离子色谱法简介 英文版_59页.pdf

ic_theory_20041011_e.ppt 1ICICICICICAn introduction to Ion ChromatographyAn introduction to Ion ChromatographyTheory of ICK.H.ViehwegerMetrohm AG,Herisau,Switzerland ic_theory_20041011_e.ppt 2ICICICICICWhat is chromatography?What is chromatography?about history and physical chemistry Where does the chromatography actually happen?Where does the chromatography actually happen?from ion exchange to ion pairsWhich detection can be used?Which detection can be used?from voltammetry to conductivityWhat is suppressed ion chromatography?What is suppressed ion chromatography?from high to low backgroundsChromatographyChromatography?from beginners to expertsContentContentTheory of IC ic_theory_20041011_e.ppt 3ICICICICICDefinitionDefinitionAn analytical method where a substance mixture appearing in just one colour is separated in a way that different colours become visible.The method is used to separate chemical substances which are chemically quite similar and though difficult to separateGreekchroma=colourgraphein=to writeHistoryHistoryTheory of IC ic_theory_20041011_e.ppt 4ICICICICIC18501935194219471953195719591967-70197519791976-80topsoilssulfonated and aminated polymerssulfonated polystyrene/divenylbenzene resins(Manhattan project)aminatedion exclusion chromatographymacro pore iotheoretical backgroundpelicular ion exchange materialsion exchange chromatography wdetectioconducsuppressionion pair chromatographyas ion exchanger for Mg2+,Ca2+and NH4+PS/DVB resins as ion exchangern exchangerith conductivity n and stripper(suppressor)tivity detection with electronicThomson,WayAdams,HolmsdAlelioMcBurneyWheaton,BaumannCorte,Meyer et al.HelfferichHorvath,KirklandSmall,StevensGjerde,FritzWaters,Bidlingmeier,et.al,Baumann,SchmucklerLCHPLCHistoryHistoryTheory of IC ic_theory_20041011_e.ppt 5ICICICICICtake a piece of papermake a little drop with black inkjust add water to its centersee the colors that make upthe blackinkGoing back to schoolGoing back to schoolChromatographyA simple experiment from schoolA simple experiment from school ic_theory_20041011_e.ppt 6ICICICICICDefinitionDefinitionThe term chromatography is the general name for a wide range of physico-chemical separation processes in which the components to be separated are distributed between a stationary and a mobile phase.gaseousmobile phasemobile phaseliquidstationary phasestationary phaseliquid GLC,LLCsolid GSC,LSC(HPLC-IC)Physico Physico chemicalchemicalChromatography ic_theory_20041011_e.ppt 7ICICICICICTypes of chromatographyTypes of chromatographyMobile phase dissolves and transports the analyteStationary phase retains the analyteadsorbing adsorption chromatographydissolving distribution chromatographyreacting ion exchangechromatographyColumn interactionsColumn interactionsChromatography ic_theory_20041011_e.ppt 8ICICICICICMethods of chromatographyMethods of chromatographyBased on the polarities of the stationary and mobile phases a distinction is made between the following methods:Group 1 traditional TLC+HPLC1.normal phase chromatography2.reversed phase chromatographyGroup 2 Ion Chromatography4.ion exchange chromatography3.ion pair chromatography5.ion exclusion chromatographyPolaritiesPolaritiesChromatography ic_theory_20041011_e.ppt 9ICICICICICGroup 1 Group 1 traditional TLC+HPLCtraditional TLC+HPLC1.Normal phase chromatographyStationary p.=polar(e.g.SiO2)mobile p.=non polar(e.g.n-hexane)2.Reversed phasechromatographyStationary p.=non-polar(e.g.C18)mobile p.=polar(e.g.acetonitrile or methanol/water)Traditional methodsTraditional methodsChromatography ic_theory_20041011_e.ppt 10ICICICICICGroup 2 Group 2 ICIC4.Ion exchange chromatographyCations and anions form a weak ionic binding with the stationary phase.C:Stationary p.