Add time:07/29/2019         Source:sciencedirect.com

99mTc-exametazime (99mTc-d,l-HMPAO, 99mTc-d,l-hexamethylpropyleneamine oxime) is a neutral rather unstable complex of short-lived 99mTc (t1/2=6 h) with the d,l-isomer (mixture of d,d- and l,l-isomers) of a bis-amine bis-oxime tetraligand. It is widely used for measurement of regional cerebral perfusion in nuclear medicine. The meso-isomer (d,l-form) should not be present in a preparation as it is not retained in brain and thus does not provide clinically useful information. Meso-HMPAO is removed from the ligand during the synthesis procedure by repeated recrystallization, but can still be present as impurity in d,l-isomer. Due to the lack of a suitable chromatographic method for analysis of the isomeric purity of 99mTc-exametazime preparations, United States Pharmacopoeia 25 (USP 25) prescribes a biological test in rats for quality control purpose. In this study, we developed a suitable high-performance liquid chromatography (HPLC) method which allows to demonstrate the relative amounts of d,l- and meso-isomer in 99mTc-exametazime and so obviates the need for a biodistribution test in animals as part of the quality control. Due to the low concentrations in which 99mTc-d,l-HMPAO is obtained (typically 2–6 ng/ml), confirmation of the identity of 99mTc-d,l-HMPAO in the monograph of the European Pharmacopoeia is now performed only indirectly by TLC and assessment of its retention time on RP-HPLC. To investigate the potential of radio-LC–MS for assessment of the identity of 99mTc-exametazime, 99mTc-d,l-HMPAO and 99mTc-meso-HMPAO prepared using a Tc-rich eluate were analyzed using a radio-LC–MS system equipped with a time-of-flight mass spectrometer with electrospray ionization. The main peak in the radiometric channel coincided with the molecular ion mass of 99mTc-d,l-HMPAO in the mass spectrometer channel and the measured accurate mass differed only by 0.26 ppm from the theoretical mass. The identity of 99mTc-meso-HMPAO was also confirmed. Thus, radio-LC–MS allowed to obtain strong evidence for the structure of 99mTc-d,l-HMPAO and 99mTc-meso-HMPAO at nanomolar concentration. It is concluded that radio-LC–MS can become a sensitive aid in quality control of “no carrier added” radiopharmaceutical preparations.

We also recommend Trading Suppliers and Manufacturers of Technetium Tc 99m Exametazime (cas 100504-35-6). Pls Click Website Link as below: cas 100504-35-6 suppliers