BS ISO 17780:2015 pdf download – Animal and vegetable fats and oils — Determination of aliphatic hydrocarbons in vegetable oils

BS ISO 17780:2015 pdf download – Animal and vegetable fats and oils — Determination of aliphatic hydrocarbons in vegetable oils 8 Preparation of the test sample Prepare the test sample in accordance with ISO 661. 9 Procedure 9.1 Chromatography column preparation 9.1.1 Preparation of AgNO 3 impregnated silica gel Preparation of the silver nitrate silica gel column (for 3 columns): weigh 45 g of silica gel (5.1) in a 500 ml round-bottomed flask (6.3) protected by aluminium foil. With a Pasteur pipette (6.12), add drop by drop the silver nitrate solution (5.12) shaking continuously. Shake well for 30 min to homogenize. After completing, cover the flask with aluminium foil and allow to stand at room temperature for 12 h before use. In order to improve homogenization, it is recommended to use an automatic shaker. If no automatic shaker is available, it is possible to put the flask in a rotatory evaporator equipment and rotate for 30 min without vacuum. NOTE 1 The impregnated silica gel can be stored one week at room temperature in a desiccator, provided the flask is protected with aluminium foil. NOTE 2 For screening purposes, AgNO 3 impregnated silica gel can be replaced by non-impregnated silica gel. The results will be similar or higher than those obtained using silvered silica gel. NOTE 3 For refined vegetable oils other than refined olive pomace oil, AgNO 3 impregnated silica gel can be replaced by non-impregnated silica gel. 9.1.2 Column packing In a beaker, suspend 18,5 g of silver nitrate impregnated silica gel (9.1.1) in n-hexane (5.4). The slurry is introduced onto the column (6.1) containing 40 ml of n-hexane and pack the column by tapping it gently using a glass rod (6.2). Add at least 0,5 cm to 1 cm of sodium sulfate (5.3) on top of the AgNO 3 – silica gel, and compress the AgNO 3 – silica gel bed with a stream of nitrogen. Rinse the AgNO 3 – silica gel with another 60 ml of n-hexane (5.4) to eliminate impurities in the AgNO 3 – silica gel. The column should be covered with a black paper cylinder or with aluminium foil to avoid oxidation of the silver nitrate. Elute the solvent until the level of the solvent in the column is about 0,5 cm higher than the AgNO 3 – silica gel bed. Put a 250 ml round-bottomed flask (6.3) under the chromatography column....