New sensitive method for HEPES quantification in ⁶⁸Ga-radiopharmaceuticals

Area of Science:

• Nuclear Medicine
• Radiopharmaceutical Chemistry
• Analytical Chemistry

Background:

• GMP-certified ⁶⁸Ga generators have increased ⁶⁸Ga-radiopharmaceutical use.
• 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (HEPES) buffer improves radiosynthesis but is an impurity.
• European Pharmacopoeia (Ph Eur) limits HEPES to 200 μg/V_Injected for radiopharmaceuticals like edotreotide.

Purpose of the Study:

• To evaluate the sensitivity of the Ph Eur thin-layer chromatography (TLC) method for HEPES quantification.
• To develop and validate a new high-performance liquid chromatography (HPLC) method for HEPES quantification in ⁶⁸Ga-radiopharmaceuticals.
• To compare the new HPLC method with the Ph Eur TLC method and assess HEPES levels in various ⁶⁸Ga-radiopharmaceuticals from different institutes.

Main Methods:

• Tested the Ph Eur TLC method for HEPES detection in ⁶⁸Ga-radiopharmaceuticals.
• Developed and validated a modified TLC method and a new HPLC method for HEPES quantification.
• Analyzed ⁶⁸Ga-radiopharmaceutical samples from multiple institutions using the developed methods.

Main Results:

• The Ph Eur TLC method failed to detect HEPES within 4 minutes of iodine incubation.
• The modified TLC method required 2 hours for visible spots, only at concentrations >1 mg/mL.
• The HPLC method achieved a limit of quantification (LOQ) of 3 μg/mL and a limit of detection (LOD) of 1 μg/mL, detecting excessive HEPES in [⁶⁸Ga]Ga-NODAGA-Exendin samples.

Conclusions:

• The Ph Eur and modified TLC methods are insufficiently sensitive for quality control (QC) of HEPES in ⁶⁸Ga-radiopharmaceuticals.
• The new HPLC method is sensitive, quantitative, reproducible, and suitable for QC release.
• This HPLC method identified ⁶⁸Ga-radiopharmaceutical batches exceeding the pharmacopoeial HEPES limit, enabling dose adjustment for patient safety.