Eluent backflush

The additive fraction was collected using either a simple elution technique or eluent backflush. The final determinations were performed by GC with flame ionization detection and GC with MS. 

In addition, column-switching between three columns coupled together for sample cleanup, concentration of analyte, and analytical separation proved to be a rugged, automated means of isolating dexamethasone from bovine tissues (528). The analyte, along with co-eluting matrix components, was heart-cut from the first, phenyl-silica, column and collected on a second, silica, column. The second column was then backflushed with a stronger eluent onto the third, cyanopropyl-silica, column where the analyte was finally resolved from matrix components. 

Because of differences in swelling, columns are converted to the appropriate metal form in the bulk form before packing the column. Samples containing salts (cations) should be desalted to prevent displacement and precipitation of the metal from the column. If a metal gets displaced by other metals that may be in the sample or eluent, it is sometimes possible to regenerate the column with salt. For example, CaEDTA can sometimes be used to regenerate a Ca-form column. This regeneration should be done in the backflush mode. 

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