Low-Water [18F] Radiolabelling for Higher Yield and Purity
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Solution Overview
Problem
Existing methods for preparing [18F]fluoride radiolabelled compounds suffer from high radiochemical impurities and low yields due to insufficient control over water content and origin during the radiolabelling process, particularly at high radioactivity levels.
Innovation Solution
An improved method involving initial drying and azeotropic distillation with acetonitrile to reduce water content to less than 500 ppm from the [18F]fluoride solution and precursor compound to less than 2000 ppm, followed by a fluoride activation drying step with multiple acetonitrile cycles to minimize free radical formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional drying methods are used to remove water from [18F]fluoride solution, then the drying process is simple, but the water content after drying is insufficiently controlled (greater than 500 ppm), leading to high radiochemical impurities and low yields
Solution Approach 1:
The drying process is divided into multiple sequential steps: initial drying to remove bulk water, followed by multiple azeotropic distillation cycles with acetonitrile to remove residual water. This segmentation allows precise control of water content at each stage, achieving the target of less than 500 ppm while maintaining process manageability through systematic progression.
Solution Approach 2:
The method utilizes changes in physical parameters during drying - specifically temperature and pressure conditions during evaporation and azeotropic distillation. By controlling these parameters, the process achieves selective removal of water while preserving [18F]fluoride integrity, achieving precise water content control without excessive complexity.
2Productivity
If higher starting radioactivity levels are used to increase productivity, then more patient doses can be produced, but free radical formation increases causing higher radiochemical impurities and lower yields
Solution Approach 1:
The method performs preliminary drying and azeotropic distillation cycles before the radiolabelling reaction to remove water that would otherwise generate free radicals during irradiation. This preliminary action prevents free radical formation during the high-radioactivity labelling step, enabling higher starting activities (up to 500 GBq) to be used without excessive impurity formation, thus increasing productivity.
3Reliability
If water content is not严格控制 during labelling, then the process is simpler and faster, but radiochemical impurities increase and yield decreases
Solution Approach 1:
The drying process continues through multiple azeotropic distillation cycles until the water content target is achieved, ensuring continuous removal of water without interruption. This continuous action ensures reliable radiochemical purity (greater than 95%) while the automated nature of the process minimizes time loss compared to manual monitoring and adjustment methods.
Data Source
AI summary
The invention relates to a method of preparing an [18F]radio-labelled compound, wherein the water content is controlled. Controlling the water content and the origin of the water within the reaction process has a significant effect on both the yield and the purity of the product of the radiolabelling process.