Capillary liquid chromatography combined with pressurized liquid extraction and dispersive liquid–liquid microextraction for the determination of vitamin E in cosmetic products

•Capillary LC uses both injected sample and mobile phase flow-rate very low.•Pressurized liquid extraction is proposed for the pretreatment of cosmetic products.•DLLME is useful for the preconcentration of tocopherols and tocotrienols.•The procedure is useful for routine control of vitamin E in cosmetic products.

Capillary liquid chromatography (LC) is used for the determination of tocopherols and tocotrienols in cosmetic products. Dispersive liquid–liquid microextraction (DLLME) allows the analytes to be preconcentrated into a very small volume of organic solvent which is then injected into the chromatograph running at a very low flow rate. Pressurized liquid extraction (PLE) at a high temperature and pressure was used to isolate vitamin E forms from cosmetics. The Taguchi experimental method was used to optimize the factors affecting DLLME. The parameters selected were 2 mL of acetonitrile (disperser solvent), 100 μL carbon tetrachloride (extraction solvent) and 10 mL aqueous solution. A volume of 5 μL of the organic phase was injected into the reversed-phase capillary LC system equipped with a diode array detector and using an isocratic mobile phase composed of an 95:5 (v/v) methanol:water mixture at a flow-rate of 20 μL min−1. Quantification was carried out using aqueous standards and detection limits were in the range 0.1–0.5 ng mL−1, corresponding to 3–15 ng g−1 in the cosmetic sample. The recoveries were in the 87–105% range, with RSDs lower than 7.8%. The method was validated according to international guidelines and using a certified reference material.

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