title: Dual-isotope separation technique for radioassay. Precision of calculated results affected by degree of separation.
abstract: The dual-isotope separation technique for radioassay is reviewed. An expression is derived describing the effect of counting errors on the precision of the calculated bound count rate in the dual-isotope technique. This mathematic model is tested in experiments using sodium iothalamate (I-125) as a marker in the Phadebas radiosorbent assay of cobalamin (Co-57). The coefficient of variation of results calculated on the basis of the dual-isotope technique is shown to be dependent on the amount of supernatant removed. The conclusion is that relatively large amounts of the supernatant must be removed before counting if the dual-isotope technique is to give acceptable results. The experimental model is proposed as a simple test of the suitability of a projected dual-isotope system.
mesh_terms: D000704:Analysis of Variance; D003037:Cobalt Radioisotopes; D007457:Iodine Radioisotopes; D007483:Iothalamic Acid; D008433:Mathematics; D011852:Radioallergosorbent Test / Q000379:methods; D011863:Radioimmunoassay / Q000379:methods*; D011868:Radioisotopes / Q000302:isolation & purification; D011933:Reagent Kits, Diagnostic; D014805:Vitamin B 12 / Q000032:analysis
chemical_list: D003037:Cobalt Radioisotopes; D007457:Iodine Radioisotopes; D011868:Radioisotopes; D011933:Reagent Kits, Diagnostic; D007483:Iothalamic Acid; D014805:Vitamin B 12