If necessary, dry the sample with anhydrous sodium sulphate before extraction. Prevent adsorption of moisture from the air by storing the unused cartridges in sealed pouches or in a desiccator until just prior to use. Slow down the flow rate during sample application by adjusting the valve on the vacuum manifold or the cartage stopcock. Dissolve the sample in a different solvent, if possible. For example, if the isolate did not extract from hexane, try extracting it from chloroform.
Insufficient cleanup Interfering peaks or false positives appear during the analysis.
Wash the cartridge with a solvent that is not strong enough to elute the isolate. Evaluate different wash solvents or combinations thereof. Evaluate a different polar sorbent. The isolate should be soluble in the elution solvent. Increase solvent polarity.