Fluorescence-phosphorescence detector

Fluorescence - phosphorescence detector selective yes to--10 < lo- flow (temperature)... 

Fluorometry and Phosphorimetry. Modem spectrofluorometers can record both fluorescence and excitation spectra. Excitation is furnished by a broad-band xenon arc lamp foUowed by a grating monochromator. The selected excitation frequency, is focused on the sample the emission is coUected at usuaUy 90° from the probe beam and passed through a second monochromator to a photomultiplier detector. Scan control of both monochromators yields either the fluorescence spectmm, ie, emission intensity as a function of wavelength X for a fixed X, or the excitation spectmm, ie, emission intensity at a fixed X as a function of X. Fluorescence and phosphorescence can be distinguished from the temporal decay of the emission. 

Colorless substances absorb at wavelengths shorter than those of the visible range (the UV range normally amenable to analysis X = 400...200 nm). Such compounds can be detected by the use of UV-sensitive detectors (photomultipliers. Sec. 2.2.3.1). Substances that absorb in the UV range and are stimulated to fluorescence or phosphorescence (luminescence) can be detected visually if they are irradiated with UV light. 

Fluorescence is much more widely used for analysis than phosphorescence. Yet, the use of fluorescent detectors is limited to the restricted set of additives with fluorescent properties. Fluorescence detection is highly recommended for food analysis (e.g. vitamins), bioscience applications, and environmental analysis. As to poly-mer/additive analysis fluorescence and phosphorescence analysis of UV absorbers, optical brighteners, phenolic and aromatic amine antioxidants are most recurrent [25] with an extensive listing for 29 UVAs and AOs in an organic solvent medium at r.t. and 77 K by Kirkbright et al. [149]. 

The Phosphoroscope. This is a simple mechanical device which allows the separation of long-lived emissions (phosphorescence) from short-lived emissions which consist of scattered light and fluorescence. It is a disc or drum in which there are holes or slots placed in such a way that the excitation and emission beams reach the sample and the detector respectively at different times. With the fastest practicable rotation velocities of the phosphoroscope, the cut-off time is of the order of 1 ms. 

Since the heterocyclic-substituted platinum 1,2-enedithiolates are dual emitters with only one emission that is oxygen quenched, ratiometric oxygen analysis is possible (see Fig. 3) (21, 29). While fluorescence and phosphorescence intensities vary with changes in optical clarity, fluctuations in the source and detector, and photobleaching of the emitter, the intensity ratio of a dual emitter (phosphorescence-fluorescence) does not. As such, the 3I/1I intensity ratio can be used in place of I, in Eq. 3 to generate Eq. 7 and 8 (29-31, 69). 

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