Direct analysis of aromatic hydrocarbons in purified mineral oils for foods and cosmetics applications using gas chromatography with vacuum ultraviolet detection

Highly purified mineral oils are used in several pharmaceutical, foods and cosmetics applications. A fast and simple method was developed for the analysis of the total level of residual mineral oil aromatic hydrocarbons (MOAH) in these oils and in the intermediate oils that were sampled during the purification process. The method is based on gas chromatography with vacuum ultraviolet detection (GC-VUV) and relies on the spectral differences between the aliphatic and aromatic compounds in the sample. Because the detector provides a good selectivity for aromatics, direct quantification of the MOAH content is possible without the need for a laborious preseparation of the mineral oil. The method was successfully applied for the direct analysis of the MOAH levels of 18 different mineral oil samples. The aromatics contents obtained by GC-VUV were similar to those obtained using two conventional methods (NPLC-GC-FID and SPE-GC-FID), with no statistically significant difference. The detector response was linear over the concentration range tested (0.5–20 mg/mL) and the repeatability (RSD value) was less than 8%, which is better than the typical values for the conventional methods (up to 15% RSD). The minimum MOAH level that can be determined with this method is approximately 0.13%, making the GC-VUV method sufficiently sensitive for the analysis of all but the highest purity mineral oils.