Eichrom’s SCX (strong cation exchange) silica contains sulfonic acid groups chemically bonded to irregular silica. The SCX silica is thoroughly purified to remove metal ion contamination to improve radiolabeling of purified radionuclides in nuclear medicine applications.
Specifications
substrate: irregular silica
particle size: 35-60 µm
porosity: 60Å,
surface area: 450 m2 /g
pH stability: 2-10
Dry weight distribution ratios (Dw) for selected metal ions on the SCX-silica vs HCl are provided in figures 1-6.
One application of the SCX-silica is the purification of 68Ga. The 68Ga is produced by elution from a generator column containing its parent 68Ge with 0.1M HCl. The 68Ga is trapped on the SCX-silica from the 0.1M HCl, while 68Ge and many stable metals pass through. The 68Ga is then recovered using a small volume of 5M NaCl – 0.1M HCl.[1] Elution curves for 68Ga (Figure 7) and many other stable metals (Figures 8 – 11) on SCX-silica are presented below.
Figure 7. Elution of 68Ga on QML (0.25 mL) cartridge of SCX silica.
Figure 8. Elution of alkali and alkaline earth metals and Pb on a 2 mL cartridge of SCX silica.
Figure 9. Elution of rare earth metal ions on 2 mL cartridge of SCX silica.
Figure 10. Elution of U and Th decay element metal ions on 2 mL cartridge of SCX silica.
Figure 11. Elution of selected transition metal ions on a 2 mL cartridge of SCX silica.
Many radionuclides used in nuclear medicine applications are received in mineral acid solutions, such as dilute HCl. Prior to radiolabeling of the metal ions to biolocalization agents through chelation, it is often necessary to convert the matrix of the radionuclides into a biocompatible buffer such as sodium acetate or ammonium acetate with a pH of 4.5 – 6.5. Another application of SCX-silica is the concentration of radionuclides from dilute acid, such as 0.01 – 0.10M HCl, and then elution from SCX-silica with a buffer solution.[2,3] Examples of this application for 225Ac, 203Pb, 90Y, 227Th, and 44Sc are presented in figures 12-16.
Figure 12. Elution of 225Ac on a QML (0.25 mL) cartridge of SCX silica.
Figure 13. Elution of 203Pb on a QML (0.25 mL) cartridge of SCX silica.
Figure 14. Elution of 90Y on a QML (0.25 mL) cartridge of SCX silica.
Figure 15. Elution of 227Th on a QML (0.25 mL) cartridge of SCX silica.
Figure 16. Elution of 44Sc on a QML (0.25 mL) cartridge of SCX silica.
References:
[1] Schultz, M. K.; Mueller, D.; Baum, R. P.; Leonard Watkins, G.; Breeman, W. A. P. A New Automated NaCl Based Robust Method for Routine Production of Gallium-68 Labeled Peptides. Applied Radiation and Isotopes 2013, 76, 46–54. https://doi.org/10.1016/j.apradiso.2012.08.011.
[2] M.A. Eddy, E. Rush, D. R. McAlister, “Recovery of Select f-elements, Y and Sc from chromatographic resins in an acetate buffer,” Solv. Extr. Ion Exch., submitted (2025).
[3] van der Meulen, N. P.; Bunka, M.; Domnanich, K. A.; Müller, C.; Haller, S.; Vermeulen, C.; Türler, A.; Schibli, R. Cyclotron Production of 44Sc: From Bench to Bedside. Nucl Med Biol 2015, 42 (9), 745–751. https://doi.org/10.1016/j.nucmedbio.2015.05.005.