Counting Aqueous Samples with the TopCount Microplate Scintillation Counter

The TopCountTM Microplate Scintillation Counter quantitates radioisotopes by liquid scintillation counting in standard microplate formats. Assays that previously had to be transferred from microplates to vials or to non-standard formats for counting can now be quantitated directly in microplates. TopCount can count up to 12 samples simultaneously with performance comparable to that of discrete sample liquid scintillation counters. Effects of sample quench can be corrected with quench indicating parameters based on the sample spectrum (tSIS) or, when using the 4 X 6 format, external standard spectrum (tSIE). With multiple detectors and the microplate format, TopCount offers greater throughput, decreased cocktail consumption, more efficient sample handling, and more secure sample identification. Samples from a cytotoxicity assay and an enzyme inhibition assay were counted on TopCount, and the results were compared to those obtained with conventional liquid scintillation and gamma counting.