Analysis of Analgesic Tablets by Thin Layer Chromatography (TLC)Separating MoleculesThin Layer ChromatographyHow the separation worksHow this works, continued“Nuts and Bolts” of the MethodRf ValuesCalculating an Rf ValueAnalgesic MedicationsActivesProcedureProcedure, con’tWhat your TLC Plate will Look LikeProcedure (con’t)TLC TankDevelopingResultsResults IIConclusions: Things to Think AboutAnalysis of Analgesic Tablets by Analysis of Analgesic Tablets by Thin Layer Chromatography (TLC)Thin Layer Chromatography (TLC)Organic Chemistry Lab IOrganic Chemistry Lab IFall 2008Fall 2008Dr. MilkevitchDr. MilkevitchOct 12 & 14, 2009Oct 12 & 14, 2009Separating MoleculesSeparating MoleculesTodayToday: Learn a separation technique: Learn a separation techniqueMolecules can be separated by a number of Molecules can be separated by a number of methods:methods:–ExtractionExtraction–PrecipitationPrecipitation–ChromatographyChromatographyChromatography = “to write in color”Chromatography = “to write in color”–Originally developed to separate components of inksOriginally developed to separate components of inksThin Layer ChromatographyThin Layer ChromatographyThin Layer ChromatographyThin Layer Chromatography:: “The separation of “The separation of moderately volatile or nonvolatile substances based upon moderately volatile or nonvolatile substances based upon differential adsorption on an inert solid (differential adsorption on an inert solid (stationary phasestationary phase) ) immersed in a organic solvent or solvent mixture (immersed in a organic solvent or solvent mixture (mobile mobile phasephase)”)”Makes use of:Makes use of:–A stationary phaseA stationary phase: solid support: solid support–Mobile phase:Mobile phase: a fluid a fluidBasic principle of separation:Basic principle of separation: Differential interactions of molecules with these 2 phasesDifferential interactions of molecules with these 2 phasesHow the separation worksHow the separation worksMolecules can move with the mobile phaseMolecules can move with the mobile phaseOr, they can remain fixed on the stationary Or, they can remain fixed on the stationary phasephaseCalled Called partitioningpartitioningHow molecules partition between the 2 How molecules partition between the 2 phases depends on:phases depends on:–Properties of the phasesProperties of the phases–Properties of the molecules being separatedProperties of the molecules being separatedHow this works, continued How this works, continued Molecules that partition into Molecules that partition into the mobile the mobile phase:phase:–Will move more rapidly than molecules that partition into Will move more rapidly than molecules that partition into the stationary phasethe stationary phase–Therefore, they will Therefore, they will separateseparate from those that are partitioned from those that are partitioned into the stationary phaseinto the stationary phaseTwo component mixtureapplied to TLC plateSlower moving componentpartitioned more into stationary phaseFaster moving componentpartitioned more into mobile phaseSolvent movement““Nuts and Bolts” of the MethodNuts and Bolts” of the MethodYou must carefully select mobile and stationary You must carefully select mobile and stationary phases to achieve full separation of mixtures of phases to achieve full separation of mixtures of moleculemolecule–Trial and errorTrial and errorStationary phase:Stationary phase: thin layer of silica spread on a thin layer of silica spread on a surfacesurfaceMobile phase:Mobile phase: solvent system that migrates through solvent system that migrates through the silicathe silicaSamples are spotted on the plateSamples are spotted on the plateMoved along by the solvent(s) migrating through the Moved along by the solvent(s) migrating through the silicasilicaRRff Values ValuesMolecules that are separated will migrate as “spots” and their Molecules that are separated will migrate as “spots” and their migration can be measuredmigration can be measuredMigration usually reported as an “RMigration usually reported as an “Rff” value” valueCalculation of an RCalculation of an Rff value: value:–Ratio of sample migration (how far spot moved) to solvent migration Ratio of sample migration (how far spot moved) to solvent migration (how far the solvent moved)(how far the solvent moved)Can be used to identify components in a mixture Can be used to identify components in a mixture –Compared to standardsCompared to standardsToday: look at the components of analgesic tablets by TLCToday: look at the components of analgesic tablets by TLC–Look for the “actives”Look for the “actives”Calculating an RCalculating an Rff Value ValueOriginSolvent FrontSpot 1 Spot 2Solvent Front = 5 cmSpot 1 moved 1 cm Rf = 1/5 = 0. 2 cmSpot 2 moved 4 cm Rf = 4/5 = 0. 8 cmAnalgesic MedicationsAnalgesic Medications““Analgesia”:Analgesia”: Greek Greek for the deadening or absence of pain for the deadening or absence of pain without loss of consciousnesswithout loss of consciousness–Analgesics: Analgesics: compounds that relieve paincompounds that relieve painRange from aspirin to morphine, and other related Range from aspirin to morphine, and other related narcoticsnarcoticsMany OTC (over the counter) analgesics availableMany OTC (over the counter) analgesics available–TylenolTylenol–AdvilAdvil–ExcedrinExcedrin–Aspirin (various preparations)Aspirin (various preparations)ActivesActivesOTC analgesics contain OTC analgesics contain many compoundsmany compoundsThe “active” is what The “active” is what relieves painrelieves painOther compounds are Other compounds are binders, flavorings, binders, flavorings, colorants, stabilizers, colorants, stabilizers, solubility enhancerssolubility enhancersOHNOParacetamol (acetaminophen)OHOIbuprofenNNNNOOCaffeineProcedureProcedureObtain a silica gel plate from meObtain a silica gel plate from me–This plate will have a UV indicator in itThis plate will have a UV indicator in itDraw a straight line (lightly, in pencil) approximately 2 cm from the bottom Draw a straight line (lightly, in pencil) approximately 2 cm from the bottom edge of your TLC plate. Use a ruler to do this. edge of your TLC plate. Use a ruler to do this. This is called the origin. This is called the origin. Draw a straight line (lightly, in pencil) about 1 cm from the top edge of your Draw a straight line (lightly,