Biomedical trace analysis detectability

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 the modem world, trace analysis plays an important role in such areas as ecology, chemical engineering, food processing, biomedical analysis, and dmg chemistry. Advanced, sensitive, and precise analytical methods allow identification and quantification of different compounds, both organic and inorganic, including macro-molecular complexes. All these methods present very good detection and quantification levels, up to parts per trillion (ppt) or parts per quadrillion (ppq). 

The determination of molecular formulas via accurate mass measurements relies on isotopic masses accurate to at least 1 in 10 [10]. Elemental trace analysis is required for the detection of radioactive nuclides in the environment, of transition metals such as Pt in exhaust fumes from automobiles [11], and in the quality control of low-sulfur fuels for the same. All electronic devices demand for high-purity semiconductors and the properties of alloys are critically influenced by trace elements [12]. Age determinations from isotope ratios are applied in archeology, paleontology, and geology [4,13,14]. More recently, elemental MS and biomedical MS are jointly employed to unveil the presence and preferably location of metals in proteins or DNA as well as their lateral distribution in tissues [15-18], a field of research basically going back to seminal work by Houk in 1980... 

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... 

Plasma emission spectrometry, especially ICP- and DCP-sources, has a fixed place in modern trace element analysis. In spite of the relatively small number of relevant elements detectable by these techniques for the biomedical and environmental fields of application, plasma emission spectrometry can deliver a lot of possibly important information. The main advantages are the multielement character of the technique (sequentially or simultaneously), nearly chemical interference free measurements, control of physical interferences, a relatively high level of accuracy and precision, high specificity, fast multielement determinations (especially in case of a simultaneous device), low sample consumption and in general a wide range of detectable elements (Table 13). 

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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