{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,5]],"date-time":"2026-04-05T12:11:48Z","timestamp":1775391108572,"version":"3.50.1"},"reference-count":20,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2013,12,19]],"date-time":"2013-12-19T00:00:00Z","timestamp":1387411200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Enantioseparation is largely based on the formation of transitional complexes, the solvation species, the stationary phase configurations or the diastereomeric complexes formed by analytes and the chiral stationary phase. Temperature and the chemical nature and composition of the eluent play significant roles during that process. In this study; unique temperature-induced behaviors were observed during the enantioseparation of Koga tetraamines, also known as Koga bases, on polysaccharide chiral stationary phases, in which van\u2019t Hoff plots were acquired over a temperature range of 10 \u00b0C to 40 \u00b0C with 5 \u00b0C increments. Koga bases were eluted by a mixture of methanol and 2-propanol with 0.03% triethylamine as a modifier. The van\u2019t Hoff plots are linear in the case of eluent containing equal volumes of methanol and 2-propanol. Increasing 2-propanol concentration from 50% to 85% in volume led to non-linear van\u2019t Hoff plots over the entire temperature range studied. Examination of the individual non-linear plots revealed two linear regions of  10 \u00b0C\u201320 \u00b0C and 20 \u00b0C\u201340 \u00b0C. Transition from one linear region to the other at 20 \u00b0C indicates alterations of chiral stationary phase conformation and\/or enantioseparation mechanism as a result of temperature changes.<\/jats:p>","DOI":"10.3390\/molecules19010009","type":"journal-article","created":{"date-parts":[[2013,12,19]],"date-time":"2013-12-19T11:26:58Z","timestamp":1387452418000},"page":"9-21","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Influence of Temperature on the Enantioselectivity of Koga Tetraamines on Amylose Chiral Stationary Phases"],"prefix":"10.3390","volume":"19","author":[{"given":"Hong-Xun","family":"Guo","sequence":"first","affiliation":[{"name":"Analytical Research and Development, Amgen, Inc., One Amgen Center Drive, Thousand Oaks,  CA 91320, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Steven","family":"Wu","sequence":"additional","affiliation":[{"name":"Analytical Research and Development, Amgen, Inc., One Amgen Center Drive, Thousand Oaks,  CA 91320, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jingshun","family":"Sun","sequence":"additional","affiliation":[{"name":"Analytical Research and Development, Amgen, Inc., One Amgen Center Drive, Thousand Oaks,  CA 91320, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2013,12,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"5901","DOI":"10.1016\/j.chroma.2010.07.043","article-title":"Thermodynamic and kinetic study of chiral separations of coumarin-based anticoagulants on derivatized amylose stationary phase","volume":"1217","author":"Gebreyohannes","year":"2010","journal-title":"J. Chromatogr. A"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"814","DOI":"10.1016\/j.chroma.2009.10.022","article-title":"Chiral recognition by enantioselective liquid chromatography: Mechanisms and modern chiral stationary phases","volume":"1217","year":"2010","journal-title":"J. Chromatogr. A"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1021\/op0602371","article-title":"Dynamic biphasic counter ion exchange in a configurationally stable Aziridinium ion: Efficient synthesis and isolation of a koga C2-symmetric tetraamine base","volume":"11","author":"Frizzle","year":"2007","journal-title":"Org. Proc. R. D."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"50","DOI":"10.1002\/chir.20704","article-title":"Effects of solvent on chiral and enantiomeric separation of Koga bases using derivatized amylose chiral stationary phase","volume":"22","author":"Guo","year":"2009","journal-title":"Chirality"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"4190","DOI":"10.1021\/ac0103672","article-title":"Solid-state NMR characterization of amylose tris-(3, 5-dimethylphenylcarbamate) chiral stationary-phase structure as a function of mobile-phase composition","volume":"73","author":"Wenslow","year":"2001","journal-title":"Anal. Chem."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"5877","DOI":"10.1021\/ac034714e","article-title":"Characterization of a thermally induced irreversible conformational transition of amylose tris-(3, 5-dimethylphenylcarbamate) chiral stationary phase in enantioseparation of dihydropyrimidinone acid by quasi-equilibrated liquid chromatography and solid-state NMR","volume":"75","author":"Wang","year":"2003","journal-title":"Anal. Chem."