Introduction: ^99mTc-sestamibi is a lipophilic cation which, when injected intravenously into a patient, distributes in the myocardium proportionally to the myocardial blood flow. The drug is a coordination complex of the radioisotope technetium-^99mwith the ligand methoxyisobutylisonitrile (MIBI). As with all other preparations of 99mTc-labelled radiopharmaceuticals, 99mTcO4, reduced-hydrolysed ^99mTc (^99mTcO2) or any other 99mTc complexes species may be present in the preparation of ^99mTc-MIBI.

Objetive: The aim of this work was to evaluate and validate the radiochemical purity of a commercial lyophilized “kit” of MIBI labeled with ^99mTc by three different chromatographic methods, and indicate the optimal method for quality control routine in nuclear medicine service in accordance to the rules of ANVISA (RDC38), before the dose administration in patient

Material and methods: ^99mTc-MIBI was prepared from a lyophilized kit following manufacturer´s instructions, by adding no more than 11,100MBq / 3-5mL freshly eluted 99mTc-pertechnetate from a ⁹⁹Mo/^99mTc generator (IPEN-Tec), heated hermetically in boiling water for 10 minutes and cooled to room temperature. The 99mTc must be recently eluted (<2hours) and the content of ⁹⁹Mo determined before labeling process, as well the pH, the aluminum ion contamination and the radiochemical assay by Whatman3MM chromatography paper in 85% methanol. After cooling, the final product was submitted to radiochemical purity tests. Three different chromatographic systems tests were performed in radiochemical quality control of ^99mTc-MIBI: solvent extraction (chloroform: 0.9%NaCl), paper chromatographic (Whatman3MM in 20% saline and 85% methanol) and solid phase extraction (Sep-Pak C18) at three different times (30; 120 and 240 minutes), after the addition of 99mTc.

Results: The values ??obtained by chromatography paper were (98.70 ± 0.98)%, solid phase extraction (98.85 ± 0.72)% and solvent extraction (98.75 ± 0.45 )%, at 30 minutes after labeling. The solid phase extraction values were: (98.60 ± 0.32)% and (98.55 ± 0.73)% at 120 and 240 minutes, respectively. In more than 52 samples, by solid phase extraction, the value was (99.10 ± 0.84)% at 30 minutes after labeling.

Conclusion: It was demonstrated the efficiency of these chromatographic techniques in the quality control test of ^99mTc-MIBI, defining the faster solid phase extraction (Sep-Pak C18) as the ideal assay in the routine process at nuclear medicine service. Acute exposures to chloroform have been reported to induce depression of the central nervous system and to cause liver and renal toxicity, considering this method no appropriate in routine. The results obtained in this study: Rf range, labeling efficiency and time required to complete the experiments are consistent to adapted in the hospital radiopharmacy.