=polar(e.g.R-SO3)mobile p.=polar(e.g.HNO3aq.)orA:Stationary p.=polar(e.g.R-NR3+)mobile p.=polar(e.g.Na2CO3aq.)IC methodsIC methodsChromatography ic_theory_20041011_e.ppt 11ICICICICICGroup 2 Group 2 ICIC3.Ion pair chromatographyCations and anions react to a non-ionic molecule by adding a lipophilic counter ion.The resulting non-polar molecules are then separated in the RP-mode.Stationary p.=non-polar(e.g.C18)mobile p.=polar(e.g.acetonitrile or methanol/water)IC methodsIC methodsChromatography ic_theory_20041011_e.ppt 12ICICICICICGroup 2 Group 2 ICIC5.Ion exclusion chromatographyBy adding H+-ions the stationary phase is transformed into a non ionic but polar Donan membrane.Only non dissociated molecules can enter this membrane.If they dissociate they are excluded from the stationary phase.The separation is though depending on the dissociation constant of the respective molecules.mobile p.=polar(e.g.H2SO4aq.)IC methodsIC methodsChromatography ic_theory_20041011_e.ppt 13ICICICICICDefinitionDefinitionIon chromatography includes all chromatographic methods that separate ionic substances and substances that dissociate easily.These methods are ion pair chromatography(3),ion exchange chromatography(4)and ion exclusion chromatography(5).Analyte and mobile phase are initially always polar and/or ionic.Ion exchange chromatography is the most important separation mechanism in ion chromatography.ResumeResumeChromatography ic_theory_20041011_e.ppt 14ICICICICICLiquidLiquid-solidsolid-chromatographychromatographySince the introduction of high pressure or high performance chromatography(HPLC)at the end of the sixties,liquid chromatography has developed into one of the most comprehensive and important methods of modern instrumental analysis.Ion chromatography is an aliquot of the HPLC-family.mobile phase=liquid and stationary phase=solidHPLC and ICHPLC and ICChromatography ic_theory_20041011_e.ppt 15ICICICICICEluentPump Injector ColumnSuppressorDetectorMost popular set upMost popular set upChromatography ic_theory_20041011_e.ppt 16ICICICICICEluentPump Injector ColumnDetectorWhere does it actually happen?Where does it actually happen?Chromatography ic_theory_20041011_e.ppt 17ICICICICICThe stationary phaseThe stationary phase?Cations need a cation exchanger and anions need an anion exchanger?How a stationary phase is builtStyreneDivinylbenzeneCationexchangerIon exchangeIon exchangeChromatographyStyrene-divinylbenzene resinAnionexchanger ic_theory_20041011_e.ppt 18ICICICICICComposition of the Composition of the stationary phasestationary phaseSubstrates?Polystyrene/divinylbenzene?Polymethacrylate?Polyalcohol?Hydroxyethylmethacrylate(HEMA)?SilicateAnion exchanger?quaternary ammonium groups?alkyl amines?hydroxy-alkylamines?alkyl amines with acrylate type crosslinkingIon exchangeIon exchangeChromatography?substrate/resin carrier?a spacer group?a group that carries the separating capacityCation exchanger?sulfonates?carboxylatesSpacer?alkyl chain ic_theory_20041011_e.ppt 19ICICICICICMobile PhaseMobile Phase?The mobile phase dissolves and carries the sample?The mobile phase is usually aqueousanions(I)?Phthalic acid?Salicylic acid?p-Hydroxybenzoic acid?Benzoic acid?Borate?Borate/Gluconate?Potassium hydroxide.anions(II)?Carbonat/bicarbonate?Potassium hydroxide?Boratecations(I)?Nitric acid?Tartaric acid?Tartaric acid/dipicolinic acid?Tartaric acid/citric acid?Sodium dihydrogene phosphate?oxalic acid/ethylene diamine/acetone.Ion exchangeIon exchangeChromatography ic_theory_20041011_e.ppt 20ICICICICICIon exchangeIon exchangeChromatographyCationCation separation mechanismseparation mechanismStationary phase and mobile phase compete for the