Electrochemical detection biomedical analysis

For biomedical trace analysis, three types of detectors are currently popular—the absorption photometric detector, the fluorescence detector, and the electrochemical detector. Although there are other kinds of detectors, only these have the ability to detect 10 -10 g of analyte, the kind of detectability needed in biomedical analysis, especially where small amounts of drugs are concerned. 

In spite of the overall importance of biological amines, the methodological difficulties have confined the determinations of such compounds to specialized biomedical laboratories. While the derivatization methods still appear to be far from being optimized, the high-sensitivity determinations done with expensive equipment (e.g., a mass spectrometer) are outside the reach of many laboratories. More recently, HPLC has been under development as a very attractive alternative for this class of compounds fluorometric and, in particular, the electrochemical detection in combination with HPLC have enjoyed much attention [417]. Although the GC methodological approaches to the analysis of biological amines may yield to HPLC in time, a fair number of GC studies are still reported in the literature. 

Baldwin RP (1999) Electrochemical determination of carbohydrates Enzyme electrodes and amperometric detection in liquid chromatography and capillary electrophoresis. Journal of Pharmacological and Biomedical Analysis 19 69-81. 

One of the most active areas of electrochemical research and development in the last decade has been the use of electrochemical detectors for flowing stream analysis. Of particular interest is the analysis of complex solutions containing several chemical species. The use of high performance chromatography coupled to electrochemical detection (LCEC) is an important development in this regard. In most applications of conventional LCEC, such as in clinical, biomedical or organic analysis, discrete samples are analysed. 

Wang, A. Fang, Y. Applications of Capillary Electrophoresis with Electrochemical Detection in Pharmaceutical and Biomedical Analysis. Electrophoresis 2000 21, 1281-1290. 

With the introduction of modern electronics, inexpensive computers, and new materials there is a resurgence of voltammetric techniques in various branches of science as evident in hundreds of new publications. Now, voltammetry can be performed with a nano-electrode for the detection of single molecular events [1], similar electrodes can be used to monitor the activity of neurotransmitter in a single living cell in subnanoliter volume electrochemical cell [2], measurement of fast electron transfer kinetics, trace metal analysis, etc. Voltammetric sensors are now commonplace in gas sensors (home CO sensor), biomedical sensors (blood glucose meter), and detectors for liquid chromatography. Voltammetric sensors appear to be an ideal candidate for miniaturization and mass production. This is evident in the development of lab-on-chip... 

Numerous methods have been reported for the analysis of cyanide and thiocyanate in biomedical samples, mostly for the determination of cyanide levels in smokers and fire victims rather than cases of deliberate poisoning. These methods include visible, ultraviolet (UV) and fluorescence based spectrometric methods, electrochemical methods using ion selective electrodes, and GC with nitrogen-phosphorus detection (NPD), electron capture detection (ECD), or MS. It is not intended to cover all of these but focus mainly on chromatographic methods. 

In the present research work, serum and urine samples were selected for metabolite analysis. Only sample dilution and concentration enhancement were integrated into the microchip-CE devices developed. However, for variable and complex biomedical samples, which require additional sample pretreatment and present a bigger challenge than normal sample. Although the use of UV detection is universal and applicable for most analytes, its sensitivity is insufficient for the detection of trace analytes. Other detectors such as chemiluminescence and electrochemical detector can be developed coupled with microchip-CE. 

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