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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. OGara,

    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

    Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    Understanding Stationary Phasesfor Reversed-Phase Separations:New Notions for a New Century

  • Dr. Pat McDonald

    [1980]Barbara Grover

    Joe Arsenault

    ChemicalProducts

    Analysis

    Evaluation

    Chem R&D

    Dr. Tom Walter

    SynthesisDr. John O'Gara

    Dr. Yuehong Xu

    Pam Richards

    Pam Iraneta

    Mark Capparella

    Bonnie Alden

    Dr. Chuck Phoebe Dr. Uwe NeueKimVanTran

    Applications

    Info Center

    Carla ClaytonGrace LavalleeMaureeen Allegrezza

    Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    Thank You Colleagues! 2

  • 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 particles 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".

    Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    3Abstract

  • N

    10 20 30 40 50 60 70 80 90 min

    Unexpected

    Note Peak Shape

    Expected

    4Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    1980 Curiosity Redux Discovery made by NOTwaiting for dry column

    to equilibrate.Same result 20 yrs later:

    Column: 3.9 x 150 mm; few pores > 100Sol-Gel Silica; fully C18 bondednot endcapped; air-dried > 1 yr

    Mobile Phase: 0.5 mL/min70% MeOH [good wetting]

    Injections: made every 1.5 min, startingas soon as 1st column volume emerges

    Quinoline[weak base]

  • 10 20 30 40 50 60 70 80 min

    N

    5Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    No Loss of EfficiencyColumn: Similar, except dried 18-20 hrs,argon stream, 80-90; injections 3 mins apart

    Super-dry column Quinoline peak

    shape degradationis NOT due toloss of efficiency.

    Constant tR fornaphthaleneindicatesNO changein phase ratio.

    Analyte-accessiblepores wet quickly.

  • 6

    10 20 30 40 50 60 70 80 min

    N

    Column: High Purity Synthetic Silica GelC18, endcapped; more surface area in larger pores4.6 x 150 mmdried 18-20 hrs, argon stream, 80-90

    Injections: 3 mins apartMobile Phase: 70% MeOH, 0.7 mL/min

    Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    Different Silica, Bonding

    Subtle, steady asymmetryincrease for quinoline peak.

    R2 = 0.9265

    R2 = 0.9482

    0.5

    1.0

    1.5

    2.0

    0 5 10 15 20 25 30 35

    Quinoline

    Naphthalene

    Injection Number

    Asymmetry

    No loss of efficiency, constant tR for naphthalene.

  • How much of the surface in a porous particlecan be accessed by: bonding reagents? solvents? analytes?

    What is ligand density in bonded phase?Where are surface silanols? Whats their role?Can modifications to surface or substrate

    structure be used to answer our questions?Traditional Cartoons are

    misleading, implyingincomplete coverage of

    accessible surface& direct analytesilanol

    access.

    7Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    Challenging Questions

    OSiOSiOHOSiOSiOHOSiOHOSiOSiOSiOH

    OSiOSi

    OSiOSiO

    OSiOSiO

    OSiO

    OSiOSiOSiO

    OSiOSi

    Mobile PhasepH > 3

    Mobile PhasepH < 3

    (CH3)2HN+

    NH(CH3)2+

    Surface

    Core

    Si

    O

    O O Si

    O

    O Si

    O

    O Si

    O

    O Si

    O

    O Si

    O

    OHOH

    OSi

    Si

    O

    O O

    O O Si

    O

    O

    Si

    O

    Si

    O

    Si

    O

    O Si

    O

    O O O O O O O

    OH OH OH

    SiO O Si O Si O Si O Si O Si OSiO O Si O Si

    Bonded Silica Par ticle

  • 8Ink bottles, craters, cylinders, plates are modelswhich lend themselves to simple math, BUT...

    REALITY is Geodesic-domed labyrinths formed withtetrahedral

    building blocks.ALL surfaceshave terminal

    SiOHgroups.

    Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    Silica Pore Structure

  • OHSi

    O OO

    SiO

    OHO

    SiO

    OHO

    Si O

    OO

    SiO

    SiO

    OH

    SiOH

    O

    SiO

    O

    O

    Si

    SiSi OH

    O OSi O

    OSi

    SiSi

    Si

    Si

    Si

    SiHOSi

    O

    SiO

    OSi

    O

    O

    Si OHO O

    Si Si

    Si

    SiOHO

    OSi

    SiO

    HOO

    SiO

    HO

    HO

    Si

    SiO

    SiO

    OO

    Si

    SiOH

    O

    OSi

    OHOO

    Si

    Si

    Si OH

    OOSi

    OO Si O

    OSi

    Si

    SiSi

    SiCH3CH3

    CH3

    SiH3C

    H3C

    CH3

    9Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    Pore Access Level 1Most accessible

    to largesilyl reagents

    under favorablereaction

    conditions;easiest-to-access

    surface reactsfirst &

    completely.

    Outer surface & surfacein pore spaces > ~100 in diameter nearest tooutside of particle

  • OHSi

    O OO

    SiO

    OHO

    SiO

    OHO

    Si O

    OO

    SiO

    SiO

    OH

    SiO

    O

    SiO

    O

    O

    Si

    SiSi OH

    O OSi O

    OSi

    SiSi

    Si

    Si

    Si

    SiOSi CH3

    H3C CH3

    Si CH3

    H3C CH3Si

    O

    SiO

    OSi

    O

    O

    Si OHO O

    Si Si

    Si

    SiOHO

    OSi

    SiO

    HOO

    SiO

    O

    HO

    Si

    SiO

    SiO

    OO

    Si

    SiH3C

    H3CH3C

    SiOH

    O

    OSi

    OHOO

    Si

    Si

    Si O

    OOSi

    OO Si O

    OSi

    Si

    SiSi

    SiCH3CH3

    SiCH3

    CH3CH3

    SiH3C

    H3C

    Poster by Patrick D. McDonald, Ph.D., HPLC 2001, Maastricht, 18-19 June 2001. 2001 Waters Corporation All photos 2001 by PDMcD. Waters, Bondapak, Symmetry, XTerra, HLPC, HydroLinked Proton Conduit are trademarks of Waters Corporation.

    Pore Access Level 2

    Accessible tosmaller silylendcapping

    reagents&

    solventmolecules

    Surface in pore spaces > ~50 directly connected to Level 1 pores.Diffusion distance fromouter surface is still minimal.

    10

  • OHSi

    O OO

    SiO

    OHO

    SiO

    OHO

    Si O

    OO

    SiO

    SiO

    OH

    SiO

    O

    SiO

    O

    O

    Si

    SiSi OH

    O OSi O

    OSi

    SiSi

    Si

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