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New platforms for electroanalytical research, and applications of electroanalysis involving electrochemical signal transduction at solid electrodes for detection and sensing of a great variety of chemically, biologically and environmentally important analytes, have been developed and employed for more than five decades [1].

Polarography is an electroanalytical technique based on recording of current–voltage (i−E) curves using electrolysis, with a dropping mercury electrode (DME) as an indicator electrode. This technique has been invented in 1922 by Heyrovsky [1]. For his invention, he was awarded in 1959 the Nobel Prize. According to the Analytical Chemistry, polarography has been over the period from 1950 to 1970 one of the five most frequently used analytical techniques. The scope of its worldwide applications suffered a decline more recently, because of the wide range of separation techniques in organic analysis. Similarly, the use of atomic absorption (AA) and related techniques became predominant in the determination of metal ions. As reflected by the number of references in the Tables, polarography is currently used in those laboratories, where limited budgets do not allow acquiring of more expensive instrumentation, as needed in AA and modern separation techniques.

The choice of an appropriate technique for the determination of a drug or a mixture of drug compounds is mainly governed by the sample matrix complexity, the analyte concentration, and the sample treatment time. Compared to optical, mass, and thermal methods, electrochemical techniques are especially attractive because they offer unique detection capabilities with remarkable selectivity and sensitivity for a moderate cost [1–17]. The final selection of an analytical technique depends on the intrinsic structure and physicochemical properties of the studied analyte. Potentiometric electrodes have been described for the selective determination of pharmaceuticals, but voltammetric methods are most generally developed due to their inherent high sensitivity and versatility provided that the studied drug compound is electroactive.

Analytical chemistry, specifically electroanalytical chemistry, plays an important role in many branches of chemistry, biochemistry, pharmacy, food productions, life science, environment, etc. Many decisions are based on the results of quantitative analyses, and it is important to be aware of the quality of the results whenever analytical or electroanalytical methods are used. Analytical properties are quality indicators for a variety of systems, objects, tools, and outputs involved in chemical or biochemical measurements that allow one to compare and validate both analytical processes and the results that they provide. The objective of any analytical measurements is to obtain consistent, reliable, and accurate data. Validated analytical methods play a major role in achieving this goal. Analytical method validation is a major issue in the pharmaceutical industry for controlling drug quality, development, and registration. Simply, it is used to justify the analytical method used, in other words, to show that the method accomplishes what is claimed or intended. Validation is required for the development of new analytical methods, methods submitted as a part of a new drug application, bioequivalence and bioavailability studies, and for the analysis of drugs as raw material or in their dosage forms. Likewise, all laboratory tests must be validated before being introduced for patient testing to insure that the values reported will meet clinical expectations with a desired degree of reliability. Revalidation should be required, to a less or greater degree, following any change in reagents, supporting electrolytes, instruments, or experimental conditions. Evaluation and validation of an electroanalytical method performance is required to assess the degree of error expected due to inaccuracy and imprecision and to confirm that the degree of error meets the anticipated laboratory or clinical requirements. The procedures recommended for method validation differ with the type of test and the anticipated use. Experiments must be designed so that the correct data are obtained. The appropriate statistical methodologies should be used to correctly estimate errors with sufficient precision and to make the right decision about method’s validity.

Electrochemical detectors can be very well adapted to hydrodynamic conditions such as those encountered in liquid chromatography (LC), in capillary electrophoresis, or in flow injection analysis (FIA) applied to drug compound analysis [1–10]. Detectors with low cell volume based on conductivity [11–13], potentiometry [14, 15], amperometry (AD) [1–10], or pulsed amperometry (PAD) [16, 17] can be located online in close proximity, in a post-column configuration, to a liquid chromatographic setup or inserted as microelectrodes close to a capillary end [18, 19]. A miniaturized electrolysis cell can also be part of an online in a FIA system or of a pre- or post-LC column coupled to a mass spectrometer for electrochemical product generation and characterization [20–23]. Trends are directed to miniaturize the entire flow analytical system (e.g., lab on chip) and microfabricated electrochemical sensors as ideally suited for such configurations [24–26]. This chapter describes some basic concepts of most used and commercially available amperometric detectors and reactors coupled to LC or FIA. Examples are collected from authors’ laboratory, and a nonexhaustive literature survey of applications to the assay of molecules of pharmacological interest is provided.

Amongst the variety of electrochemical methods and techniques available for drug analysis, voltammetry, i.e. the recording of the current, as a function of applied potential, has become the most important and widespread.

Electroanalysis in biomedical and pharmaceutical sciences , Electroanalysis in biomedical and pharmaceutical sciences , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

A vast number of instrumental techniques are currently available for the selective and sensitive determination of pharmacologically active compounds. Spectroscopic and electrochemical methods and hyphenated techniques such as liquid chromatography and capillary electrophoresis are nowadays routinely used at the academic level and in the pharmaceutical industry.

The proper medication dosage in pharmaceutical formulations and in physiological fluids is of primary importance in health care. Qualitative and quantitative data are needed for pharmaceuticals in order to check for appropriate drug content and to detect any counterfeit or industrial production error. The determination of the active drug compound in plasma is of interest regarding its bioavailability and its therapeutic efficacy. The determination of drug residues and growth factors in animal products (milk, meat, honey…) and in surface water is also essential in terms of environmental and health concerns.