Rapid Multidimensional Liquid–Gas Chromatography for the Analysis of Saturated Hydrocarbon Contamination in Foods containing Vegetable Oil

Jan 01, 2012
Volume 25, Issue 1

This article describes a rapid heart-cutting liquid chromatography–gas chromatography (LC–GC) method for the analysis of mineral oil saturated hydrocarbons (MOSHs) found in a range of widely-consumed foods, including crisps, margarine, tinned tuna and vegetable oils.

The automated LC–GC experiments were performed using a system equipped with a syringe-type interface capable of both heart-cutting and comprehensive two-dimensional analysis. The first dimension separation was achieved on a silica column operated under isocratic conditions using hexane. The heart-cuts were then transferred to a programmed temperature vaporizer. After the large volume injection (LVI), the target analytes were rapidly separated (~ 9 min) using a micro-bore GC capillary column. The overall LC–GC run time enabled the analysis of around four samples in an hour. Various degrees of MOSH contamination — ranging from "not detected" to around 390 mg/kg — were discovered in the thirty samples that were subjected to analysis.

The contamination of foods with mineral oil saturated hydrocarbons (MOSHs) is an important issue. Mineral oil is derived from crude oil and mainly consists of MOSHs and mineral oil aromatic hydrocarbons (MOAHs). MOSHs are formed of straight and branched alkanes, as well as cyclic constituents such as naphthenes (1). Many papers based on this specific type of contamination have been reported over the last two decades. Grob et al. for example, reported various sources for this type of contamination, including mineral batching oil used for spinning jute, as well as lubricating oils and release agents used in the food industry (2,3). Printing inks that use mineral paraffins as solvents were found to have contamination levels between 10–100 mg/kg in foods contained in cardboard boxes (4). A case of mineral oil contamination in meats and eggs, caused by animal feed containing fat from waste collection sites, has also been reported (5). Another source of contamination is from the atmosphere. Neukom et al. investigated the presence of C20–C50 MOSHs in particulate matter from polluted air and suggested that this was an important source of MOSH contamination in vegetable oils (6).

In general, the presence of MOSHs in vegetable oils has been well-documented (6–9): Fiselier and Grob analysed sunflower oils using LC–GC analysis and discovered MOSH contamination levels between 2.7–32 mg/kg (7). It was suggested in this study that, apart from the atmosphere, contamination was also related to harvesting, storage, transport and processing. Two-hundred and twenty vegetable oil samples were analysed by Wagner et al., with levels of MOSH reaching 80 mg/kg (8). Recently, Tranchida et al. analysed several commercial vegetable oils and found some high levels of MOSH contamination, particularly for a pomace oil sample (9).

The use of food grade (white) mineral oil that contains only saturated hydrocarbons and no aromatics is allowed in the food industry.

The Joint FAO/WHO Expert Committee on Food Additives (JECFA) published a list of admissible daily intake (ADI) values for white mineral oils (10): for a high viscosity white oil the highest ADI value suggested was 20 mg/kg, while the lowest was 0.01 mg/kg for a low viscosity product. Recently, the European Food Safety Authority (ESFA) suggested an ADI value of 12 mg/kg bw (body weight)/day for high viscosity white mineral oils (11).

At the moment there are no legal concentration limits for MOSHs in foods, except for one specification defined by the EU Commission (50 mg/kg) for Ukrainian sunflower oil, following a critical case of contamination (12). What is known is that MOSHs are probably the most abundant contaminants in the human body, with the intake starting from the first day of our lives (13). Furthermore, the exact toxicological effects of such a high and constant exposure to MOSHs is still not known (14).

From an analytical perspective, heart-cutting LC–GC with a flame ionization detector (FID) is a suitable method for the determination of MOSHs in foods. Recently, Tranchida et al. developed a rapid, sensitive LC–GC method for the analysis of MOSHs in a selection of vegetable oils (9). The current research is based on the use of the fast LC–GC to analyse vegetable oils, as well as other commonly consumed foods, such as crisps, margarine and tinned tuna. Various degrees of contamination were found in the samples chosen.

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