Online fluorescence monitoring

Most studies about MAE of PAHs from solid samples have been conducted using closed-vessel systems and only a few with open-vessel focused microwave devices. Because open-vessel systems operate at atmospheric pressure, the extraction vessel has been used as a reactor in order to perform online piu ifica-tion pretreatments of the total extracts (reagents can be added readily to the medium) or introduce the extracts directly into the determination instrument, as in the focused microwave-assisted extractor with online fluorescent monitoring, which provides a matrix-independent approach to the extraction of PAHs. 

At the top end of the program monitoring scale is the use of online fluorescence tracing systems, whereby tracer dye polymers form part of the water treatment program and their concentration can be measured online at various locations throughout the boiler plant system. Much less expensive, handheld fluorometers are now available to conduct the same type of analysis at the laboratory bench or on the boiler house firing-floor. These tracer dye polymers can be used to determine ... 

Cell components or metabolites capable of recognizing individual and specific molecules can be used as the sensory elements in molecular sensors [11]. The sensors may be enzymes, sequences of nucleic acids (RNA or DNA), antibodies, polysaccharides, or other reporter molecules. Antibodies, specific for a microorganism used in the biotreatment, can be coupled to fluorochromes to increase sensitivity of detection. Such antibodies are useful in monitoring the fate of bacteria released into the environment for the treatment of a polluted site. Fluorescent or enzyme-linked immunoassays have been derived and can be used for a variety of contaminants, including pesticides and chlorinated polycyclic hydrocarbons. Enzymes specific for pollutants and attached to matrices detecting interactions between enzyme and pollutant are used in online biosensors of water and gas biotreatment [20,21]. 

Several approaches have been reported for the screening of polymerase activity, for example radioisotope assays such as scintillation proximity assays [56, 57] or fluorescence-based assays [58-61], Most of these assays, however, suffer from use of tedious procedures, the use of radioisotopes, or use of expensive reagents for fluorescence signal generation. A convenient means of online monitoring of DNA polymerase activity has recently been presented by Andreas Marx and Daniel Summerer [62]. Their technique involves a DNA template that forms a stable hairpin structure labeled at two positions ... 

Hannemann et al. (2007) designed a versatile cell that is compatible with both transmission and fluorescence XAFS spectroscopy, XRD, and both gas and liquid environments it also allows for online monitoring of... 

The tests utilized to measure these contaminants and degradation by-products include infrared (IR) spectroscopy, electronic particle counting (PC), Karl Fischer titration (KFT), atomic emission spectroscopy (AES) and X-ray fluorescence (XRF) spectroscopy. These methods are available in the form of off-line or at-line benchtop instruments and online/in-line sensors. Most off-line instruments are automated to provide several hundred analyses per day by a single technician. At-line instruments and sensors permit immediate results and diagnostic capabilities. Online sensors can be integrated into machinery control systems to provide real-time monitoring capability. 

Seibert, M., Makarova, A., Tsygankov, A., and Rubin, A.B. A Fluorescence Technique for Online Monitoring of the Physiological State of Hydrogen-Producing Microorganisms, Patent application submitted. 

Lada, M. W., et al.. High temporal resolution monitoring of glutamate and aspartate in vivo using microdialysis online with capillary electrophoresis with laser-induced fluorescence detection. Anal. 

Another area in which PIMs show considerable promise is chemical analysis. The use of PIMs in the construction of ISEs and optodes is well established, but their potential use in analytical separation is only starting to be explored. PIMs are particularly useful in solid-phase extraction (SPE) for preconcentration of analytes [17,18]. Also, Eonths et al. have used a PIM containing Aliquat 336 as the carrier for the preconcentration of Cr(VI) prior to its determination in the membrane by energy-dispersive X-ray fluorescence spectrometry [47]. Flat-sheet PIMs can also be conveniently incorporated into separation modules for use in online analytical techniques such as flow injection analysis. For example, a D2EHPA-based PIM has been used in a separation module incorporated into a flow injection analysis system for the determination of Zn(II) [35]. This new approach has interesting implications for use in automated analysis, particularly in held instruments for the continuous monitoring of pollutants. 

One of the main advantages of CE over gel electrophoresis is that the separation is monitored by online, on-column, or end-column detection. In the most frequently employed UV absorption photometric detection, a small part (less than 1mm) of the capillary serves as a detection cell. Micromolar concentrations of proteins are detectable using the low UV detection wavelength of 200-220 nm. A higher sensitivity, up to nanomolar concentrations, is achieved with fluorescence, particularly laser induced fluorescence (LIE) detection. The disadvantage of the LIE detection of proteins is the necessity for their derivatization using a fluorogenic label. The native fluorescence of proteins, mostly due to the presence of aromatic amino acids residues, tryptophan, and tyrosine, can be utilized only when low UV laser... 

Methods for detection of biomass can be divided into direct and indirect methods (Table 2). Most online probes for direct monitoring of cell mass are based on optical principles, including light absorbance, light scattering, and fluorescence. Although such sensors may work well in specific cases, often... 

---