Discrete modular system for automation of radioimmunoassay of serum choriomammotropin.

We describe a discrete automated radioimmunoassay system for determining choriomammotropin (placental lactogen) in human serum. With the present system it can be measured in as many as 37 unknown sera (50 muL) and three quality-control sera, in duplicate, within 1.5 h. The time required for sample preparation, incubation (15 min), and separation of free and bound radioactivities (a 150 mL/L polyethylene glycol solution is superior to a twofold volume of absolute ethanol) is less than 45 min. The remaining time required is for counting and data processing. Intra-assay precision is 4.6% (CV). The modular approach endows the instrumentation with much flexibility, and consequently is suitable for automation of a wide range of assay protocols.