Solid Phase Extraction and Clean Up Column

Solid phase extraction is used in the analysis of compounds to get rid of interfering substances. These are dissolved or suspended in the mixture. SPE is also used to concentrate samples which otherwise are not detected because they are below the limit of detection of the instrument. The technique used in the purification of the analyte of interest depends on the affinity of the solute in the liquid or often called mobile phase for the stationary phase through which the sample passes through. For example a non-polar compound will have more affinity to a non-polar stationary phase than with the less polar mobile phase. Thus the compound of interest or the undesired impurity will be retained. Stationary phases can be made of silica gel beads with functional groups bonded to it. Non-polar columns will have probably a C18 hydrocarbon bonded to its surface. It can also be coated with antibodies which will attach specific antigens to it. Such columns are called immunoaffinity columns. Another stationary phase used by r-Biopharm to retain analyte of interest is by using a special molecular imprinted polymer. If the retained analyte is of interest then a second step is necessary to elute it out with another solvent. For trace concentration or enrichment of solutes at very low levels, large volumes of the mixture can be passed through the column and then eluted out with a suitable eluent.