The occurrence of mineral oil hydrocarbons (MOH) traces in food and especially in edible oils and fats has raised public concern [1]. Hydrocarbons of petrogenic origin are composed of varying ratios of saturated mineral oil hydrocarbons (MOSH) and aromatic mineral oil hydrocarbons (MOAH). The MOSH group consists of numerous mostly branched but also unbranched open-chain hydrocarbons, also named paraffins, and of cycloalkanes with varying alkylation patterns, the so-called naphthenes [2,3]. MOAH comprise aromatic hydrocarbons with one or more aromatic ring systems which are nearly exclusively alkylated [2,4]. MOH sources of relevance include depending on the food matrix printing inks released from recycled packaging, as well as lubricating oils and greases [5], [6], [7], [8], [9] either used as processing aids or present as general background contamination in the environment [10]. In cases, the determination of the respective contamination origin may pose a challenge [10]. MOH tend to accumulate in the human body [5], [6], [7] and the MOAH fraction is suspected to display toxicity [11]. Currently, there are no legal limits for MOH in foodstuff but recommendations have been issued by the European Food Safety Agency and the German Federal Institute for risk assessment (BfR) to minimise mineral oil residues in foods [6,8] and the Standing Committee on Plants, Animals, Food and Feed (SCoPAFF) of the European Commission [12]. The SCoPAFF recommendations are expected to be adopted as official regulation. MOH quantification is meanwhile done routinely using automated liquid chromatography-gas chromatography-flame ionisation detection (LC-GC-FID) procedures including integrated sample preparation for the epoxidation of interfering natural olefins and aluminium oxide treatment for the removal of biogenic n-alkanes, enabling high sample-throughput at reduced contamination risk [13]. Standardisation and improvement of sample preparation are currently ongoing [14,15,16,17].

MOSH and MOAH are typically separated by LC on a normal phase and then either transferred consecutively onto the same short (10 –15 m) GC column with a thin film (0.1-0.25 µm) via on-column-type interfacing [2,10,18,19,20] or separately onto two similar column configurations. Accordingly, either one or two flame ionisation detectors are employed. Though a number of alternative LC-GC interfacing concepts involving programmed temperature vaporising (PTV) have been described [21], commercial laboratories apply exclusively the standardised procedure according to EN 16995 [14] and ISO/DIS 20122 [15]. While some workers in the field use hydrogen as carrier gas [13,17] as suggested by EN 16995 [14] and that is considered superior due to the higher gas velocity in the precolumn [13], others, including some routine laboratories use helium [10,16,22], especially if FID is used in parallel to MS detection [23]. Instead, nitrogen is generally considered as a poor carrier gas. According to the van Deemter equation nitrogen has a low optimum of linear velocity which tends to increase the run time for sufficient separations and apparently has never been considered as carrier gas for LC-GC-FID analysis of MOSH/MOAH traces in the literature. Cost benefit considerations triggered the quest for a investigation of nitrogen as alternative to the usual carrier gases for the LC-GC-FID quantification of MOSH and MOAH with sufficient accuracy and sensitivity. For this purpose, neat mineral oils, (highly refined mineral oil, gear oil, engine oil with significant amounts of MOAH, two coconut oils and two infant formula samples each displaying MOSH/MOAH trace concentrations of practical relevance were employed. GC parameters were optimised for each carrier gas and the separation and quantification characteristics were compared and are discussed in regard to practical implications.