Versatile semiautomated sample processor and gamma counter to increase radioimmunoassay efficiency.

We describe a semiautomated batch-assay system designed to increase the speed and ease of performing radioimmunoassays while maintaining good accuracy and precision. The main components are a programmable pipetting unit (sample processor) and a gamma counter capable of simultaneously counting radioactivity in 12 samples. The processor uses prearranged sets of as many as 24 disposable pipette tips, which eliminates carryover between samples, and features a horizontal shaker and magnetic stirrer; 50 different assay protocols can be selected. Batches of tubes are easily transferred from the sample processor to the incubator and centrifuge. The gamma counter is controlled by a microprocessor, which is also used for data processing. Because the system is based on discrete rather than continuous-flow analysis and because of the ease with which consecutive samples can be processed, more than one operation and several different assays can be accommodated simultaneously, which saves time considerably.