratic and gradient operation with good reproducibility, as demonstrated by the analysis of anions using HCO 3 − /CO 3 2− EDG.