Polyadipates used as plasticizers in food contact: fraction below 1000 Da determined by size exclusion chromatography...

Polyadipates might be a suitable replacement for conventional plasticizers in plastisols to produce lids for glass jars complying with legal limits for oily foods. For the characterization of polyadipates, the proportion of the material with a molecular mass below 1000 Da is important. Determination of the material < 1000 Da is also important for checking compliance with the specific legal limit. The analytical problems and the sources of uncertainty are investigated. Even when calibrated with constituents of polyadipates, preseparation at 1000 Da is of limited accuracy, since stretched and cyclic components of the same molecular mass have different retention times; a compromise must be found. UV detection leaves substantial uncertainty as the response particularly of the < 1000 Da components varies and tends to be below that of the higher molecular mass polyadipates. Evaporative light scattering detection has a nonlinear response for which a segmental correction (linearization of the integration raw data) is suggested: The raw data of the integration is linearized by an exponential function before the chromatogram is reconstructed.