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@ARTICLE{Humpert:1014710,
      author       = {Humpert, Swen and Hoffmann, Chris and Neumaier, Felix and
                      Zlatopolskiy, Boris and Neumaier, Bernd},
      title        = {{V}alidation of analytical {HPLC} with post-column
                      injection as a method for rapid and precise quantification
                      of radiochemical yields},
      journal      = {Journal of chromatography / B},
      volume       = {1228},
      issn         = {1570-0232},
      address      = {New York, NY [u.a.]},
      publisher    = {Science Direct},
      reportid     = {FZJ-2023-03405},
      pages        = {123847 -},
      year         = {2023},
      abstract     = {Accurate assessment of isolated radiochemical yields (RCYs)
                      is a prerequisite for efficient and reliable optimization of
                      labeling reactions. In practice, radiochemical conversions
                      (RCCs) determined by HPLC analysis of crude reaction
                      mixtures are often used to estimate RCYs. However,
                      incomplete recovery of radioactivity from the stationary
                      phase can lead to significant inaccuracies if RCCs are
                      calculated based on the activity eluted from the column
                      (i.e. the summed integrals of all peaks). Here, we validate
                      a simple and practical method that overcomes problems
                      associated with retention of activity on the column by
                      determination of the total activity in the sample using
                      post-column injection. Post-column injections were carried
                      out using an additional injection valve, which was placed
                      between the outlet of the HPLC column and the inlet of the
                      detectors. 2-[18F]Fluoropyridine ([18F]FPy) and
                      8-cyclopentyl-3-(3-[18F]fluoropropyl)-1-propylxanthine
                      ([18F]CPFPX) were prepared with radiochemical purities of
                      $>99.8\%$ and mixed with [18F]fluoride at a ratio of 1:1 to
                      simulate reaction mixtures obtained by radiolabeling
                      reactions with an RCC of $50\%.$ The samples were analyzed
                      on three different C18 HPLC columns using neutral and acidic
                      mobile phases. RCCs determined using the summed area of all
                      peaks in the chromatograms were compared with those
                      determined using post-column injection. Additionally, RCCs
                      determined by post-column injection were corrected for
                      activity losses before, during and after radiosyntheses to
                      afford analytical RCYs, which were compared with isolated
                      RCYs. Determination of RCCs based on the summed area of all
                      peaks gave correct results under certain chromatographic
                      conditions, but led to overestimation of the actual RCCs by
                      up to $50\%$ in other cases. In contrast, determination of
                      RCCs using post-column injection provided precise results in
                      all cases, and often significantly reduced analysis time.
                      Moreover, analytical RCYs calculated from RCCs determined by
                      post-column injection showed excellent agreement with
                      isolated RCYs $(<3\%$ deviation). In conclusion, HPLC
                      analysis using post-column injection enables reliable
                      determination of RCCs independent of the chromatographic
                      conditions and, together with a simple activity balance,
                      rapid and accurate prediction of isolated RCYs.},
      cin          = {INM-5},
      ddc          = {540},
      cid          = {I:(DE-Juel1)INM-5-20090406},
      pnm          = {5253 - Neuroimaging (POF4-525)},
      pid          = {G:(DE-HGF)POF4-5253},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {37634390},
      UT           = {WOS:001070859200001},
      doi          = {10.1016/j.jchromb.2023.123847},
      url          = {https://juser.fz-juelich.de/record/1014710},
}