Ion Chromatography

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Transcript of Ion Chromatography

  • 1Ion Exchange Chromatography

  • 2Components Same as any

    HPLC Instrument Reservoirs Pump Injector Column Detector Chromatography

    Software Specific

    Components Membrane

    Suppressor

  • 3Ion Exchange Chromatography

    Basic Separation Principle: Exchange equilibria between ions in solution and ions (of the same charge) held by surface bonded functional groups

  • 4Ion Exchange Functional Groups

    Cation Exchange Sulfonic acid SO3- (H+)

    Carboxylic Acid

    Anion Exchange Primary Amine NH3+(OH-)

    Tertiary Amine

    C O-(H+) =O

    N CH3

    CH3

    CH3

    +

    (OH-)

  • 5Mobil Phase

    Cation Exchange H+

    Anion Exchange - OH-

    pH is controlled with a Buffer Solution e.g. HCO3-/CO3--

  • 6Stationary Phase Ion Exchange Resin

  • 7Stationary Phase Solid Support Backbone

    CH CH2 CH CH2

    CH CH2

    styrene Divinylbenzene (DVB)

  • 8Polystyrene Divinylbenzene

    R R

    RR R

    CH CH2 CH CH2CH CH2

    CH CH2 CH CH2CH CH2 CH CH2

  • 91. Cellulose (the cellulose, derived from wood or cotton, is lightly derivatized with ionic groups to form the ion exchanger).

    Anion exchange

    Cation exchange

    2. Gel-type ion exchangers: combine the separation properties of gel filtration with those of ion exchange. Because of their high degree of substitution of charged groups, which results from their porous structures, these gels have a higher loading capacity than do cellulosic ion exchangers.

    Stationary Phase Ion Exchange Resin

  • 10

    Separation of Ca2+ Mg2+ Sr2+ and Ba2+

    Exchange equilibrium at the head of the column:2(R-SO3-H) + M2+ = (R-SO3)2-M + 2H+

    solid solution solid solution

    Separtion/Elution begins when acid solution is added Equilibrium shifts to the left Cation goes into the mobil phase (momentarily) Cation desorbs/re-adsorbs many times

  • 11

    The time the cation spends in each phase is governed by its unique value of Kexchange

    Rearranging gives:

    Separation of Ca2+ Mg2+ Sr2+ and Ba2+

    aq2

    solid2-

    3

    aq2

    solid2

    2-

    3reaction exchange

    ][M ]H[RSO][H M)[(RSOK ++

    ++= ]

    aq2

    solid2-

    3ex

    aq2

    solid2

    2-

    3

    ][H]H[RSO K

    ][MM)[(RSO

    ++

    +

    +=]

  • 12

    Separation of Ca2+ Mg2+ Sr2+ and Ba2+

    The terms on the r.h.s. are constant when:

    [H+]aq > [M+2]aq [RSO3-H]s > [(RSO3-)2M2+]si.e. [acid] > [cation] and binding sites are not saturated

    aq2

    solid2-

    3ex

    aq2

    solid2

    2-

    3

    ][H]H[RSO K

    ][MM)[(RSO

    ++

    +

    +=]

  • 13

    Separation of Ca2+ Mg2+ Sr2+ and Ba2+

    Normal Chromatography Separation Principles Apply:

    M

    SD

    aq2

    solid2

    2-

    3

    CC K

    ][MM)[(RSO ==+

    + ]

  • 14

    Ion Exchange Chromatography General Characteristics

    In general, ion exchangers favor binding of ions with: charge

    3+ > 2+ > 1+

    hydrated radius H+ > Li+ > Na+ > K+ (p. 174) H+ bound least strongly b/c hydrated radius is

    highest

    polarizability

  • 15

    ExampleChromatograms

    Cation Exchange Anion Enchange

  • 16

    Example Chromatograms

  • 17

    Illustration of Ion Exchange Chromatography

    Slide Number 1ComponentsIon Exchange ChromatographyIon Exchange Functional GroupsMobil PhaseStationary Phase Ion Exchange ResinStationary Phase Solid Support BackbonePolystyrene DivinylbenzeneStationary Phase Ion Exchange ResinSeparation of Ca2+ Mg2+ Sr2+ and Ba2+Separation of Ca2+ Mg2+ Sr2+ and Ba2+Separation of Ca2+ Mg2+ Sr2+ and Ba2+Separation of Ca2+ Mg2+ Sr2+ and Ba2+Ion Exchange Chromatography General CharacteristicsExampleChromatogramsExample ChromatogramsIllustration of Ion Exchange Chromatography