Disposable Cartridge Extraction of Retinol and α-Tocopherol from Feedstuffs

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Abstract
Automated determination of fat-soluble vitamins by modern methods such as liquid chromatography is hampered by the initial extraction step. A simple technique is proposed that allows an appreciable increase in the actual rates of determination. Feedstuff samples are first hydrolyzed in an aqueous alcohol (mainly methanol)-potassium hydroxide solution. Instead of extracting retinol and a-tocopherol from the hydrolysis solution by an organic solvent, an aliquot of the solution is mixed with a small volume of a strong antioxidant solution (ascorbic acid) and pipetted onto a kieselguhr disposable cartridge where it is adsorbed. Retinol and a-tocopherol are eluted with isooctane at normal pressure. The proposed method has been compared with conventional techniques on many feed samples.