Solvent Extraction Spectrofluorimetry

Fluorescence spectrometers are equivalent in their performance to single beam UV-visible spectrometers in that the spectra they produce are affected by solvent background and the optical characterises of the instrument. These effects can be overcome by using software bnilt into the Perkin-Elmer LS-5B instrument or by using application software for use with the Perkin-Elmer models 3700 and 7700 computers. 

The model LS-2B is a low-cost, easy to operate, filter fluorimeter that scans emission spectra over the wavelength range 390-700 nm (scanning) or 220-650 nm (individual 

In many cases visible flnorescence techniqnes are less subject to interference by other polymer additives present in a polymer extract than are UV methods of analysis. Therefore, 

Aromatic amines and phenols are among the few classes of compounds in which a large proportion of their members exhibit sensible fluorescence other types of visible fluorescing compounds include some benzoquinones, hydroxyl methoxy benzophenones, coumarin derivatives and UV absorbing polymer additives. 

Kirkbright and co-workers [86] carried out a study of the general feasibility of the fluorimetric or phosphorimetric determination of stabiliser compounds after their extraction from polymers with organic solvents. They examined the fluorescence and phosphorescence characteristics of 29 common antioxidants and UV absorbers in an organic solvent medium at room temperature and -200 °C, respectively, and they report the fluorescence and phosphorescence spectral characteristics in a mixture of diethylether, isopentane, ethanol and chloroform and the calibration data phosphorescence detection limits and phosphorescence life-times. 

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The element may be determined at 196.0 nm by A AS, using a nitrous oxide-acetylene flame (which is more transparent than air-acetylene at this low wavelength), or by AFS in a variety of flames.46,47 The detection limit of both techniques for selenium is around 1 mg 1 1, too low to be useful for environmental analyses. The element is therefore invariably determined by hydride generation techniques, coupled to AAS or AFS detection, as discussed in Chapter 6, section 2, or by furnace AAS, or occasionally by solution spectrofluorimetry using 2,3-diaminonaphthalene as a reagent. If direct flame AAS or AFS are to be used for some reason, then pre-concentration by solvent extraction is necessary.1 However, this approach is rarely used nowadays. 

Shpol skii spectrofluorimetry has been used for the determination of PAHs in crude enviromnental sample extracts with minimum sample cleanup. This technique gives a vibrationally resolved fluorescence spectrum of samples dissolved in a suitable solvent (usually an -alkane) at cryogenic temperatures, e.g., 26 K. It combines the selectivity of an infrared spectrum with the sensitivity of fluorimetry, though the sensitivity suffers considerably from the presence of large amounts of interfering substances such as fatty components in crude extracts since these give a poor-quality matrix with a high sample absorbance. 

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