Speciation of no-carrier-added 68Ga prior to its labeling for PET imaging
The present article describes the probable speciation of68Ga radionuclide just before labeling to DOTA peptides for PET imaging. The68Ga eluted from an anion exchange column after its purification was analyzed for its elemental composition and pH at several stages. Neutron activation analysis of the eluted fractions yields the concentrations of Na and Cl, pH measurements indicate the concentration of free H+ions in the medium and specific activity calculations indicate the concentration of68Ga in the solution. Using all these information we get the idea of speciation of no carrier added Ga in the eluted fractions from CHEAQS programme. The estimations indicate that Ga is mostly present as GaCl2+in the total MiliQ eluate. However, just before labeling of DOTA the pH of the Ga-containing eluate is adjusted to ~3.5 using HEPES buffer and at that condition Ga remains as Ga3+species which is responsible for a successful and efficient labeling. The MilliQ eluate collected before actual labeling was estimated for trace elements using inductively coupled plasma atomic emission spectrometry was found to contain a few ppb of Al, Co, Pd and Pt that did not interfere in the actual labeling. A clear idea about the prerequisite of68Ga species before labeling to a peptide might be of special interest for its judicious application as a radiopharmaceutical.