Preparation of whole blood for liquid scintillation counting

Liquid scintillation counting of 3H-labeled whole-blood samples is severely impaired owing to quenching by blood pigments. In this study, dry oxidation and chemical solubilization followed by decolorization were the two general methods used to eliminate color quenching. Three blood volumes were examined: 0.25, 0.50, and 1.0 mL. Dry oxidation yielded complete recoveries of 3H label with counting efficiencies greater than 30% for up to 1.0 mL of blood. Although blood volumes larger than 0.25 mL can be used with chemical solubilization and decolorization, treatment of 0.25 mL of blood gave the highest counting efficiencies, with count rates comparable to those for 1.0-mL samples.