General methods as long as flash chromatography using disposable columns Flash chromatography Problems Chromatography theory Chromatography theory

General methods as long as flash chromatography using disposable columns Flash chromatography Problems Chromatography theory Chromatography theory www.phwiki.com

General methods as long as flash chromatography using disposable columns Flash chromatography Problems Chromatography theory Chromatography theory

Goldberg, Gail, Contributing Writer has reference to this Academic Journal, PHwiki organized this Journal General methods as long as flash chromatography using disposable columnsSpecial reportMarlon Vincent V. DuroMcK group meetingJuly 6, 2015How I went from this to this!Mol. Divers. 2009, 13, 247-252

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Flash chromatography“Rapid chromatographic technique as long as preparative separations with moderate resolution” (J. Org. Chem. 1978, 43, 2923-2925)Ubiquitous technique within organic chemistryAutomated pumps using disposable columns available among different br in addition to s (Teledyne Isco, Biotage, Silicycle, Yamazen)ProblemsQuestions about flow rates in addition to use of gradientsHow much silica to useHow fast of flow rateIsocratic, Stepwise or linear gradientDuring translation from TLC to flash chrom.Pre-existing guidelines not translated well among technologiesResulting in enormous waste of silica in addition to solvent ( in addition to more importantly, time!)Chromatography theoryTenetsIncreasing quantities of analyte reduces resolutionThere exists an optimal flow rate based on silica quality in addition to column geometryMore homogeneous phases pack better – give better resolutionStationary phases with smaller particles af as long as d better resolutionFlash chrom. is not expected to match the per as long as mance of HPLC but the equations can be adapted as long as optimizing the flow rate as long as a given column.

Chromatography theoryOptimized flow ratesFor normal-phase disposable flash columns (Teledyne Isco RediSep™ Rf 40-60 micron)Solvent system choice

Solvent system choiceOptimization is achieved using multiple analytical TLCs with different ratios of solvents.To achieve appropriate value of Rf (optimal retention) with appropriate CV ( optimal selectivity)Figures adapted from Teledyne Isco, Inc.Sample loadingLiquid loadingMinimize use of polar solvent (THF, acetone, DCM)For CV = 2 in addition to appropriate Rf, sample loading 1:20 (sample:silica)Chase with 1-2 CVs of initial mobile phase.Empty solid loading Silica gel, Celite, cotton (even boiling chips in addition to Kimwipes!)Use 2 to 10-fold excess by mass, recommended 1:40 silica(sample):silica(column)Place into solid load cartridgePre-packed solid loadingLoad as a liquid on the cartridge in addition to dry by suctionSample loadingFor difficult separations, it is better to use Gold columns (20-40 micron spherical particles, column has greater N)

Isocratic elutionFor two components, a TLC system that af as long as s CV >2 is appropriate as long as translation to isocratic elutionRf = 0.1, the Rf values must be between 0.1 in addition to 0.3Rf = 0.2, the Rf values must be between 0.1 in addition to 0.45If Rf = 0.5 as long as upper spot in addition to Rf = 0.1 with a mobile phase with X% strong solvent, try using a solvent with X/5 to X/2.Gradient elutionLinear gradients offer better resolution while reducing solvent waste.Samples are likely to be eluted in a state of higher purity.Linear gradient program from Biotage: when analytes show CV >2 with Rf values between 0.1 in addition to 0.5 in a system with X% strong solventSet initial condition as X/4 (or pure weak solvent if X/4 approached zero)Was column with 1-2 CV of initial mixtureRun a linear gradient of 10 CV from X/4 to 2XHold 2X solvent as long as 1 CV.Isco’s gradient optimizer toolUtilizing an isocratic “hold” which optimizes the slope of the gradient to maintain resolutionA shallower gradient increases separation with the trade-off of b in addition to broadening.

Case studyReaction:Rf 0.1 but CV < 2 -> Difficult separation~100 mg material, used 12G columnLiquid loading (in 0.5 mL DCM)targetimpurityPeakTrak’s Gradient OptimizerTake TLC’s in addition to input data

gradientisocratic holdResultsShould have used 24G columnAnother separation technique (SPE) was used to remove amine impurity

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