During the analysis, use only reagents of a purity of at least 98 %. Water of at least grade 3 as defined by ISO 3696 should be used.
Reference chemicals should be stored cold (at 4 o C), away from light, in aluminium containers or in tinted (amber) glass reagent bottles. The stoppers should preferably be fitted with an aluminium seal. Trans-anethole will need to be ‘thawed’ from its crystalline state before use, but in this case its temperature should never exceed 35 o C.
Add 560 g of distilled water to 378 g of ethanol 96 % vol.
All standard solutions should be stored at room temperature (15 to 35 o C) away from light in aluminium containers or in tinted (amber) glass reagent bottles. The stopper should preferably be fitted with an aluminium seal.
Trans-anethole and 4-allylanisole are practically insoluble in water, and it is therefore necessary to dissolve the trans-anethole and 4-allylanisole in some 96 % ethanol (4.1) before the addition of 45 % ethanol (4.4).
The stock solutions must be freshly prepared each week.
Stock solution of trans-anethole (concentration: 2 g/l)
Weigh 40 mg of trans-anethole (4.2) in a 20 ml volumetric flask (or 400 mg in 200 ml, etc.). Add some 96 % ethanol (4.1) and make up to volume with 45 % vol. ethanol (4.4), mix thoroughly.
Stock solution of internal standard, e.g. estragole (concentration: 2 g/l)
Weigh 40 mg of estragole (4.3) in a 20 ml volumetric flask (400 mg in 200 ml etc.). Add some 96 % vol. ethanol (4.1) make up to volume with 45 % vol. ethanol (4.4), mix thoroughly.
The linearity response of the FID must be checked for the analysis taking into account a range of concentrations of trans-anethole in spirits from 0 g/l up to 2.5 g/l. In the procedure of analysis, the unknown samples of spirits to be analysed are diluted 10 times (8.3). For the conditions of the analysis described in the method, stock solutions corresponding to concentrations of 0, 0,05, 0,1, 0,15, 0,2, and 0,25 g/l of trans-anethole in the sample to be analysed are prepared as follows: take 0,5, 1, 1,5, 2, and 2,5 ml of stock solution A (4.5.1) and pipette in separate 20 ml volumetric flasks; pipette into each flask 2 ml of internal standard solution B (4.5.2) and make up to volume with 45 % vol. ethanol (4.4), mix thoroughly.
The blank solutions (8.4) is used as the 0 g/l solution.
Take 2 ml of standard solution A (4.5.1) and pipette into a 20 ml volumetric flask, then add 2 ml of internal standard solution B (4.5.2) and make up to volume with 45 % vol. ethanol (4.4), mix thoroughly.]