Solid electrodes, liquid chromatography

Amperometric sensing of selected species in liquids is widely extended with an enormous variety of materials and applications, which include electrochemical detection coupled with high-performance liquid chromatography and flux injection analysis. In these cases, high sensitivity and high reproducibility are required. These properties are conditioned by electrode fouling associated to formation of solid deposits and adsorbates on the electrode surface. As a result, the electrode experiences memory effects with concomitant loss of analytical performance. 

Electrochemical detectors were reported used by 21% of the respondents to the detector survey (47). Electron transfer processes offer highly sensitive and selective methods for detection of solutes. Various techniques have been devised for this measurement process, with the most popular being based on the application of a fixed potential to a solid electrode. Potential pulse techniques, scanning techniques, and multiple electrode techniques have all been employed and can offer certain advantages. Two excellent reviews of electrochemical detection in flowing streams have appeared (59,60), as well as a comprehensive chapter in a series on liquid chromatography (61). 

H. W. van Rooijen and H. Poppe, An Electrochemical Reactivation Method for Solid Electrodes Used in Electrochemical Detectors for High-Performance Liquid Chromatography and Flow Injection Analysis. Anal. Chim. Acta, 130 (1981) 9. 

This paper investigates the differential pulse polarographic, dc and square wave voltammetric determination of selected antibiotics, antibacterials and anticonvulsants at mercury and solid electrodes. The results of these determinations are compared and contrasted with rival analytical methods based on high performance liquid chromatography with ultraviolet detection. 

Benzoic acids (BAs), and their respective sodium, potassium, and calcium salts are the most commonly used preservatives in foodstuffs. Most often high-pressure liquid chromatography (HPLC) methods [71] are used for the determination of benzoates in food and beverage products. Several attempts have been made [72, 73] for developing the benzoate-selective electrode as a sensor applicable in a simple cost-effective measuring procedure. Alizadeh et al. [74] developed a solid contact electrode on a platinum-based sensing element. For the preparation of the selective benzoate measuring film, pyrrole was electropolymerized in the presence of sodium benzoate and sodium dodecyl benzenesulfonate. The slope of the calibration curve of the electrode was 55.4mV/decade in the benzoate concentration... 

ISEs are well suited for flow measurements because the instrumentation and signal handling are simple, the measurement is almost independent of the liquid flow-rate, the linear dynamic range is broad, the temperature dependence is not very pronounced and the measurement is selective (the selectivity is, however, a drawback in applications to chromatography). The experimental conditions are readily adjusted and often only consist of ionic strength and pH maintenance. ISEs with solid membranes usually exhibit better performance than liquid membrane electrodes and gas probes, because their response is faster and they are mechanically stronger. The most difficult problem is passivation of the electrodes in some media, for example, biological fluids or surface and waste waters. 

Gas chromatography (GC) Separation methods that make use of a gaseous mobile phase and a liquid or a solid stationary phase. Gas electrode An electrode that involves the formation or consumption of a gas during its operation. 

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