The fractionation of US mercaptoacetyltriglycene (MAG3) cold kits provides an economical way of preparing 99Tcm-MAG3. However, our nuclear pharmacy noted that fractionated 99Tcm-MAG3 kits sometimes failed radiochemical purity (RCP) testing (i.e. RCP < 90%) when a 99Tcm eluate of older age was used. The purpose of this study was to evaluate the effects of eluate age on the radiochemical purity of fractionated 99Tcm-MAG3 kits. Each of four US MAG3 cold kits was initially diluted with 10 ml N2-purged 0.9% NaCl solution and subdivided into 10 aliquots of 1 ml MAG3 solution and overlayered with N2. The 40 fractionated MAG3 vials were immediately frozen at -20 degrees C for storage. Fractionated MAG3 kits were reconstituted with 1 ml of approximately 111 GBq 99Tcm eluate from a long-ingrowth generator (i.e. > or = 72 h) every hour during the 6 h post-elution period. The RCP of each 99Tcm-MAG3 preparation was determined using the recommended Sep-Pak C18 column chromatography 1, 2, 3, 4, 5 and 6 h post-reconstitution. All fractionated MAG3 kits prepared with 99Tcm eluates 4 h post-elution or less maintained an average RCP value of 96.3 +/- 2.5% (n = 144) throughout the 6 h evaluation period following preparation. However, 99Tcm eluates 5 and 6 h post-elution resulted in kit failure rates of 16.7% (1/6) with RCP = 89.3%, and 50% (3/6) with RCP = 88.2, 83.9 and 87.1%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)