Intrinsic fluorescence detector

A third type of detector is the intrinsic or native fluorescence detector that utilizes native fluorescence properties of amino acids. The sensitivity of this detector is between UV/PDA and LIF detection. The advantage of this technique over pre-labeling is that there is no pre-labeling step required therefore, the sample preparation is relatively simple, and the sensitivity is improved over UV/LIF. However, the intrinsic fluorescence detection relies on the presence of Tryptophan (Try), Tyrosine (Tyr), Phenylalanine (Phe), and this detector has just become commercially available. 

Eluorescence or laser-induced fluorescence (EIF) detectors can be used in CEC to obtain higher sensitivities compared with UV detection. However, these detection systems are only limited to analytes that are intrinsically fluorescent or can be derivatized to fluorescent analogues. 

As noted in the preceding table, elution of PAHs is detected by UV absorbance at two different wavelengths 280 nm and 365 nm. Fluorescence detectors are also applicable to the HPLC analysis of PAHs (9, 19). The UV detector monitors the sample simultaneously at two wavelengths, aiding in compound identification. For a specific compound, the ratio of absorbances at two different wavelengths is an intrinsic physical characteristic. Therefore, it is possible, in principle, to identify a sample analyte by this characteristic ratio. The chromatographic retention time of each of the specific peaks observed in the sample eluate is compared with those of known standard compounds for tentative analyte identification. For quantitation, peak areas of each standard, at each of six... 

Disadvantages of semiconductors are primarily size and cost related. For x-ray fluorescence applications in patients, detectors have been limited in size to 25 mm diameter by 5 mm thick Si(Li) detectors and 25 mm diameter by 10 mm thick intrinsic germanium detectors. These detectors typically cost 8000- 12,000 with this price including the detector, cryostat, and pre-amplifier. 

Because of the underlying photophysics, fluorescence lifetimes are intrinsically short, usually on the order of a few nanoseconds. Detection systems with a high timing resolution are thus required to resolve and quantify the fluorescence decays. Developments in electronics and detector technology have resulted in sophisticated and easy to use equipment with a high time resolution. Fluorescence lifetime spectroscopy has become a popular tool in the past decades, and reliable commercial instrumentation is readily available. 

Post-column derivatization Is widely used in liquid chromatography [30, 31], the potential of which is thereby Increased. It affords a number of objectives (a) indirect Improvement of the analyte s intrinsic sensitivity In a given detector (the resultant reaction product absorbs or emits more intense fluorescence than the parent analyte isolated in the column, even after preconcentration) (2) facilitating detection through removal of the excess of derl-vatizing reagent or thanks to the detector s blindness to the separated analytes (c) providing an identification test for one or several of the analytes in a complex mixture. 

Amplitude-phase crosstalk is intrinsically low in frequency-domain instraments that use gain-modulated PMTs as detectors and mixers [166]. Results presented in [98, 346] show that optical properties can be obtained with an accuracy comparable to that of TCSPC-based instraments. The modulated-PMT technique is somewhat less efficient than TCSPC and does not work well at extremely low photon rates. Nevertheless, the sensitivity is well within the range required for fluorescence detection in DOT. 

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