Detectors pulsed electrochemical

HPAEC analyses were carried out to determine the oligomeric products released from various pectic substrates after depolymerization by the PL isoenzymes. Action pattern analyses for the concerted action of PL isoenzymes utilized 68% esterified pectin as substrate. One-ml reaction mixtures in a buffer system as detailed in section 2.2. comprising 0.5% (w/v) substrate and 5 U of enzyme were incubated for 30 s to 18 h, and then thermoinactivated. Samples of 750 pi were applied to a Carbopac PA-1 (Dionex) column before the carbohydrates were eluted over a period of 70 min using a gradient of 0.2 M KOH, 0.05 M K-acetate to 0.2 M KOH, 0.7 M K-acetate. Detection employed a Pulsed Electrochemical Detector (PED, Dionex) in the integrated amperometry mode according to the manufacturer s recommendations. 

Pulsatile drug delivery systems, 9 57-61 Pulsating heat pipes (PHP), 13 235-236 Pulse combustion heat sources, 9 104-105 Pulse cycles, 9 778 Pulsed baffle reactors, 15 709-710 Pulsed discharge detector (PDD) gas chromatography, 4 614 Pulsed dye lasers, 23 144 Pulsed electrochemical machining (PECM), 9 604-605... 

Biometra GmbH (1992) Instructions for pulsed electrochemical detector PAD 300... 

Adamic and Bartak [6] used high pressure aqueous size exclusion chromatography with reverse pulse amperometric detection to separate copper(II) complexes of poly(amino carboxylic acids), catechol and fulvic acids. The commercially available size exclusion chromatography columns were tested. Columns were eluted with copper(II) complexes of poly(aminocarboxylic acids), citric acids, catechol and water derived fulvic acid. The eluent contained copper(II) to prevent dissociation of the labile metal complexes. Reverse pulse electrochemical measurements were made to minimise oxygen interferences at the detector. Resolution of a mixture of DTP A, EDTA and NTA copper complexes was approximately the same on one size exclusion chromatography column as on Sephadex... 

Chloride ion concentration was measured by ion chromatography with a Dionex Bio LC chromatograph equipped with a Dionex pulsed electrochemical detector and a Dionex PAX-100 metal-free anion column (25 cm long, 4.6 mm i.d.). The eluent was a mixture of 80% H20, 10% acetonitrile, and 10% 191-mM NaOH the flow rate was 1 mL/min, and the injection loop volume was 50 p,L. 

Detector E, Dionex pulsed electrochemical detector, integrated timperometry mode, 1.4 mm gold working electrode with 0.005 inch gasket, El -t0.07 V, tl 400 ms, E2 -1-0.70 V, t2 120 ms, E3 1.00 V, t3 300 ms, stainless steel counter electrode, Ag/AgCl reference... 

Detector E, Waters Model 464 pulsed electrochemical detector, + 1 V versus Ag/AgCl... 

BAKER CAPILLARY ELECTROPHORESIS CUNNINGHAM INTRODUCTION TO BIOSENSORS LACOURSE PULSED ELECTROCHEMICAL DETECTORS IN HPLC... 

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. 

With some help from William La Course (see Acknowledgements), Chapter 4 on Detectors has been expanded and completely rewritten. New features include a strong section on pulsed electrochemical detection and an extensive table of dyes for tagging for the fluorescent detection of bio ions. 

Ion chromatography is used to perform separation and detection of inorganic anions and cations, organic acids, and electroactive organic compounds. This instrument may be configured with a variety of detectors such as conductivity, pulsed electrochemical, and UV-visible detectors. Applications include the determination of anions in electronic-grade materials, residual organic acid in polymers and copolymers, and blend formulations. 

Tfue self-test and self-diagnosis remain rare. Instead, the approach commonly taken is to maintain the activity of the system by periodic regeneration procedures as long as possible. On the other hand, disposable sensors are a useful alternative. For amperometric sensors and detectors, complex electrochemical pulse sequences which renew the electrode surface are applied widely. 

Specifications for modem detectors in HPLC are given by Hanai [538] and comprise spectroscopic detectors (UV, F, FUR, Raman, RID, ICP, AAS, AES), electrochemical detectors (polarography, coulometry, (pulsed) amperometry, conductivity), mass spectromet-ric and other devices (FID, ECD, ELSD, ESR, NMR). None of these detectors meets all the requirement criteria of Table 4.40. The four most commonly used HPLC detectors are UV (80%), electrochemical, fluorescence and refractive index detectors. As these detectors are several orders of magnitude less sensitive than their GC counterparts, sensor contamination is not so severe, and... 

Electrochemical detectors are more sensitive to flow pulsation than UV-detectors and usually an efficient pulse dampener is required to minimize the contribution to baseline noise at high sensitivity. 

Electrochemical detectors, which are based on the electrochemical oxidation or reduction of the analyte, can be applied to the analysis of selected compounds such as phenols. It is physically simple, but is very sensitive for catecholamines. However, the adsorption of reacted molecules on the surface of the electrodes can reduce the conductivity. To overcome this problem a pulsed voltage is applied, which cleans the electrode surface between measurements. This pulsed amperometric detection is also sensitive for carbohydrates. 

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