analyte ic_theory_20041011_e.ppt 21ICICICICICC2 250Tartaric-/dipicolinic acid/crown ether;4/0.45/0.05 mmol/L1LithiumSodiumNH4+4MEA1.05DEA1.06Potassium4.87TEA5.08MDEA4.89Calcium5.010Magnesium0.521.034.01.0Ion exchangeIon exchangeChromatographyppmCationsCations ic_theory_20041011_e.ppt 22ICICICICICIon exchangeIon exchangeChromatographyIIIIIIIIIIVIVV VVIVIVIIVIIVIIIVIIII III IIIIIIVVVIVII VIIIHHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcKuCationsCations(selected)(selected)ic_theory_20041011_e.ppt 23ICICICICICAnion separation mechanismAnion separation mechanismStationary phase and mobile phase compete for the analyteIon exchangeIon exchangeChromatography ic_theory_20041011_e.ppt 24ICICICICICA Supp 5 250NaHCO3/Na2CO3;1/3.2 mmol/L1FluorideChloriteBromate4Chloride5.05Nitrite5.07Chlorate5.08Bromide5.09Nitrate5.010Phosphate5.011Sulfate5.025.035.05.0Ion exchangeIon exchangeChromatographyppmAnionsAnions ic_theory_20041011_e.ppt 25ICICICICICIon exchangeIon exchangeChromatographyIIIIIIIIIIVIVV VVIVIVIIVIIVIIIVIIII III IIIIIIVVVIVII VIIIHHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcKuAnions(selected)Anions(selected)ic_theory_20041011_e.ppt 26ICICICICICCationsCations?Cations interact with the basic ion-exchange sites of the stationary phase.According to the strength of binding(ion exchange equilibrium constant)these will be eluted earlier or later by the following protons from the eluent.Anions Anions?Anions interact with the acidic ion-exchange sites of the stationary phase.According to the strength of binding(ion exchange equilibrium constant)these anions will be eluted earlier or later by the following carbonate ions from the eluentSeparation?Different ion exchange equlibrium constants lead to different retention times of the respective cations or anions and that means separation of the substances which are chemically quite similar.Ion exchangeIon exchangeChromatography ic_theory_20041011_e.ppt 27ICICICICICIon exclusionIon exclusionChromatographyAnion separation mechanismAnion separation mechanismLipophilic interaction between analyte and stationary phase ic_theory_20041011_e.ppt 28ICICICICICMetrosep Organic AcidsPerchloric acid;0.5 mmol/L1LactateFormateAcetate4Propionate1.05Butyrate1.07iso-Butyrate1.08Valerate1.09iso-Valerate1.021.031.01.0Ion exclusionIon exclusionChromatographyppmOrganic acidsOrganic acids ic_theory_20041011_e.ppt 29ICICICICICMobile PhaseMobile Phase?Anions are excluded and elute with the void volume in the solvent front.Anions of organic acids form with protons weak organic acids.These acids are only to a small degree dissociated and have a low polarity.Stationary phaseStationary phase?On the ion exchanger a Donan membrane is formed.This membrane has a low polarity.InteractionInteraction?As long as the organic acids are not dissociated they can stay in the Donan membrane.If they are dissociated they become ionic.In this case they are excluded from membrane.Attention!Attention!?Cations will be separated by ion exchange and therefore may disturb the chromatogram.Ion exclusionIon exclusionChromatography ic_theory_20041011_e.ppt 30ICICICICICIon pairIon pairChromatographyCationCation and anion separation mechanismand anion separation mechanismRP reversed phase mechanism ic_theory_20041011_e.ppt 31ICICICICICMobile PhaseMobile Phase?The mobile phase is of high polarity(e.g.acetonitrile or methanol/water)Stationary phaseStationary phase?The stationary phase(e.g.C18)is of low polarity a type of RP-Phase.CationsCations?Analyte cation(e.g.Na+)plus lipophilic anion(e.g.alkyl sulphonic acid)form a non polar moleculeAnionsAnions?Analyte anion(e.g.Cl)plus lipophilic cation(e.g.tetra butyl ammonium)form a non polar molecule?The lipophilic