Microchemical detection methods

Just like the physical and microchemical methods of detection, the indirect, biological-physiological detection procedures are very selective when apphed to thin-layer chromatography. Here it is not chemical functional groups or particular physical properties that are selectively detected but effects on highly sensitive biodetectors . The following detection techniques have been employed ... 

Owing to its use as a vermin-killer and to its importance in toxicology, a great deal of attention has been given to methods for the isolation of strychnine from biological materials and the detection of minute quantities. For critical reviews of such methods see Ainsworth Mitchell, Steyn,ii Ward and Munch. A microchemical method for the differentiation of str3 chnine and brucine has been described by Martini. i... 

Further improvement of microchemical methods for proteinaceous media was based on immunological techniques. The high specificity of the antigen-antibody reaction enables the discrimination of the same protein coming from different species, or the detection of multiple antigens in the same sample. Application to the analysis of artwork has been reported in two types of immunological techniques immunofluorescence microscopy (IFM), and enzyme-linked immunosorbent assays (ELISA) [31]. 

Bayer s microchemical method, mentioned in connexion with rubidium (p. 199) and caesium (p. 210), serves to detect one-hundredth of a microgram of silver. 

Chitin is present - in green algae, but not in bacteria and Actinomycetes, whilst there is still controversy about its presence in the yeasts (Saccharomycetes). Using microchemical methods of detection, Roelofsen and Hoette found chitin in a variety of filamentous and non-filamentous yeasts, thus... 

Fujiwara, T., K. Murayama, and T. Imdadullah Kumamaru, 1994. Automated method for the selective determination of gold by online solvent extraction and reversed micellar-mediated luminal chemiluminescence detection. Microchem. J. 49 183-193. 

Depurination, alteration of nucleic acids by, 945 Desalting procedures in sample preparation, 14-15 Detection, 205-218 measurement of radioactivity, 345-355 mictdbioiogical methods, 218 microchemical methods, 211-218... 

In principle it is possible to employ physical, microchemical and biological-physio-logical methods for detection in TLC (Fig. 2). 

Physical detection methods are based on inclusion of substance-specific properties. The most commonly employed are the absorption or emission of electromagnetic radiation, which is detected by suitable detectors (the eye, photomultiplier). The / -radiation of radioactively labelled substances can also be detected directly. These nondestructive detection methods allow subsequent micropreparative manipulation of the substances concerned. They can also be followed by microchemical and/or biological-physiological detection methods. 

This volume is divided into two parts which encompass about the same amount of material as Volume 1 a. Thus Part I begins with specific detection methods including the known photochemical, thermochemical and electrochemical activation methods. Here microchemical reactions are described that are carried out without the use of reagents. Detection involves the use of light, heat and electric current. 

The microchemical detection methods are the most economical methods and the simplest for the chemist to carry out. No expensive apparatus is required and in certain circumstances they can be combined with the two detection methods mentioned above. 

Three types of detection methods for TLC may be distinguished, namely physical, microchemical and biological-physiological. The more common detection methods for polymer additives in TLC are given in Figure 4.8. Detection is an off-line process, thus several detection techniques may be used one after the other. 

Jackman, R.J., Floyd, T.M., Schmidt, M.A., Fensen, K.F., Development of methods for on-line chemical detection with liquid-phase microchemical reactors using conventional and unconventional techniques. Micro Total Analysis Systems, Proceedings of the 4th pTAS1 Symposium, Enschede, Netherlands, May 14-18, 2000, 155-158. 

Macroscopic methods for chemical analysis essentially take either all of the particulate matter sampled or a significant protion of it for bulk analysis. Traditionally, this has been approached by the application of standard microchemical techniques of wet chemistry. The unique analytical requirement for aerosol particle samples is the microgram quantities collected. The analytical methods adopted must be capable of detecting these quantities in... 

Chromatographic techniques are the main methods that have been used to separate, detect, and identify organic components of FDR.152 162 Other methods considered include molecular luminescence,163 infrared spectroscopy,164 Raman spectroscopy,165 electron spin response spectrometry,166 microchemical crystal tests,167 168 ultraviolet spectroscopy/nuclear magnetic resonance/polarography.169... 

As described above, the design, fabrication, control, and detection methods were established for integrated microchemical systems. We have applied the techniques to a variety of chemical systems. 

In principle it is possible to employ physical, microchemical and biological-physio-logical methods for detection in TLC (Fig. 2).---------------------------------... 

Protein expression encompasses an enormous dynamic range. Since rare proteins cannot be amplified by any type of PCR method, sensitive detection is critical to proteome projects. Fluorescence methods deliver streamlined detection protocols, superior detection sensitivity, broad linear dynamic range and excellent compatibility with modem microchemical identification methods such as mass spectrometry. Two general approaches to fluorescence detection of proteins are the covalent derivatization of proteins with fluorophores or noncovalent interaction of fluorophores through direct electrostatic interaction with proteins. One approach for quantifying fluorescence is to use a photomultiplier tube detector combined with a laser... 

G. Klein and F. Schusta (2) have described methods for the microchemical detection of the alkaloid. 

Wetted fibers on-chip have only recently been attempted and show great promise. Like embedded fibers, the wetted fibers require very sophisticated microfabrication techniques. Microfluidics has seen the rapid development of new methods of fabrication and of components such as microchannels that serve as pipes and other structures that form valves, mixers, and pumps that are essential elements of microchemical factories on a chip. Wetted fibers will require easier ways of inserting and removing the fibers from the chip as well as simpler methods of preparing the fiber tips with biomolecules for detection. 

Today, in situ techniques are generally employed for the detection of chromatogram zones and also for their identification and quantification (Fig. 1). Thereby, like an analytical disk (1), the information stored in the chromatogram can be used for different detection and identification methods, even successively, because the processes of chromatographic development and detection or identification are independent both in time and space. That means, after recording, e.g., a UV absorption scan, an FTIR- or Raman-spectrum can be recorded, and these methods can be followed by a suitable microchemical reaction or mass spectometry to provide additional information. 

Physical, microchemical and/or microbiological or biochemical detection methods, preparation of pre- or postchromatographic derivatization reagents, derivatization technique, stabilization reagents, heating... 

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