Solid-Phase Extraction and Column Chromatography
The solvent extracts can be cleaned up by traditional column chroma tography  or by solid-phase extraction cartridges. This is a common cleanupmethod that is widely used in biological, clinical, and environmental samplepreparation. Some examplesinclude the cleanup of pesticid e residues and chlorinated hydrocar bon s, theseparation of nitrogen compounds from hydrocarbons, the separation ofaromatic compounds from an aliphatic–aromatic mixture, and similarapplicat ions for use with fats, oils, and waxes. This approach provides e‰-cient cleanup of steroids, esters, ketones, glycerides, alkaloids, and carbohydrates as well. Cations, anions, metals, and inorganic compounds are alsocandidates for this method.
The column is packed with the required amount of a sorbent and loadedwith the sample extract. Elution of the analytes is e¤ected with a suita blesolvent, leaving the interfering compounds on the column. The packingmat erial may be an inorganic substance such as Florisil (basic magnesium
silicate) or one of man y commercially available SPE stationary phases.    Thee luate may be further concentrated if necessary. A Florisil column is shownin Figure 1.1. Anhydrous sodium sulfate is used to dry the sample. These cleanup and concentration techniques may be used individually, orin various combinations, depending on the nature of the extract and theanalytical method used.

Figure 1.1.Column chromatography for sample cleanup.