Quantification and characterization of mineral oil in fish feed by liquid chromatography-gas chromatography-flame ionization detector and liquid chromatography-comprehensive multidimensional gas chromatography-time-of-flight mass spectrometer/flame ionization detector.

Mineral oil is an ubiquitous food contaminant potentially toxic. It is generally divided into aromatic hydrocarbons (MOAH) and saturated hydrocarbons (MOSH). These compounds are currently under investigation by the European Union to determine their occurrence and their toxicity before legislating on the matter. Although the discussion mainly focuses on food, animal feed can indirectly contribute to human exposure to such a contaminant. In this study, seven commercial feeds were analyzed. The analyses were carried out in two different Universities (Udine-IT and Liège-BE), performing the same sample preparation protocol: microwave-assisted saponification and extraction followed by epoxidation for the MOAH fraction. The final determination was performed by hyphenated liquid-gas chromatography (LC-GC) and LC coupled to comprehensive multidimensional gas chromatography (LC-GC × GC) with parallel detection, namely flame ionization detector (FID) and time-of-flight mass spectrometer (ToFMS). The results obtained by the two laboratories were generally in good agreement. The results obtained by LC-GC × GC-ToFMS/FID platform provided consistent results, with the advantages of more robust data interpretation that can compensate for problems occurring during purification. Moreover, the coupling of enhanced separation obtained by GC × GC and the MS information allowed for a more in-depth characterization of the contamination.

Evolution of hyphenated techniques for mineral oil analysis in food.

The occurrence of mineral oil in food is known since the early 1990s, and it was discovered by chance in one of the first applications using the hyphenated LC-GC system. Since then, the relationship between hyphenated techniques and mineral oil analysis has been tightly interrelated and successful. This review aims to show and explain how this mutual interaction has driven the development of the hyphenated techniques on one side and has supported the increase of knowledge on the other, supporting the complex task of mineral oil determination in food. The paper presents the background of the mineral oil problem in food (a brief history of its finding, toxicology, and occurrence), moving then toward the analytical determination. The development of different hyphenated techniques in relation to mineral oil determination is discussed, focusing mainly on 2D techniques, such as LC-GC. The necessity of additional dimensions, such as LC-LC-GC and comprehensive approaches, such as GC × GC and LC × GC, is also discussed. Finally, the role of the hyphenation with MS is presented.

A cotton thread fluidic device with a wall-jet pencil-drawn paper based dual electrode detector.

A simple and sensitive device is presented based on the use of pencil-drawn paper based electrochemical detector placed at the end of a cotton thread fluidic channel in wall-jet configuration. This innovative and fast responding electroanalytical system can be adopted for both single and dual electrode electrochemical detection, this last achieved by applying two different potentials at two independent working electrodes drawn on the opposite faces of the paper based detector. Its performance was preliminarily optimized by adopting hexacyanoferrate(II) as probe species undergoing reversible electrochemical processes. These devices were then used for the single electrode detection of ascorbic acid in aqueous samples and the dual electrode detection of orthodiphenols in extra virgin olive oils (EVOOs). In fact, these devices enable hydrophilic orthodiphenols, typically present in EVOOs (extracted by a 80:20% v/v acetonitrile/water mixture), to be discriminated from hydrophilic monophenols instead present in almost all vegetable oils. Flow-injections runs were conducted by using a 0.01 M H2SO4 + 0.5 KCl running electrolyte allowing the rapid and selective detection of hydrophilic orthodiphenols with satisfactory sensitivity and a low enough detection limit (2 µM). Different real samples of EVOOs and sunflower oils were analyzed. Abundant enough contents of orthidiphenols were found in EVOO samples, while no trace of these antioxidants was found in sunflower oils.