A combined loop-SPE method for the automated preparation of [11C]doxepin

R. Iwata, C. Pascali, A. Bogni, K. Yanai, M. Kato, T. Ido, K. Ishiwata

Research output: Contribution to journalArticlepeer-review


A simple and versatile loop-solid phase extraction (SPE) method was developed for the automated preparation of [11C]doxepin, a histamine H1 receptor antagonist, from [11C]methyl triflate ([11C]MeOTf). This labeling agent was passed through a Teflon or Tefzel loop coated internally with a film of the precursor solution. The reaction products were then flushed from the loop to a short SPE column, where they were concentrated and then injected onto a semi-preparative HPLC column simply by switching an injection valve. By applying this combined loop-SPE technique the whole procedure turned out to be easily automated. The formation of [11C]methylated doxepin ([11C]methyldoxepin) was observed and the ratio of doxepin to methyldoxepin was found to be clearly correlated with the mass ratio of nordoxepin to MeOTf. This observation highlights the importance of [11C]MeOTf specific activity in the [11C]methylation of secondary amines. Using this method, [11C]Doxepin was prepared in over 40% radiochemical yield from high specific activity [11C]MeOTf.

Original languageEnglish
Pages (from-to)271-280
Number of pages10
JournalJournal of Labelled Compounds and Radiopharmaceuticals
Issue number4
Publication statusPublished - May 30 2002


  • Automated preparation
  • Carbon-11
  • Doxepin
  • Loop-SPE method
  • Methyl triflate

ASJC Scopus subject areas

  • Analytical Chemistry
  • Drug Discovery
  • Organic Chemistry
  • Clinical Biochemistry
  • Molecular Medicine
  • Pharmacology


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