GB 5009.264-2016Determination of benzyl acetate in tea-drink -- Gas chromatography method (English PDF)

3.1 Reagents

3.1.1 Dichloromethane (CH2Cl2).

3.1.2 Anhydrous ethanol (C2H6O).

3.2 Standard substance

3.2.1 Benzyl acetate (C9H10O2). Content >= 98%.

3.2.2 n-Dodecane [CH3(CH2)10CH3]. Content >= 98%.

3.3 Preparation of standard solution

3.3.1 Benzyl acetate standard stock solution (1000 µg/mL). Accurately WEIGH

100 mg (accurate to 0.1 mg) of benzyl acetate; USE absolute ethanol to dissolve and dilute it to 100 mL.

3.3.2 Benzyl acetate use solution (80 µg/mL). Accurately TAKE 8.00 mL of 1000

µg/mL benzyl acetate solution; USE dichloromethane to make its volume reach to 100 mL. PREPARE it before use.

3.3.3 n-Dodecane internal standard solution (200 µg/mL). Accurately WEIGH

20 mg (accurate to 0.1 mg) of n-dodecane; USE dichloromethane to dilute it to

100 mL.

3.3.4 Preparation of mixed standard solution. ADD 4 mL of 80 µg/mL benzyl

acetate and 1 mL of 200 µg/mL n-dodecane solution into a 5 mL colorimetric tube; MIX it uniformly; it is used to calculate the relative correction factor.

5.1 Pretreatment of sample

Accurately WEIGH 40 g (accurate to 0.01 g) of tea-drink in a 125 mL separatory funnel; ADD 20 mL of dichloromethane; SHAKE it for 1 min; LET it be standing for layering; DROP the dichloromethane layer slowly into the funnel (a little cotton wool at the bottom, 10 g anhydrous sodium sulfate above it) to perform dehydration and filtration; COLLECT it into a 50 mL graduated test tube; then

ADD 20 mL of dichloromethane into the separatory funnel; SHAKE it for 1 min;

LET it be standing for layering; PERFORM filtration and collection as above;

then USE a small amount of dichloromethane to rinse the funnel for 3 times;

COLLECT it. USE nitrogen blow dryer (30 °C) to concentrate the collected solution to about 3 mL; USE a small amount of dichloromethane to completely transfer it into a 5 mL colorimetric tube. After adding 1 mL of 200 µg/mL n- dodecane, USE the dichloromethane to make its volume reach to 5 mL; MIX it uniformly to prepare for determination.

5.2 Reference conditions for gas chromatography

5.2.1 Chromatography column. SE-30 column, the column length is 30 m, the inner diameter is 0.53 mm, the film thickness is 1.0 µm, or others of equivalent performance.

5.2.2 Column temperature. The initial temperature is 90 °C. It is maintained at constant temperature 1 min, then subjected to programmed temperature-rise at the rate of 10 °C/min, the final temperature is 180 °C, which is kept for 3 min.

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