Understanding Stationary Phases for Reversed-Phase ... · PDF fileUnderstanding Stationary Phases for Reversed-Phase Separations: New Notions for a New Century. Dr. Pat McDonald ...
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Patrick D. McDonald*, Bonnie A. Alden,KimVan Tran, Charles H. Phoebe, Jr.,Pamela C. Iraneta, Mark Capparella,Thomas H. Walter, Uwe D. Neue,Barbara K. Grover, John E. O’Gara,
Joseph C. Arsenault, Yuehong Xu, Pamela A. Richards*[email protected]
Waters Corporation, 34 Maple Street, Milford, MA USA 01757Poster: HPLC 2001 Maastricht, 18-19 June 2001
Experiments designed to explore the actual physical reality of the interaction of mobile andstationary phases are fraught with practical limitations that impede drawing significantconclusions from the results. It has been easier for most practitioners to foster the folkloreforged through the citation generations of HPLC literature than to refine the "cartoon-level"view of the chromatographic process to a higher "art".
Hybrid Particle Technology enables creation of chromatographic substrates with interesting,specifically designed chemical modifications that reside not simply at the "accessible" surface,but, rather, throughout the entire backbone of a particle’s molecular make-up.This now permits rational exploration of structure-activity relationships with a view towardunderstanding and explaining observations that previously seemed incongruous.Accessible-surface modifications in the traditional manner add further variables to the studyof the ways in which analyte molecules interact with the mobile and stationary phaseson their "random walk" through the chromatographic bed.
Results of experiments using both bonded-silica phases and new bonded-hybrid particle phases,allied with recent ideas from related disciplines, will be shown to challenge traditionalconcepts of accessible surface, ligand density, silanol interaction, and hydrophobic "collapse".Particular attention will be paid to the role of the structure and physicochemical propertiesof both particle substrate and mobile phase elements as they, together,determine the constitution and function of the "stationary phase".
Recent Studies in Semiconductor FieldChallenge Myth that High Ligand
Densities on Silica SurfacesCannot Be Achieved:
“Very strong molecule–substrate interactions...result in... formation of chemical bonds...at the interface, molecules try to occupy every available binding site on thesubstrate...in this process they push together molecules that have already adsorbed,thus eliminating free volume....in all SA monolayers the spontaneous adsorptionat the organic material–substrate interface,together with the strong van der Waals attraction amongst the alkyl chains,are the driving force for the formation of highly ordered,and closely packed systems.”*
New Notions - Summary• Pore surface area accessibility is key to effective
surface modification & RP HPLC performance.• Ligand density may reach maximum in accessible
pores – total surface area calculation is misleading.• Pore dewetting, not hydrophobic collapse,
causes retention loss.• Silanols, even in micropores, may affect analytes
via water wires.• Water wires may be disrupted by embedded polar
groups, inhibited by hybrid particle pores.• Hybrid particle technology holds promise for
stationary phase performance improvements.
24aWaters Authors•Observations on the Wetting of HPLC Packings, T Walter, P Iraneta, M Capparella, Poster #P-202/A, HPLC’97, Birmingham
(1997) 19 pp [http://www.waters.com/pdfs/TWHPLC97.pdf or Search Waters Applications Library for 980947]•Dependence of cyano bonded phase hydrolytic stability on ligand structure and solution pH, JE O’Gara, BA Alden, CA
Gendreau, PC Iraneta, TH Walter, J Chromatogr A 893(2) (2000) 245-251•Systematic Study of Chromatographic Behavior vs Alkyl Chain Length for HPLC Bonded Phases Containing an Embedded
Carbamate Group, JE O’Gara, DP Walsh, BA Alden, P Casellini, TH Walter, Anal Chem 71(15) (1999) 2992-2997•Improving Our Understanding of Reversed-Phase Separations for the 21st Century, PD McDonald et al., Lecture #154,
ISC 2000, London, 3 Oct 2000Proton Transfer & Protein Pumps, Hydrogen Bonding in Water•The Dynamics of Proton Transfer in a Water Chain, RR Sadeghi, H-P Cheng, J Chem Phys 111(5) (1999) 2086-2094•Lehninger Principles of Biochemistry, 3rd ed, http://www.worthpublishers.com/lenhinger3d/iindex.html•Comment on the mechanism of proton-coupled electron transfer reactions, S-I Cho, S Shin, J Molecular Structure 499 (2000)
