Title: (empty line)
Author: Herr Dr. Amoneit
Last saved by: Gürbüzoglu, Meltem
Company: BUCHI Labortechnik AG

Automated Solid Phase Extraction for Sample Enrichment, Purification and Fractionation of Mineral Hydrocarbons from Vegetable Oils
S. Moret^1, P. Mattara^1, L.S. Conte^1, M. Sander^2
^1University of Udine, Department of Food Science, Via Sondrio 2A, 33100 Udine, Italy; ^2BÜCHI Labortechnik AG, Meierseggstrasse 40, 9230 Flawil, Switzerland

Mineral oils are widespread environmental and processing contaminants of petrogenic origin which can contaminate vegetable oils. Chemically, they are complex mixtures of saturated and aromatic hydrocarbons (1-4ring mainly alkylated compounds) that give gas chromatograms characterized by the presence of humps of unresolved peaks. Sample preparation before GC analysis must aim to separate the hydrocarbons from the bulk of the fat (and other possible interferences) and to pre-separate MOSH (mineral oil saturated hydrocarbons) and MOAH (mineral oil aromatic hydrocarbons), which have different toxicological relevance. Silica gel, silver silica and alumina sorbents are generally used for this purpose.
Online LC-GC provides a suitable method for low level analysis of mineral oils in different foods, but in the case of vegetable oils, due to the limited capacity of the LC column, it doesn’t reach the low quantification limits, without a previous enrichment step. A derivatisation step (epoxidation), which must be carefully optimised, is often required to eliminate interference by alkenes that are naturally present in the sample or originate from oil refining. SPE, carried out on small cartridges, suffers of the same drawbacks, while larger packed columns consume large amounts of solvent.
The aim of this work was to explore the potential of automated SPE (carried out on medium-size packed beds) for: (a) sample enrichment before on-line LC-GC-FID or direct large volume injection onto a GC-FID, (b) purification of the MOSH fraction from endogenous n-alkanes, (c) purification of the MOAH fraction from interfering alkenes, (d) MOAH separation according to ring number. Different sorbent and sorbent mixtures were tested to achieve these goals using a BUCHI SpeedExtractor E-916 equipped with six 10mL cells filled with the desired sorbents and eluted with different solvents/solvent mixtures. The results obtained demonstrated that automated SPE, if properly optimised, allows us to achieve all the goals obtaining sample enrichment (5-10fold concentration factor) with limited solvent consumption.