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"14114","DOI":"10.1021\/jp061892d","article-title":"Direct probing of sorbent\u2212solvent interactions for amylose tris(3,5-dimethylphenylcarbamate) using infrared spectroscopy, X-ray diffraction, solid-state NMR, and dft modeling","volume":"B110","author":"Kasat","year":"2006","journal-title":"J. Phys. Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"192","DOI":"10.1002\/anie.198901921","article-title":"Temperature dependent inversion of elution sequence in the resolution of \u03b1-amino acid enantiomers on chiral diamide selectors","volume":"28","author":"Watabe","year":"1989","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/S0021-9673(01)96748-2","article-title":"Thermodynamic properties of enantiomers of underivatized diols versus the cyclic carbonates in gas chromatography on Chirasil-Val","volume":"481","author":"Koppenhoefer","year":"1989","journal-title":"J. Chromatogr. A"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"194","DOI":"10.1002\/anie.198901941","article-title":"Evidence for temperature dependent reversal of the enantiomselectivity in complexation gas chromatography on chiral phases","volume":"28","author":"Schurig","year":"1989","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"270","DOI":"10.1016\/j.chroma.2012.10.006","article-title":"A practical method for the quantitative assessment of non-enantioselective versus enantioselective interactions encountered in liquid chromatography on brush-type chiral stationary phase","volume":"1269","author":"Levkin","year":"2012","journal-title":"J. Chromatogr. A"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"693","DOI":"10.1055\/s-2001-12768","article-title":"Practical one-step synthesis of koga\u2019s chiral bases","volume":"5","author":"Cuthbertson","year":"2001","journal-title":"Synthesis"},{"key":"ref_13","unstructured":"Zief, M., and Crane, L. (1988). Chromatographic Chiral Separations, Marcel Dekker Inc."},{"key":"ref_14","unstructured":"Beesley, T.B., and Scott, R.P.W. (1998). Chiral Chromatography, John Willey & Sons."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1016\/S0021-9673(00)81419-3","article-title":"Effect of temperature on precision of retention measurements in liquid chromatography","volume":"194","author":"Gilpin","year":"1980","journal-title":"J. Chromatogr. A"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"4988","DOI":"10.1021\/jo00337a033","article-title":"Chiral HPLC (high-performance liquid chromatographic) stationary phases. 4. Separation of the enantiomers of bi-, beta-naphthols and analogs","volume":"46","author":"Pirkle","year":"1981","journal-title":"J. Org. Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"636","DOI":"10.1007\/BF02327662","article-title":"The role of the mobile phase in the resolution of racemic esters of aminoacids by normal phase high-performance liquid chromatography","volume":"25","author":"Akarya","year":"1988","journal-title":"Chromatographia"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"211","DOI":"10.1016\/S0021-9673(01)83490-7","article-title":"Practical supercritical fluid chromatography and extraction","volume":"351","author":"Yonker","year":"1986","journal-title":"J. Chromatogr."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2937","DOI":"10.1081\/JLC-100101834","article-title":"Influence of temperature on enantioseparation employing an amylose-derivative stationary phase","volume":"23","author":"Kazusaki","year":"2000","journal-title":"J. Liq. Chromatogr. Rel. Technol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1999","DOI":"10.1021\/ac961241l","article-title":"Mechanistic aspects of chiral discrimination on modified cellulose","volume":"69","author":"Crocker","year":"1997","journal-title":"Anal. Chem."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/19\/1\/9\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:51:31Z","timestamp":1760219491000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/19\/1\/9"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2013,12,19]]},"references-count":20,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2014,1]]}},"alternative-id":["molecules19010009"],"URL":"https:\/\/doi.org\/10.3390\/molecules19010009","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2013,12,19]]}}}