A new sensitive and selective method has been developed for the quantification of the total coenzyme Q9 (CoQ9) and coenzyme Q10 (CoQ10) concentration in vegetable oil samples. The coenzyme Q fraction is isolated by solid-phase extraction (SPE) on amino phase eluting with a mixture of heptane:ethyl ether. The organic solvent is evaporated under nitrogen, and the residue is dissolved in a mixture of acetonitrile:tetrahydrofuran and finally is analyzed by reverse-phase high-performance liquid chromatography with a mass detector. The sensitivity of the method is based on the high efficient formation of the radical anions [M (-.)] of CoQ9 and CoQ10 by negative atmospheric pressure ionization. Interferences are minimized by using mass detection of the [M (-.)] ions ( m/ z = 797.5 for CoQ9 and m/ z = 862.5 for CoQ10) in selective reaction monitoring mode ( m/ z = 797.5 --> m/ z = 779.5 and m/ z = 862.5 --> m/ z = 847.5) using a triple-quadrupole mass spectrometer. The method was successfully applied to sunflower, soybean, and rapeseed oils, with a limit of quantification of 0.025 mg/kg for both compounds.
The research of contaminants is part of multiple controls conducted by fat and oil industry to verify the conformity of products placed on the market in relation to regulations as for instance the commission regulation EC n o 1881/2006 setting maximum levels for some contaminants in food as lead, some mycotoxins, dioxins, polychlorobiphenyls, benzo [a]pyrene. In the absence of regulation, the detection of contaminants must be addressed in partnership with authorities according to the toxicity of molecules. The controls are not confined to environmental contaminants. They also include compounds that can be formed during the production process of vegetable oils such as esters of 3-monochloropropanediol. This article focuses on recent research analytical development more particularly on those related to polycyclic aromatic hydrocarbons, mineral oils, phthalates and esters of 3-monochloropropanediol.
Résumé : Afin d'améliorer la sensibilité et la répétabilité du dosage des traces d'hexane résiduel dans les corps gras pour des teneurs de l'ordre du mg/kg, une optimisation de la méthode décrite dans la norme Afnor NF T 60-257 a été entreprise en chromatographie en phase gazeuse. L'utilisation d'une colonne de type wide-bore à film épais, en couplage avec un appareil automatique d'espace de tête statique ou même en pratiquant l'analyse avec injection manuelle, permet de quantifier 0,25 mg/kg d'hexane technique. La linéarité de la réponse est très bonne dans le domaine de teneurs considéré, de 1 à 10 mg/kg. Les taux de récupération sont satisfaisants puisqu'ils sont compris entre 93 et 107 % pour les échantillons de concentration en hexane technique comprise entre 0,25 et 2 mg/kg. Les résultats témoignent également de la bonne répétabilité de cette méthode ; en effet, pour une concentration de 1 mg/kg, le coefficient de variation est d'environ 3 %. Mots-clés :huiles végétales raffinées, résidus, solvant d'extraction, hexane technique, chromatographie en phase gazeuse, espace de tête statique. Summary :In order to increase the sensitivity and repeatability of the determination of residual hexane content in fats and oils for levels of about 1 mg/kg, an optimization of the procedure given in the Afnor standard NF T 60-257 was realized. Using a wide-bore gas chromatography column, coupled with an automatic headspace apparatus or even operating in manual injection, allows to quantify 0.25 mg/kg of technical hexane. Linearity of the response is very good in the considered scale, 1 to 10 mg/kg. Recovery rates are satisfying, between 93 and 107% for samples with levels between 0.25 and 2 mg/kg of technical hexane. The improved method has also a good repeatability ; relative standard deviation is about 3% for a 1 mg/kg concentration.
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