Gas chromatography problem solving and troubleshooting

The peaks are not column bleed. Column bleed is a continuous stream of stationary phase degradation products eluting from the column. Column bleed is a component of the baseline and not a series of peaks. Column bleed increases with temperature, especially at temperatures near the column’s upper temperature limit. When temperature programming up to the upper temperature limit, a rise in the baseline at higher temperatures is the typical and most obvious sign of column bleed. Most capillary column stationary phases are based on siloxane polymers. Although there are other types of stationary phases, polysiloxanes are definitely the most common. Polysiloxanes can be described as having a repeating silicon–oxygen backbone substituted with various side groups (i.e., methyl, phenyl, and cyanopropyl). At higher temperatures these very long chain polymers degrade into smaller lengths of the same repeating units that can elute from the column. These degradation products and their fragments comprise the mass spectra taken along the baseline (i.e., not on a peak). Silicones are used in a large number of common household and consumer products. They are found in large amounts in many soaps, lotions, deodorants, pharmaceuticals, and similar products. Silicones are also used in lubricants, protective coatings, sealants, Journal of Chromatographic Science, Vol. 39, July 2001