Meaning
Saturated hydrocarbons containing one or more rings of carbon atoms belong to the naphthenic group of mineral oil constituents. These cycloalkanes are common in the base oils used to produce polymer additives and lubricants. Their presence is monitored in food contact materials because they can migrate into the contents.
Analytical chemists distinguish them from linear structures to assess the total saturated hydrocarbon content.
Ring Structure
Carbon atoms in these molecules form closed loops that provide more rigidity than open chains. Because cycloalkanes have higher boiling points than their acyclic counterparts, they behave differently during gas chromatography.
Separation Technique
Liquid chromatography separates these cyclic compounds from the aromatic fraction of a mineral oil sample. In the subsequent gas chromatography stage, cycloalkanes appear as a series of peaks or a humped baseline. This pattern results from the wide variety of possible ring sizes and substitutions.
Laboratories use flame ionization detection to quantify the total mass of the naphthenic fraction. Accurate identification ensures that the saturated hydrocarbon limit is not exceeded in the final plastic part.
Physical Property
Higher density and viscosity are typical for oils rich in these ringed molecules. The stability of cycloalkanes makes them resistant to chemical breakdown during the high heat of injection moulding. Manufacturers select resins with low concentrations of these compounds to avoid tainting sensitive food products.
