Self-quenching time analyses

Two self-calibrated methods are available that do not rely on the knowledge of of a reference compound. Horrocks et al. described an accurate method based on the measurement of triplet triplet absorption by flash photolysis, in combination with Stem Volmer analysis of fluorescence quenching (Section 3.9.8).238 Bromobenzene was used as a heavy-atom quencher of the fluorescence of 9-phenylanthracene. More recently, time-resolved measurements of delayed fluorescence (Section 2.2.4) were analysed to give accurate triplet quantum yields.239... 

An aqueous sample may be added to the cocktail directly, after minor prior processing, or at the end of a radiochemical separation procedure. Direct addition is the equivalent of gross activity counting discussed in Section 7.2.4 except that some spectral analysis may be possible. Alpha particles can be differentiated from beta particles by deposited energy, pulse shape, and decay time. Self-absorption is of no concern. Quenching and luminescence, discussed in Section 8.3.2, often occur. Identification by maximum beta-particle energy is approximate, and requires comparison to radionuclide standards. 

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