Computer-controlled coulostatic stripping analysis

Schreiber, Mark A.

doi:10.1021/ac00236a034

Cited by 15 publications

(8 citation statements)

References 26 publications

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“…The development of computer-controlled electrochemical instrumentation has prompted a rebirth of interest in coulostatic analysis (18,21,22). In coulostatics, a charge pulse of known coulombic content is injected into a cell on a time scale much more rapid than the time scale for electron transfer between the electrode and electroactive species in solution.…”

Section: Theorymentioning

confidence: 99%

Coulostatic pulse amperometry for liquid chromatography/electrochemistry detection

Barnes¹,

Nieman²

1983

Anal. Chem.

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Small charge pulses are repetitively Injected Into the cell to maintain the the working electrode at the desired potential. Because the method Is not Interfered with by charging current, the potential can be changed rapidly; 10-polnt voltammograms are run In 1-2 s. Caffelc acid and o-chlorophenol are quantitated at fixed potential In a flow Injection system over the range of 1-100 µ with 4% precision. Hydrodynamic voltammograms were run for caffelc acid solutions as dilute as 0.5 µ . For a liquid chromatographic separation of

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Section: Theorymentioning

confidence: 99%

Coulostatic pulse amperometry for liquid chromatography/electrochemistry detection

Barnes¹,

Nieman²

1983

Anal. Chem.

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“…A voltammetric detector which is based on the coulostatic principle is described here. The coulostatic electrochemical technique is almost completely immune from double-layer charging effects (4,5). Therefore, with this detector it is possible to scan the potential at rates up to 3 V/s while still maintaining good detection limits.…”

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confidence: 99%

Coulostatic voltammetric liquid chromatography detector

Last¹

1983

Anal. Chem.

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A coulostatic electrochemical detector was developed for use In flowing streams. The detector Is capable of scanning the applied potential at rates of up to 3 V/s and recording multiple channel chromatograms, where each channel corresponds to a separate electrode potential. The faradaic current Is measured between coulostatic pulse applications, at which time no current flows In the bulk solution passing through the detector. The detector was able to resolve and quantitate liquid chromatographic peaks which were completely overlapped In the time domain, provided that the half-wave potentials of the components differed by more than 0.25 V. The Instrument exhibited good precision and linearity for acetaminophen samples ranging from 6.85 ng to 1 pg In mass. The relative standard deviation for three determinations at the 6.85 ng level was 3.8%.Electrochemical liquid chromatographic detectors have become very popular (1) due to their high sensitivity and the increased selectivity afforded by a judicious choice of the applied potential. However, for an unknown sample, one must select the proper applied potential through a trial-and-error approach, or use another technique, (e.g., cyclic voltammetry) to determine the optimum value. Further, while it is often possible to select a potential at which an unwanted peak is eliminated, it is impossible to resolve overlapping peaks and simultaneously quantitate both components. This problem can be alleviated to some degree through the use of multiple electrode cells (1); however, in general, each set of overlapping peaks would require two separate working electrodes with a different control potential at each. A more suitable solution to this problem is to rapidly scan the potential repeatedly during the elution and concurrently record chromatograms at several different potentials. In this way, the voltage axis can be used to resolve peaks which are overlapped in the time domain, and all resolved peaks can be accurately quantitated.

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“…Among the available methods of enzyme immobilization, four methods are currently used: adsorption followed by reticulation with bifunctional reagents such as glutaraldehyde (1), covalent coupling between enzyme and activated support (2)(3)(4)(5) or activated enzyme and support (6)(7)(8), and reversible immunological coupling (9). Those involving covalent coupling to solid supports are of great interest since they generally yield the best activity stabilities (10). Nevertheless two difficulties may be encountered: low levels of activatable or activated surface groups on the support and denaturation of enzyme if covalent coupling is accomplished through functional groups of the enzyme which are essential to its catalytic activity.…”

Section: Literature Cited Introductionmentioning

confidence: 99%

“…However, a merit of the windowsweep chronopotentiometry is the simplicity of the procedure for the correction of charging current. Chronopotentiograms are also obtained coulostatically (10). In this mode, constant-sized charge pulses at constant time intervals (equivalent to a constant current) are applied and the change of electrode potential is monitored as a function of the cumulative time.…”

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confidence: 99%