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Unusual Temperature-Retention Dependences Observed for Several Benzodiazepines in RP-HPLC Using Different Mobile Phase Compositions |
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| Authors: | Galaon Toma Anghel Dan-Florin David Victor Aboul-Enein Hassan Y. |
| Affiliation: | 1.Department of Analytical Chemistry, Faculty of Chemistry, University of Bucharest, Sos. Panduri, No. 90, 050663, Bucharest, Romania ;2.Laboratory of Colloids, “Ilie Murgulescu” Institute of Physical Chemistry, Romanian Academy, Spl. Independenţei, No. 202, 060021, Bucharest, Romania ;3.Pharmaceutical and Drug Industries Research Division, Pharmaceutical and Medicinal Chemistry Department, National Research Centre, Dokki, Cairo, 12311, Egypt ; |
| Abstract: | Non-linear van’t Hoff plots were observed for several benzodiazepines over the usual temperature interval used in RP-LC (10–60 °C), when acetonitrile was added in the mobile phase. Such deviation from linearity was not observed when methanol or isopropanol was added to the mobile phase. Polynomial regressions were applied to fit the experimental data when acetonitrile was used as organic additive in mobile phase. The second-order polynoms may allow finding out the maximum retention depending on temperature, which can be within or out of the normal temperature range used in RP mechanism. A thermodynamic model deriving from the partition of two or more tautomers of the same analyte was proposed to explain this deviation from linearity of van’t Hoff plots. |
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