end of the modified anion or cation molecule interact with the stationary phase in the RP-mode.This interaction leads to different retention times and that means separation of substances which are chemically quite similar.Ion pairIon pairChromatography ic_theory_20041011_e.ppt 32ICICICICICEluentPump Injector ColumnDetectorDetectionDetectionChromatography ic_theory_20041011_e.ppt 33ICICICICIC?Conductivity detector?Amperometric detector?UV/VIS detector(optical)?RI detector(optical)?IC/MSTypes of detectionTypes of detectionDetectionDetectionChromatography ic_theory_20041011_e.ppt 34ICICICICICMeasuring principleMeasuring principleA defined decent potential is applied to a three electrode system consisting of reference-,working-and auxiliary-electrode.If any oxidizable substance pass these electrodes an oxidation process takes place.A current corresponding to the concentration of the respective substance is measured.ElectrochemicalElectrochemicalDetectionSimple connection to any IC-or HPLC-system?Large variety of electrode materials(glassy carbon,carbon paste,silver,gold,etc.)?Highly sensitive?Very selective?Excellent price/performance ratio ic_theory_20041011_e.ppt 35ICICICICICCharacteristicsCharacteristics?Sensitive to UV-active ions e.g.nitrite,nitrate,thiosulfate?Almost no interference by non-chromophoric ions e.g.chloride,sulphate?Eluent must be UV-transparent?Limited possibilities of organic modifiersUV/VISUV/VISDetection ic_theory_20041011_e.ppt 36ICICICICICCharacteristicsCharacteristics?UV-adsorbing eluent e.g.phthalic acids?All ions with no adsorbance at the UV-wavelength applied aredetected?Detector must be extremely sensitive because measurements are performed with very low light intensity?Sensitivity is lower than the sensitivity achieved by conductivity detectionUV/VIS indirectUV/VIS indirectDetection ic_theory_20041011_e.ppt 37ICICICICICCharacteristicsCharacteristics?Selective determinations?Time consuming(wet chemistry is needed)?More complex system?Additional peak broadening?Last possibility if all other approaches fail UV/VIS with UV/VIS with pcrpcrDetection ic_theory_20041011_e.ppt 38ICICICICICCharacteristicsCharacteristics?Qualitative and quantitative information?Determination of single atoms?Determination of molecule fragments?Expensive set up?High operating costsIC/MSIC/MSDetection+QuadrupoleLensesFragmentation zone(CID)IC outletSkimmersCapillaryOctopoleDetector ic_theory_20041011_e.ppt 39ICICICICICWhat is What is conductometryconductometry?Conductometry is the measurement of conductivity a conductometricdetector measures the electrical conductivity of ions in a solution.This is done by applying an electrical field between two electrodes.The ions migrate in this field.The anions migrate to the anode and the cations to the cathode.The electrical resistance of the solution is measured.The conductivity is the reciprocal of the resistance.Alternating current is used in order to avoid substance changes and the formation of diffusion boundary layers at the electrodes.=1RcK*R=resistance Kc=cell constant 1/cm =specific conductivity 1/or SConductivityConductivityDetection ic_theory_20041011_e.ppt 40ICICICICICWhat is specific conductivity?What is specific conductivity?The specific conductivity of an eluting ion depends on the concentration c of the individual ions i,the charge Zi,and the equivalent conductivity i.The equivalent conductivity iis a concentration-dependent quantity.The values listed can be applied for concentrations below 0.001 mol/L.Ziis the charge of the respective ion.i=equivalent conductivity S cm2/molzi=charge ci=concentration mol/L =specific conductivity 1/or S=sum of all ions anions and cations=(*)iiizcConductivityC