Column Separation (liquid-liquid, Liquid-solid) Used For .

High Performance Liquid Chromatography (HPLC)Column separation (liquid-liquid, liquid-solid) used for separatingand analyzing compounds based on differences in theirinteraction with a stationary phase.Adsorption, partition, ion exchange, molecular exclusion and affinity

The ChromatogramAmobile AStationaryK DVs tr tmk' VmtmL tr N 16 H w 2Remember, relating the peak height or area to an injected analyteconcentration requires a response curve obtained under the sameseparation conditions.

When analytes are not volatile then?There are many different ways to use liquid chromatography to separatecompounds of interest and the choice of technique usually depends onthe physicochemical characteristics of the molecule of interest. The solidphases used for each type of chromatography are highly engineeredporous, chemically inert supports functionalized with various chemicalgroups that determine the interactions with the molecules to beseparated.Commonly used modes of separation are based on: Specific binding interactions (affinity chromatography) Charge (ion exchange chromatography) Size (size exclusion chromatography/gel filtration chromatography) Hydrophobic surface area (hydrophobic interaction chromatographyand reverse phase chromatography) Multiple properties (multimodal or mixed-mode ations-technologies/types-chromatography

Affinity ChromatographyAffinity chromatography is a separation method based on a specificbinding interaction between an immobilized ligand and its bindingpartner. Examples include antibody/antigen, enzyme/substrate, andenzyme/inhibitor interactions. The degree of purification can be quitehigh depending on the specificity of the interaction and, consequently, itis generally the first step, if not the only step, in a purification strategy.The molecule of interest can then be released from the resin using a buffer with ahigh salt concentration, a pH shift, or a competing echnologies/types-chromatography

Ion Exchange ChromatographyIon exchange chromatography involves the separation of ionizable moleculesbased on their total charge. This technique enables the separation of similartypes of molecules that would be difficult to separate by other techniquesbecause the charge carried by the molecule of interest can be readilymanipulated by changing buffer pH.Depending on the pH of their environment, proteins may carry a netpositive charge, a net negative charge, or no charge. The pH at which amolecule has no net charge is called its isoelectric point, or ologies/types-chromatography

Ion Exchange ChromatographyIon exchange chromatography is a technique that is used analytically unlikesome other separation methods that are used more for preparative purposes.Example shows a series of proteins separated and eluted off the column withincreasing salt content in the mobile phase. Site competition!Increasing salt technologies/types-chromatography

IEC Stationary Phase TypesStrong ion exchangers are often preferred resins for many applicationsbecause their performance is unaffected by pH. However, weak ionexchangers can be powerful separation tools in cases where strong ionexchangers fail because the selectivities of weak and strong ion exchangersoften differ.SupportDEAEHigh QCMHigh SType ofexchangeWeak anionStrong anion Weak cationFunctionalgroup-N (C2H5)2-N (CH3)3-SO3--COO-pH Range*5–90–145–90–14Strongcation

Size Exclusion ChromatographySize exclusion chromatography (SEC), also called gel filtrationchromatography, separates molecules based on their sizes. SEC resins aregels that contain beads with a known pore size. When a complex proteinmixture is passed over SEC resin, small molecules move through the beadpores, whereas molecules too large to fit into the pores move around thebeads and through the void space between beads.When dissolved molecules of various sizesflow into the column, smaller dissolvedmolecules flow more slowly through thecolumn because they penetrate deep intothe pores, whereas large dissolvedmolecules flow quickly through the columnbecause they do not enter the pores.Purification chnologies/types-chromatography

Normal- and Reversed-Phase HPLCA molecule’s structure, activity, and physicochemical characteristics aredetermined by the arrangement of its constituent atoms and the bondsbetween them. Within a molecule, a specific arrangement of certain atomsthat is responsible for special properties and predictable chemical reactionsis called a functional group. This structure often determines whether themolecule is polar or non-polar.Separations based on an analytes relative affinity for the mobile phaseversus the stationary phase. Polar vs. non-polar.http://www.waters.com/waters/en US/HPLC-Separation-Modes/nav.htm?cid 10049076&locale en US

Normal- and Reversed-Phase HPLCStationary phases are commonly bonded to a high surface area, inert support (silica).To summarize, the chromatographer will choose the best combination of a mobilephase and particle stationary phase with appropriately opposite polarities. Then, asthe sample analytes move through the column, the rule like attracts like willdetermine which analytes slow down and which proceed at a faster speed.http://www.waters.com/waters/en US/HPLC-Separation-Modes/nav.htm?cid 10049076&locale en US

