Preparative TREF and Size Exclusion Characterization of Olefin Oligomers
Preparative TREF combined with high-temperature SEC isolates and quantifies migrating sub-1000 Da polyolefin oligomers to verify food contact safety compliance.
Linear Alkanes
Meaning
Straight-chain saturated hydrocarbons consisting exclusively of carbon and hydrogen atoms connected by single bonds constitute linear alkanes. These molecules frequently occur as oligomeric byproducts in polyolefins and serve as reference markers in chromatographic analysis.
Chemical Properties
Polymerization of ethylene under specific catalytic conditions can yield low molecular weight fractions alongside the high polymer chains. These linear alkanes are highly non-polar, which makes them highly soluble in polyolefin matrices but poorly soluble in polar media. Their chemical stability is high because they lack reactive functional groups or double bonds, meaning they do not easily undergo further reactions during typical compounding temperatures.
Chromatographic Calibration
Gas chromatography utilizes a homologous series of these compounds to calculate retention indices for unknown extractables. By measuring the retention times of known linear alkanes, analysts can normalize chromatographic data across different systems and columns. This standardization is critical for the reproducible identification of polymer additives and migration compounds in food contact testing.
Moulding Performance
The presence of low molecular weight paraffinic species can significantly alter the processing and surface characteristics of a moulded part. During injection moulding, linear alkanes of low molecular weight can migrate to the surface of the part, acting as an unintentional external lubricant or causing surface defects such as haziness. In polymer sourcing, controlling the concentration of these oligomers is necessary to prevent finish defects and to ensure that the material complies with migration limits for food-contact applications.
Non Target Screening Workflows for Polyolefin Food Contact Oligomers
Non-target screening of polyolefin food contact oligomers requires dual GC-APCI and LC-HRMS analysis to resolve saturated aliphatic species below 1000 Da.