Migration of lubricants from food packagings: Screening for lipid classes and quantitative estimation using normal-phase liquid chromatographic separation with evaporative light scattering detection

A normal-phase high-performance liquid chromatography (NP-HPLC) method is introduced for the identification and quantitative estimation of 12 lipid classes (paraffin, wax esters, cholesterol esters, fatty acid methyl esters, triacyl glycerols, fatty alcohols, free fatty acids, cholesterol, 1,3-diacyl glycerols, 1,2-diacyl glycerols, monoacyl glycerols and fatty acid amide) used as lubricantsin food packaging materials. The HPLC separation is carried out on a LiChrospher® Diol (100 Å, 5 μm, 125 mm×3 mm) column with gradient elution (isooctane/0.1% acetic acid in tert-butyl methyl ether) and evaporative light scattering detection (ELSD). The method has been calibrated with representatives of each class in working ranges of about 5–150 mg/l, depending on the lipid class. Intra-day variance for all representatives range from 1.9 to 5.1%, inter-day variances from 7.0 to 26.5% and the limits of detection from 0.79 to 3.65 mg/l (except for two classes). A simple sample preparation could be established for the determination of migrating lubricants obtained from packaging materials containing external or internal lubricants. Since the detector response depends on the chain length and the degree of saturation, the quantification of a lipid class with unknown composition is only semi-quantitative. The amount of migrating lubricants from an epoxy-based can coating could be estimated with 0.3 mg/dm2 and from a light weight container with 5.5 mg/dm2.