Normal-Phase HPLCIn the separations of plant extracts, Tswett (original developer ofseparation science) was successful using a polar stationary phase with amuch less polar [non-polar] mobile phase. This classical mode ofchromatography became known as normal phase.The figure represents a normal-phase chromatographic separation of a threedye test mixture. The stationary phase is polar and retains the polar yellow dyemost strongly. The relatively non-polar blue dye is won in the retentioncompetition by the mobile phase, a non-polar solvent, and elutes quickly. Sincethe blue dye is most like the mobile phase [both are non-polar], it moves faster.It is typical for normal-phase chromatography on silica that the mobile phase is100% organic; no water is used.http://www.waters.com/waters/en US/HPLC-Separation-Modes/nav.htm?cid 10049076&locale en US

Reversed-Phase HPLC (most common method)The term reversed-phase describes the chromatography mode that is justthe opposite of normal phase, namely the use of a polar mobile phase anda non-polar [hydrophobic] stationary phase. The figure illustrates theblack three-dye mixture being separated using such a protocol.Now the most strongly retained compound is the more non-polar bluedye, as its attraction to the non-polar stationary phase is greatest. Thepolar yellow dye, being weakly retained, is won in competition by thepolar, aqueous mobile phase, moves the fastest through the bed, andelutes earliest like attracts like.http://www.waters.com/waters/en US/HPLC-Separation-Modes/nav.htm?cid 10049076&locale en US

Reversed-Phase HPLC (most common method)Because it is more reproducible and has broad applicability, reversedphase chromatography is used for approximately 75% of all HPLCmethods. Most of these protocols use as the mobile phase an aqueousblend of water with a miscible, polar organic solvent, such asacetonitrile or methanol. This typically ensures the proper interaction ofanalytes with the non-polar, hydrophobic particle surface. A C18–bondedsilica [sometimes called ODS] is the most popular type of reversed-phaseHPLC packing.http://www.waters.com/waters/en US/HPLC-Separation-Modes/nav.htm?cid 10049076&locale en US

Types of NP and RP-HPLC: Adsorption MechanismSilica, SiO2 xH2OAlumina, Al2O3 xH2OSolvent molecules completewith solute molecules forsites. More strongly thesolvent binds to the statphase, the greater the eluentstrength.

Adsorption Chromatography

Types of NP and RP-HPLC: Partition MechanismThis form of chromatography is based on a thin film formed on thesurface of a solid support by a liquid stationary phase. Solute equilibratesbetween the mobile phase and the stationary liquid.Solutes dissolved in mobilephaseNon-volatile liquid stat. phasePartition or transfer of an analyte in and out of a liquid stationary phase.

RP-HPLC: Retention OrderReversed phase HPLC is characterized by a situation in which the mobile phase usedis MORE POLAR than the stationary phase.More polar analytes elute first, less polar analytes are retained longer. Waterand miscible organics (acetonitrile, methanol, ethanol) make for a polarmobile phase. Analytes must be soluble in mobile phase!!!

NP-HPLC: Retention OrderIn normal-phase chromatography, the stationary phase is polar and the mobilephase is nonpolar.Silica is the preferredstationary phase mainlybecause its availability, knownperformance and low cost.A variety of polar bondedphases are used withfunctional groups such ascyano [-(CH2)3CN], amino [(CH2)nNH2], diol, bonded tothe silica stationary phase.Least polar analytes elute first, more polar analytes are retained longer. Lowto medium polarity solvents are used (hexane, ethyl acetate, methanol). Musteliminate water. Analytes must be soluble in mobile phase!!!

Summary of NP and RP-HPLCTypeMobile PhaseStationary PhaseElution OrderNormal PhaseNon-polar(hexane,toluene,methanol)Polar (silica or chemicallymodified Si such as –O-(CH2)3-CN)Least polarfirst, mostpolar lastReversedPhasePolar (water miscibleorganic solvent(acetonitrile,ethanol,methanol)Non-polar (chemically-modifiedsilica, C8, C12, C18 groups)Most polarfirst, leastpolar last5 μm diam. particle sizeRemember: The analytes must be soluble in the mobile phase in order to use theseparation method and the longer the analytes spend interacting with thestationary phase, the broader the peaks will be.

Type Mobile Phase Stationary Phase Elution Order Normal - Phase Non-polar (hexane, toluene, methanol) Polar (silica or chemically-modified Si such as –O-(CH 2) 3-CN) Least polar first, most polar last Reversed-Phase Polar (water miscible organic solvent (acetonitrile, ethanol, methanol) Non-polar (chemically-modified