Topics - Apiezon
Apiezon grease was first introduced as a gas chromatography (GC) high temperature stationary phase in the late 1950s. The early stationary phases that were used, such as squalane, dinonyl phthalate and the lower molecular weight polyethylene glycols had severe temperature limitations and could not be used much above 120C without significant column bleed. The apiezon greases were developed to have very low vapor pressures and, thus, be suitable for use in high-temperature high-vacuum work. Such materials were ideal for high temperature GC stationary phases. The apiezon materials were basically hydrocarbons of very high molecular weight which were extensively heated under high vacuum to remove the last remaining traces of lower molecular weigh materials. Apiezon greases are still used today for high temperature work but have been partly replaced by high molecular weight polyethylene glycols that can be used up to 225C. The carborane/silicones are, without doubt, the most temperature stable of all GC stationary phases. The weakly polar carborane/methyl phenyl silicone and the moderately polar carborane methyl cyanoethyl silicone can both be used at temperatures up to 400C. To date there are no strongly polar stationary phases that can be used at these temperatures.