Synthesis and radiolabeling of technetium radiopharmaceuticals based on N-substituted iminodiacetic acid: Effect of radio-labeling conditions on radiochemical purity
✍ Scribed by Anna T. Fields; David W. Porter; Patrick S. Callery; Elizabeth B. Harvey; Michael D. Loberg
- Publisher
- John Wiley and Sons
- Year
- 1978
- Tongue
- French
- Weight
- 432 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0022-2135
No coin nor oath required. For personal study only.
✦ Synopsis
Prerequisite t o the development of technetium-99m
containing drug and biochemical analogs is the ability t o synthesiEe radiochemically pure technetium chelates from mixtures of an appropriate chelating agent, pertechnetate, and various reducing agents. T h i s paper reports the synthesis of a aeries of N-substituted iminodiacetates (IDA) in which the pKa of the imino nitrogen was varied from 5.0 t o 8.7.
T h e chelating agent8 were labeled with Tc-99m using the stannous reduction method at aqueous pH's of 4.0, 5.5 and 8 . 0 and in absolute methanol.
T h e radiochemical purity of each chelate was examined by high preaaure liquid chromatography, pbper electrophoresis, paper chromatography, and tissue distribution studies. Aqueous radiolabeling conditions resulted in pure technetium chelates only when the pKa of the imino nitrogen w a s approximately 6. Methanolic labeling conditions resulted in pure radiochemicals for all N-substituted iminodiacetic acids provided the imino nitrogen had a pKa of greater than 6. Under non-aqueous conditions, however, t h e radiochemical purity deteriorated with time for all compounds in which the pKa of the imino nitrogen was greater than 7. These results indicate that only those IDA derivative8 in which the in vivo nitrogen has a pKa of approximately 6 show a high degree of radiochemical purity when radiolabeled using stannous ion as t h e reducing agent.