Separation of TcO₄^- and MoO₄^2- using a PEG coated C18 SPE cartridge

Objectives A critical aspect in the feasibility of routine cyclotron production of ^99mTc via the ¹⁰⁰Mo(p,2n)^99mTc reaction is the separation of ^99mTc from the bulk ¹⁰⁰Mo target. The aim of this work was to assess if polyethylene glycol (PEG) coated on commercially available solid phase extraction (SPE) cartridges can be a viable method for the separation of pertechnetate (TcO₄^-) from molybdate (MoO₄^2-). The recovered [^99mTc]TcO₄^- purity and the recovered MoO₄^2- yield for possible recycling was evaluated.

Methods Separations were performed on an automated chemistry unit. C18 cartridges containing 3 g of resin were coated by pouring PEG3000 solution through the cartridge and then washing with deionized water (D.I. H₂O). PEG concentration in the final product was evaluated by iodine visualization TLC. Initial separation testing was performed using generator eluted [^99mTc]TcO₄^- and [⁹⁹Mo]MoO₄^2- in a loading solution containing 300 mg Mo powder dissolved in 10 mL H₂O₂ and 10 mL (NH₄)₂CO₃ (3 M). After loading, the column was washed with 5 mL (NH₄)₂CO₃ (1 M) followed by 1.5 mL D.I. H₂O. The [^99mTc]TcO₄^- was eluted using 10 mL D.I. H₂O and passed through a strong cation exchange column and an alumina column. The [^99mTc]TcO₄^- was eluted from the alumina column using 10 mL of isotonic saline.

Results Recovery of ^99mTc was 92 ± 4 % (n=4). Greater than 99.5 % of the ⁹⁹Mo was present in the load/wash fractions (n=2) thus allowing for minimal losses in terms of recycling enriched ¹⁰⁰Mo. PEG3000 concentration in the final product was lower than the limit of detection for our TLC spot test (0.1 mg/mL), pH was 6 and the product was clear and colorless

Conclusions We developed a practical and easily accessible system for separation of ^99mTc-pertechnetate, with good recovery yields for [^99mTc]TcO₄^- and promising features for molybdenum recovery. The final product passed appropriate QC tests.

Research Support This work was supported by research grants from NSERC/CIHR and Natural Resources Canada.