Color quenching in "environmentally friendly" cocktails.

Fluorescent and colored compounds used in molecular biology labs may generate color quench in wipe test samples taken from such labs. The ability of conventional chemical quench curves to correct for color quench caused by fluorescent and colored compounds in "environmentally friendly" cocktails has not been reported. Series of colored samples spiked with 3H or 14C were generated for three fluorescent compounds: ethidium bromide; Hoechst 33342; and fluorescein, and three colored compounds: thiazol yellow G; tartrazine; and a mixture of bromphenol blue and xylene cyanol. Three different "environmentally friendly" cocktails were used: one with a linear alkylbenzene solvent; one with a diisopropylnapthalene solvent; and a third with a phenylxylylethane solvent. The data, generated from two different liquid scintillation spectrometers that use different quench indicating parameters, suggest that the quench from the fluorochromes and colored dyes with moderate amounts of quench can be corrected by chemical quench curves. The data also suggest that the quench curve of diisopropylnapthalene-based cocktails is significantly different from the other "environmentally friendly" cocktails, when examined using tSIE as the quench indicating parameter.