title: Studies of the mechanism of the in-loop synthesis of radiopharmaceuticals.
abstract: A series of experiments were performed to better understand the mechanism of the In-loop [11C]CH3I-methylation. The timing of [11C]CH3I delivery is critical for the high yield of radiolabeling since in-loop radioactivity trapping is reversible. Trapped radioactivity escapes faster from a Tefzel loop compared to a PEEK- or stainless steel loop. Up to 50% of delivered radioactivity may be concentrated at the loop origin (representing 8.1% of the total loop volume). A five-fold reduction of the reaction solvent volume and/or precursor amount may lead to a decrease of the product radiochemical yield either by lowering the in-loop radioactivity trapping or by diminishing conversion of [11C]CH3I into the product.
authors.affiliation: TRIUMF, PET Group, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada. studenov@triumf.ca
authors.forename: Andrei R
authors.initials: AR
authors.lastname: Studenov
authors.forename: Salma
authors.initials: S
authors.lastname: Jivan
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Adam
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Ruth
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Buckley
mesh_terms: D002250:Carbon Radioisotopes / Q000032:analysis* / Q000737:chemistry*; D005283:Fentanyl / Q000031:analogs & derivatives* / Q000032:analysis / Q000138:chemical synthesis; D005740:Gases / Q000737:chemistry; D006847:Hydrocarbons, Iodinated / Q000032:analysis* / Q000138:chemical synthesis*; D007553:Isotope Labeling / Q000379:methods*; D008745:Methylation; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000032:analysis / Q000138:chemical synthesis
chemical_list: D002250:Carbon Radioisotopes; D005740:Gases; D006847:Hydrocarbons, Iodinated; D019275:Radiopharmaceuticals; C014055:methyl iodide; C017114:carfentanil; D005283:Fentanyl