Bocian, Szymon

Buszewski, Bogusław

Krzemińska, Katarzyna

Skoczylas, Magdalena

English

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Solvation processes in liquid chromatography  - the importance and measurement Szymon Bocian, Magdalena Skoczylas, Katarzyna Krzemińska, Bogusław Buszewski  Chair of Environmental Chemistry & Bioanalytics, Faculty of Chemistry, Nicolaus Copernicus University, Toruń, Poland   Solvation is an indispensable part of the elution in liquid chromatography. The adsorption of solvents allows the elution of a solute from the adsorbent surface. The tendency for the adsorption of solvent molecules on the stationary phase surface results in the elution strength of a solvent. Therefore, the knowledge and the understanding of solvation process are crucial for the understanding of the retention mechanism of liquid chromatography separation.   Summarizing, the solvent from binary mobile phase interacts preferentially with the functional groups on the surface of the stationary phase. For understanding the distribution of the solvent between the stationary phase and a bulk binary solution the excess adsorption of the organic modifier has to be described. The presence of polar functional groups incorporated into the structure of bonded ligands changes the solvation process due to polar interactions and hydrogen bond creation.  The measurement of solvation process allows to calculate the number of silanols on silica surface. Acknowledgements This work was supported by Ministry of Science and Higher Education, Grant no. NCN 2013/09/D/ST4/03807 for period 2014–2017.  lIx ,1INTRODUCTION SELECTIVE SOLVATION SILANOLS CALCULATION INFLUENCE ON RETENTION CONCLUSIONS 0.0 0.2 0.4 0.6 0.8 1.0-0.50.00.51.01.52.02.53.03.54.0 Phenyl-amine Phenyl-amide Cogent-phenyl Phenoxy-propyl Phenyl-propyl Phenyl-hexylAcetonitrile excess amount [mol/m2]ACN volume fraction (0.0 0.2 0.4 0.6 0.8 1.00.00.20.40.60.81.01.21.41.61.8Methanol excess amount [mol/m2]MeOH volume fraction () Phenyl-amine Phenyl-amide Cogent phenyl Phenoxy-propyl Phenyl-propyl Phenyl-hexyl                                            0 2 4 6 8 10 12 14 1602000400060008000100001200014000Absorbance (µAU)Retention time (min) 50% ACN 60% MeOH0 1 2 3 4 5 6 7 8 90200040006000800010000120001400016000Absorbance (µAU)Retention time (min) 50% ACN 60% MeOH0 1 2 3 4 5020004000600080001000012000140001600018000Absorbance (µAU)Retention time (min) 50% ACN 60% MeOH0 1 2 3 4 5 6 7 80200040006000800010000120001400016000Absorbance (µAU)Retention time (min) 50% ACN 60% MeOH0 2 4 6 8 10 12 14 16 18 20 220200040006000800010000120001400016000Absorbance (µAU)Retention time (min) 50% ACN 60% MeOH0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0050001000015000200002500030000Absorbance (µAU)Retention time (min) 50% ACN 60% MeOHA                                                                                         B C                                                                                          D  E                                                                                          F Changes of solute retention causes by solvation process; benzene, anthracene, phenanthrene in isoeluotropic mobile phases conditions ACN/H2O (50/50v/v)  and MeOH/H2O (60/40v/v) on a series of phenyl-bonded stationary phases: Phenyl-amine (A), Phenyl-amide (B), Phenoxy-propyl (C), Phenyl Hydride (D), Phenyl-hexyl (E), Phenyl-propyl (F)                                                                                                                                                                                                                                                 0 1 2 3 4 5 6 7 8 90.00.51.01.52.02.53.03.54.04.5retention factor (k)maximum excess of adsorbed water [mmol/column] vitamin B6 tryptophanColumn Functional group Maximum excess of water [mmol/column] Amino-C3 aminopropyl 3.103 AP-C2 aminopropyl,  n-acylamide,  alkyl chains (C2) 0.989 AP-C12 aminopropyl,  n-acylamide,  alkyl chains (C12) 1.704 Amino-Cholesterol aminopropyl,  n-acylamide, cholesterol 0.640 Amino-P-C10 aminopropyl, phosphate, alkyl chains (C10) 3.351 Kinetex HILIC unbonded silica 2.288 Luna HILIC cross-linked DIOL 5.164 Venusil amide acylamide 6.546 TSK-gel Amide carbamoyl 8.301 SOLVATION vs. RETENTION IN HILC                                                                                                                                                                                                                                                 0,0 0,2 0,4 0,6 0,8 1,0-0,50,00,51,01,52,02,53,03,54,0MeOHExcess amount [mol/m2]methanol volume fraction [] NH2 CN Phenyl CH3                                                                                                                                                                                                                                                0,0 0,2 0,4 0,6 0,8 1,0-101234567891011 ACNExcess amount [mol/m2]acetonitrile volume fraction [] NH2 CN Phenyl CH3Stationary phase MeOH ACN ACN / MeOH ratio NH2 0.58 1.80 3.08 AP 1.36 3.30 2.42 Phenyl 0.32 1.94 5.99 CN 0.48 2.49 5.23 Chol 0.82 3.56 4.33 C18 0.41 1.88 4.59 C4 0.98 3.79 3.86 Theoretical solvent layers Silica gel Silanol groups concentration [μmol/m2] measured literature Kromasil 100 7.73 7.1 [1] 7.6 [2]  7.6-7.8 [3] 8±0.1 [4] 8.44±0.1 [5,6] 6.21 [7] Kromasil 300 8.06 Microsolv Technology 7.81 LiChrosorb Si 60 7.50 LiChrospher Si 100 8.55 Silpearl 6.13 SG 7/G 6.26 

Solvation processes in liquid chromatography  - the importance and measurement

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Solvation processes in liquid chromatography - the importance and measurement

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