1-12•Time-Resolved Dynamics of Proton Transfer in Proteinous Systems, M Gutman, E Nachliel, Annu Rev Phys Chem 48 (1997)
329-356•Biophysical aspects of intra-protein proton transfer, S Brandsburg-Zabary, O Fried, Y Marantz, E Nachliel, M Gutman, Biochim
Biophys Acta 1458 (2000) 120-134•Ab initio analysis of proton transfer dynamics in (H2O)3H
+, PL Geissler, C Dellago, D Chandler, J Hutter, M Parrinello, ChemPhys Lett 321 (2000) 225-230
•Interactions of Hydration Water and Biological Membranes Studied by Neutron Scattering, J Fitter, RE Lechner, NA Dencher, JPhys Chem B 103 (1999) 8036-8050
•A direct-dynamics study of proton transfer through water bridges in guanine and 7-azaindole, Z Smedarchina, W Siebrand, AFernández-Ramos, L Gorb, J Leszczynski, J Chem Phys 112(2) (2000) 566-573
•Oxygen and Proton Pathways in Cytochrome c Oxidase, I Hofacker, K Schulten, PROTEINS: Structure, Function, & Genetics30 (1998) 100-107
•The dynamics of hydrogen bonds and proton transfer in zeolites - joint vistas from solid-state NMR and quantum chemistry, HKoller, G Engelhardt, RA van Santen, Topics in Catalysis 9 (1999) 163-180
24b•How water takes shape at hydrophobic surfaces, GL Richmond, C&EN, Sept 11 (2000) 29•Autoionization in Liquid Water, PL Geissler, C Dellago, D Chandler, J Hutter, M Parrinello, Science 291 (16 Mar 2001) 2121-
2124•An Introduction to Hydrogen Bonding, GA Jeffrey, Oxford University Press, New York (1997) pp 119-123•The Structure and Properties of Water, D Eisenberg, W Kauzmann, Oxford University Press, New York (1969) pp 225-227
Monolayers, Surfaces, Pores•Self-Assembled Monolayers of Alkyltrichlorosilanes: Building Blocks for Future Organic Materials, A Ulman, Adv Mater 2(12)
(1990) 573-582•Self-Assembled Mono- and Multilayers of Terminally Functionalized Organosilyl Compounds on Silicon Substrates, S Heid, F
Effenberger, Langmuir 12 (1996) 2118-2120•Formation of Uniform Aminosilane Thin Layers: An Imine Formation to Measure Relative Surface Density of the Amine Group,
JH Moon, JW Shin, SY Kim, JW Park, Langmuir 12 (1996) 4621-4624•Pore-Resolved NMR Porosimetry, RS Drago, DC Ferris, DS Burns, J Am Chem Soc 117 (1995) 6914-6920•The Surface Tension Components of Aqueous Alcohol Solutions, B Janczuk, T Bialopiotrowicz, W Wojcik, Colloids Surfaces
36 (1989) 391-403
Reversed-Phase HPLC•Solvophobic Interactions in Liquid Chromatography with Nonpolar Stationary Phases, C Horváth, W Melander, I Molnár, J
Chromatogr 125 (1976) 129-156•The Molecular Mechanism of Retention in Reversed-Phase Liquid Chromatography, JG Dorsey, KA Dill, Chem Rev 89 (1989)
331-346•Retention in reversed-phase chromatography: partition or adsorption?, A Vailaya, C Horváth, J Chromatogr A 829 (1998) 1-27•Revisionist look at solvophobic driving forces in reversed-phase liquid chromatography, PW Carr, J Li, AJ Dallas, DI Eikens, LC
24cSilica & Bonded Phases•Porous Silica, KK Unger, J Chrom Library, 16 Elsevier (1979) 359 pp•Synthesis of spherical porous silicas in the micron and submicron size range: challenges and opportunities for miniaturized
high-resolution chromatographic and electrokinetic separations, KK Unger, D Kumar, M Grün, G Büchel, S Lüdtke Th Adam,K Schumacher, S Renker, J Chromatogr A 892 (2000) 47-55
•A Geometrical Model for Chemically Bonded TMS and PDS Phases, GE Berendsen, L de Galan, J Liq Chromatogr 1(4) (1978)403-426
•Preparation and Chromatographic Properties of Some Chemically Bonded Phases for Reversed-Phase Liquid Chromatography,GE Berendsen, L de Galan, J Liq Chromatogr 1(5) (1978) 561-586
•Preparation of Various Bonded Phases for HPLC Using Monochlorosilanes, GE Berendsen, KA Pikaart, L de Galan, J LiqChromatogr 3(10) (1980) 1437-1464
•Determination of Bonded Phase Thickness in Liquid Chromatography by Small Angle Neutron Scattering, LC Sander, CJGlinka, SA Wise, Anal Chem 62(10) (1990) 1099-1101
•Geometry of Chemically Modified Silica, I Rustamov, T Farcas, F Ahmed, F Chan, R LoBrutto, HM McNair, YV Kazakevich, JChromatogr A [HPLC 2000 Proceedings Volume] in press
•Interpretation of the Excess Adsorption Isotherms of Organic Eluent Comoponents on the Surface of Reversed-PhaseAdsorbents. Effect on the Analyte Retention, YV Kazakevich, R LoBrutto, F Chan, T Patel, J Chromatogr A [HPLC 2000Proceedings Volume] in press
•Chromatographic silanol activity test procedures: the quest for a universal test, SD Rogers, JG Dorsey, J Chromatogr A 892(2000) 57-65
Other key references cited in footnotes on individual pages.