A rapid and systematic approach for the optimization of radio thin-layer chromatography resolution

Travis S Laferriere-Holloway; Alejandra Rios; Yingqing Lu; Chelsea C Okoro; R Michael van Dam

doi:10.1016/j.chroma.2022.463656

A rapid and systematic approach for the optimization of radio thin-layer chromatography resolution

J Chromatogr A. 2023 Jan 4:1687:463656. doi: 10.1016/j.chroma.2022.463656. Epub 2022 Nov 22.

Authors

Travis S Laferriere-Holloway¹, Alejandra Rios², Yingqing Lu², Chelsea C Okoro³, R Michael van Dam⁴

Affiliations

¹ Department of Molecular & Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, CA, USA; Crump Institute for Molecular Imaging, UCLA, Los Angeles, CA, USA. Electronic address: tholloway@mednet.ucla.edu.
² Physics and Biology in Medicine Interdepartmental Graduate Program, UCLA, Los Angeles, CA, USA; Crump Institute for Molecular Imaging, UCLA, Los Angeles, CA, USA.
³ Institute for Society and Genetics, UCLA, Los Angeles, CA, USA; Crump Institute for Molecular Imaging, UCLA, Los Angeles, CA, USA.
⁴ Department of Molecular & Medical Pharmacology, David Geffen School of Medicine, University of California Los Angeles (UCLA), Los Angeles, CA, USA; Physics and Biology in Medicine Interdepartmental Graduate Program, UCLA, Los Angeles, CA, USA; Crump Institute for Molecular Imaging, UCLA, Los Angeles, CA, USA. Electronic address: mvandam@mednet.ucla.edu.

Abstract

Radiopharmaceutical analysis is limited by conventional methods. Radio-HPLC may be inaccurate for some compounds (e.g., ¹⁸F-radiopharmaceuticals) due to radionuclide sequester. Radio-TLC is simpler, faster, and detects all species but has limited resolution. Imaging-based readout of TLC plates (e.g., using Cerenkov luminescence imaging) can improve readout resolution, but the underlying chromatographic separation efficiency may be insufficient to resolve chemically similar species such as product and precursor-derived impurities. This study applies a systematic mobile phase optimization method, PRISMA, to improve radio-TLC resolution. The PRISMA method optimizes the mobile phase by selecting the correct solvent, optimizing solvent polarity, and optimizing composition. Without prior knowledge of impurities and by simply observing the separation resolution between a radiopharmaceutical and its nearest radioactive or non-radioactive impurities (observed via UV imaging) for different mobile phases, the PRISMA method enabled the development of high-resolution separation conditions for a wide range of ¹⁸F-radiopharmaceuticals ( [¹⁸F]PBR-06, [¹⁸F]FEPPA, [¹⁸F]Fallypride, [¹⁸F]FPEB, and [¹⁸F]FDOPA). Each optimization required a single batch of crude radiopharmaceutical and a few hours. Interestingly, the optimized TLC method provided greater accuracy (compared to other published TLC methods) in determining the product abundance of one radiopharmaceutical studied in more depth ( [¹⁸F]Fallypride) and was capable of resolving a comparable number of species as isocratic radio-HPLC. We used the PRISMA-optimized mobile phase for [¹⁸F]FPEB in combination with multi-lane radio-TLC techniques to evaluate reaction performance during high-throughput synthesis optimization of [¹⁸F]FPEB. The PRISMA methodology, in combination with high-resolution radio-TLC readout, enables a rapid and systematic approach to achieving high-resolution and accurate analysis of radiopharmaceuticals without the need for radio-HPLC.

Keywords: PRISMA optimization; Radiochemistry; high-resolution; radio-TLC; radiopharmaceuticals.

MeSH terms

Benzamides*
Chromatography, High Pressure Liquid
Chromatography, Thin Layer / methods
Radiopharmaceuticals*
Solvents

Substances

Radiopharmaceuticals
fallypride
Benzamides
Solvents

Abstract

MeSH terms

Substances

Grants and funding