Optical detection systems chemiluminescence

Samples are introduced into the capillary by either electrokinetic or hydrodynamic or hydrostatic means. Electrokinetic injection is preferentially employed with packed or monolithic capillaries whereas hydrostatic injection systems are limited to open capillary columns and are primarily used in homemade instruments. Optical detection directly through the capillary at the opposite end of sample injection is the most employed detection mode, using either a photodiode array or fluorescence or a laser-induced fluorescence (LIF) detector. Less common detection modes include conductivity [1], amperometric [2], chemiluminescence [3], and mass spectrometric [4] detection. 

A DNA optical sensor system was proposed by Cass and co-workers [35] based on the combination of sandwich solution hybridization, magnetic bead capture, flow injection and chemiluminescence for the rapid detection of DNA hybridization. Sandwich solution hybridization uses two sets of DNA probes, one labelled with biotin, the other with an enzyme marker and hybridization is performed in solution where the mobility is greater and the hybridization process is faster, rather than on a surface. The hybrids were bound to the streptavidin-coated magnetic beads through biotin-streptavidin binding reaction. A chemiluminescence fibre-optic biosensor for the detection of hybridization of horseradish peroxidase-labelled complementary DNA to covalent immobilized DNA probes was developed by Zhou and co-workers [36]. 

Sensitive Optical Detectors. More sensitive optical techniques that have been used with CE include fluorescence, refractive index, chemiluminescence, Raman spectrophotometry, and circular dichroism. The most sensitive optical detection method used in CE is laser-induced fluorescence (LIE), which is capable of detection limits in the 10 to 10" mol (or better) range. This detection mode is easily accomplished with analytes that are either easily labeled with a fluorescent substrate (e.g., intercalators for double-stranded DNA) or are naturally fluorescent (e.g., proteins or peptides containing tryptophan). CE systems have also been interfaced with mass spectrometers, and electrochemical detection methods have been developed, although such detectors must be isolated electrically from the electrophoretic voltages. 

A unique chemiluminescence photon-counting system, designed specifically for measurement of stress-enhanced polymer reactions, was used for the studies described here. This system Includes a miniature tensile stress device, a controlled environment chamber and a luminescence detection system and associated optics Integrated Into a single unit. 

Early optically detected microwave transition linewidth studies (Pratt and Broida, 1969) suggested that CN A2II(u = 10) —> B2E+(u = 0) collision-induced transitions through perturbed levels occur at gas-kinetic collision rates, faster than pure rotational relaxation. The pressure dependence of chemiluminescence in the Ba + N2O system also implied BaO b3II(u = 10) —> A1E+(u = 1) collisional transfer through spectroscopic doorways (Field, et al., 1974). 

Some of these less used systems have limited applications in specific areas and combine HPLC with, for instance, chemiluminescence techniques [48], viscometry [49], optical activity measurement [50], piezoelectric crystals for mass scanning [51], atomic absorption and emission spectrometry [52-54], photoacoustic monitors [55], nuclear magnetic resonance [56], electron spin resonance [57], Raman [58] and photoconductivity measurement [59]. Details on these and other innovative detection systems are presented in the review by Bruckner [60]. 

A schematic block diagram illustrating an entire DP-SCD detection system is shown in Fig. 2. An analytical system consists of a gas chromatogr h equipped with a split/splitless iigector with the option of a Pressurized Liquid Injection System (PLIS), wifli or without low diermal mass gas chromatogr q)hy apparatus, for sample introduction and sulfur speciation (if required) an electrically heated burner with an interface that controls the burner gas flows and temperature and a detector that contains a chemiluminescent reaction cell, ozone generator, optical filter, amplifier, and electronics. Lastly, a vacuum pump is used to keep file reaction cell under low pressure conditions to prevent loss of chemiluminescent species and to reduce collisional quenching. 

Cell responses to physical or chemical cues are measured in microfluidic devices primarily via optical or electrochemical means. Huorescence is the most widely used optical detection technique, because absorbance detection (commonly used for macroscale assays) is of limited value in microchannels because of the short path lengths. Fluorescence detection, characterized by its unparalleled sensitivity, is easy to implement in microfluidic systems. Chemiluminescence and bioluminescence also offer low detection limits and have less background noise than fluorescence [8]. Electrochemical detectors are even more easily integrated with microfluidic devices and often are much less expensive than optical systems. However, fabrication of electrodes in microchannel devices is a technical challenge, and the electrical fields used in detection can interfere with on-chip processes such as electrophoresis. Electrochemical techniques include potentiometry, amperometry, and... 

The analytical detectability applying a CL method should, in principle, be comparable to that obtained using radioactive labels, without all the disadvantages related to the use of isotopic labeling. In fact, assuming reasonable values for the quantum efficiency of the chemiluminescent reaction (Cl 0.01), for the overall photon collection efficiency of the optical system-CCD camera assembly (T) 0.01%), and for the intensity of the lowest detectable CL signal (about... 

Other detection methods have been used in optical MIP sensing systems. An MIP-based chemiluminescent flow-through sensor was developed for the detection of 1,10-phenanthroline (Lin and Yamada 2001). A metal complex was used to catalyze the decomposition of hydrogen peroxide and form the superoxide radical ion that can... 

Due to its simple optical devices, wide linear range of response and many well characterized CL systems, chemiluminescence (CL) is uniquely suited to on-line detection for /t-TAS. Some reports have shown that CL is an alternative promising detection method for capillary electrophoresis microchip. In the present work, some glass microchips were designed based on the flow injection and electroosmotic flow (EOF)-chemiluminescent devices and applied to determine transition metal ions and organic compounds. 

Hatta-Ohashi Y, Hayasaka N, Takahashi T, Shigeyoshi Y, Suzuki H. Application of a luminescence microscope with novel optical system for detection of the gene expression pattern of individual cells. In Szalay AA. Hill PJ, Kricka LJ, Stanley PE. eds. Bioluminescence and Chemiluminescence 2007 Singapore World Scientific. 2007 45-8. 

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