Meaning
Chromatography tubes coated with a stationary phase such as polydimethylsiloxane separate chemical species primarily by their boiling points. A non-polar capillary column is the standard choice for analyzing mineral oil saturated hydrocarbons in plastic packaging. This type of column provides excellent thermal stability and minimal interaction with the hydrocarbon molecules.
Stationary Phase
Thin films of non-polar material allow for the efficient separation of straight-chain and branched alkanes. Because the non-polar capillary column does not interact strongly with polar groups, it is less likely to suffer from peak tailing when analyzing non-polar contaminants. The thickness of the film determines the retention time and the sample capacity for a given inner diameter.
Retention Behavior
Analytes elute in an order that closely follows their vapor pressure at the oven temperature. In a non-polar capillary column, the separation of heavy waxes from lighter oils is predictable and repeatable across different laboratory runs. This predictability is necessary for the accurate identification of hydrocarbons based on their retention indices.
Thermal Stability
High-temperature operation is possible because the non-polar phases are resistant to chemical breakdown. A non-polar capillary column can often reach three hundred degrees Celsius without excessive signal noise, which is required for eluting high-molecular-weight species. This durability ensures a long service life and consistent performance in a production environment.
