Direct counting of tritium by dissolving Microelisa wells in scintillation fluid

Radioassays with low-energy beta-emitting nuclides (e.g., 3H, 14C, 35S) in 96-well plastic plates are tedious and frequently inaccurate because of the necessity of quantitatively removing and transferring the contents of each well to scintillation fluid. We therefore investigated the possibility of counting these nuclides by directly placing the entire break-apart well (Microelisa) along with the sample into one of four scintillation counting fluids: toluene-PPO-POPOP with or without Protosol, ACSR, and EcoLite. Although some of these scintillation fluids fully dissolved the plastic wells and other did not, we found that the presence of the wells did not appreciably interfere with the efficiency of tritium counting. This technique saves considerable time and reduces possible errors in liquid scintillation counting of samples from plastic microtitration plates.