Column Installation and Troubleshooting
Maintaining an oxygen and leak free system is the best prevention against oxygen damage. Good GC system maintenance includes periodic leak checks of the gas lines and regulators, regular septa changes, using high quality carrier gases, installing and changing oxygen traps, and changing gas cylinders before they are completely empty.
Chemical Damage
There are relatively few compounds that damage stationary phases. Introducing nonvolatile compounds (e.g., salts) in a column often degrades performance, but damage to the stationary phase does not occur. These residues can often be removed and performance returned by solvent rinsing the column.
Inorganic or mineral bases and acids are the primary compounds to avoid introducing into
a column. The acids include hydrochloric (HCl), sulfuric (H2S04), nitric (HNO3), phosphoric (H3PO4), and chromic (CrO3). The bases include potassium hydroxide (KOH), sodium hydroxide (NaOH), and ammonium hydroxide (NH4OH).Most of these acids and bases are not very volatile and accumulate at the front of the column. If allowed to remain, the acids or bases
damage the stationary phase. This results in the premature onset of excessive column bleed, peak tailing for active compounds and/or loss of efficiency (resolution). The symptoms are very similar to thermal and oxygen damage. Hydrochloric acid and ammonium hydroxide are the least harmful of the group. Both tend to follow any water that is present in the sample. If the
water is not or only poorly retained by the column, the residence time of the HCl and NH4OH in the column is short. This tends to eliminate or minimize any damage by these compounds. Thus,
if HCl or NH4OH are present in a sample, using conditions or a column with no water retention will render these compounds relatively harmless to the column.
The only organic compounds that have been reported to damage stationary phases are perfluoroacids. Examples include trifluoroacetic, pentafluoropropanoic, and heptafluorobutyric acid. They need to be present at high levels (e.g., 1% or higher). Most of the problems are experienced with splitless or Megabore direct injections where large volumes of the sample are deposited at the front of the column.
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