Color quenching in "environmentally friendly" cocktails

Area of Science:

• Radiochemistry
• Environmental Science
• Analytical Chemistry

Background:

• Fluorescent and colored compounds in molecular biology labs can cause color quench in wipe test samples.
• The effectiveness of conventional chemical quench curves in correcting color quench from these compounds in "environmentally friendly" cocktails is not well-documented.

Purpose of the Study:

• To evaluate the ability of chemical quench curves to correct for color quench induced by fluorescent and colored compounds in "environmentally friendly" liquid scintillation cocktails.
• To compare the quench characteristics of different "environmentally friendly" cocktails using various quench indicating parameters.

Main Methods:

• Generated series of colored samples spiked with tritium (3H) or carbon-14 (14C).
• Tested three fluorescent compounds (ethidium bromide, Hoechst 33342, fluorescein) and three colored compounds (thiazol yellow G, tartrazine, bromphenol blue/xylene cyanol mixture).
• Utilized three "environmentally friendly" cocktails with different solvents: linear alkylbenzene, diisopropylnapthalene, and phenylxylylethane.
• Analyzed data from two liquid scintillation spectrometers using different quench indicating parameters, including the Transformed Spectral Index of the Eluate (tSIE).

Main Results:

• Chemical quench curves effectively corrected for color quench from fluorochromes and colored dyes at moderate quench levels.
• The diisopropylnapthalene-based cocktail exhibited a significantly different quench curve compared to the other cocktails when analyzed using tSIE.
• Quench correction was feasible across different "environmentally friendly" cocktails, though solvent choice impacts quench curve characteristics.

Conclusions:

• Conventional chemical quench curves are suitable for correcting color quench in wipe test samples from molecular biology labs, even in the presence of fluorescent and colored compounds.
• "Environmentally friendly" cocktails, particularly those based on diisopropylnapthalene, require careful consideration of quench indicating parameters like tSIE for accurate quantification.
• The choice of solvent in "environmentally friendly" scintillation cocktails influences quench characteristics and necessitates method-specific validation.