Two different 96-well filter plate formats were investigated, a UniFilterTM GF/B filtration plate3 and a FlexiFilter 4 containing a nylon membrane. FlexiFilter is a microplate format tray with an associated collimator designed to hold a membrane or filter of the users choice. The 96-well UniFilter and FlexiFilter plates were counted wet. The same crosstalk pattern was used as described for OptiPlates.
Counting Counting performance in 0.4 and 1.5 mL microcentrifuge tubes containing varying amounts of water was assessed. Constant activity of 147,215 DPM was pipetted into a series of microfuge tubes. The 0.4 mL microcentrifuge tubes contained the following total volumes of water: 5, 10, 50, 100, 200, and 400 μL in duplicate. The 1.5 mL tubes contained 10, 50, 100, 500, 1000, and 1500 μL of water. Counting efficiency and backgrounds were determined on the TopCount by counting with the appropriate carrier microplates.
The effect of different liquid sample volumes in 96- and 24-well OptiPlates was investigated. Triplicate wells were prepared with the following total volumes of water: 0 (dry), 10, 25, 50, 100, and 300 μL in a 96-well OptiPlate. Triplicate wells were prepared in a 24-well OptiPlate with the following water volumes: 0.5 mL, 1.0 mL, and 1.5 mL. All wells were counted for five minutes.
Linearity Count rate linearity was investigated in a 96-well OptiPlate by spiking wells in triplicate with dilutions of 32P ranging from 1.3 million DPM to 40 DPM. The total volume of water per well was 150 μL. Each well was counted for five minut