GB 5009.306-2025National food safety standard - Determination of diphenyl ether in foods (English PDF)

3.1 Reagents

3.1.1 n-hexane (C6H14). Chromatographically pure.

3.1.2 Sodium chloride (NaCl).

3.1.3 Anhydrous magnesium sulfate (MgSO4).

3.1.4 Sodium citrate (C6H5Na3O7).

3.1.5 Disodium hydrogen citrate (C6H6Na2O7).

3.2 Standard sample Diphenyl ether (Phenyl ether, C12H10O, CAS No.. 101-84-8). Standard substance purity >= 99%; or standard sample certified by the state and awarded with a standard substance certificate.

3.3 Preparation of standard solutions

3.3.1 Diphenyl ether standard stock solution (1,000 mg/L). Accurately weigh 10 mg (accurate to

0.1 mg) of diphenyl ether standard sample; dissolve it in n-hexane and make constant volume to 10 mL; store at 4 °C in the dark; the validity period is 3 months; or directly purchase a standard solution that meets the traceability requirements.

3.3.2 Diphenyl ether standard intermediate solution (

10.0 mg/L). Accurately pipette

0.25 mL of diphenyl ether standard stock solution into a 25 mL volumetric flask; and make constant volume with n-hexane. Store at 4 °C away from light; with a validity period of 1 week.

3.3.3 Standard working solution. Accurately pipette

0.50 mL,

10.00 mL of diphenyl ether standard intermediate solution; make constant volume to 10 mL with n-hexane; and prepare standard working solutions with mass concentrations of 0.5 µg/mL, 1.0 µg/mL, 2.0 µg/mL, 5.0 µg/mL and 10.0 µg/mL, respectively. Prepare immediately before use.

3.4 Materials

3.4.1 N-propylethylenediamine (PSA) solid phase adsorbent. Particle size 40 µm~60 µm.

3.4.2 Graphitized carbon black (GCB) solid phase adsorbent. Particle size 120 µm~400 µm.

5.2.1 Fruits and fruit and vegetable juices. Weigh 5 g of the specimen (accurate to

0.001

g) in a 50 mL centrifuge tube; add 10 mL of n-hexane; and vortex and oscillate for 1 min.

5.2.2 Fruit products, soft candy. Weigh 5 g of the specimen (accurate to

0.001

g) into a 50 mL centrifuge tube; add 10 mL of warm water at about 50°C; dissolve by ultrasonic for 30 min; accurately add 10 mL of n-hexane; and vortex for 1 min.

5.3 Salting out Respectively weigh 1 g of sodium chloride, 4 g of anhydrous magnesium sulfate, 1 g of sodium citrate, and

0.5 g of disodium hydrogen citrate in a n-hexane-water mixed solution; vortex and mix for 1 min; stand and cool to room temperature. Centrifuge at 5,000 r/min for 5 min; and wait for purification. NOTE. Commercial salt packs with the same adsorbent can also be used directly.

5.4 Purification Transfer 5 mL of the upper-layer n-hexane extract to a centrifuge tube containing 885 mg of anhydrous magnesium sulfate, 150 mg of N-propylethylenediamine (PSA) solid phase adsorbent, and 15 mg of graphitized carbon black (GCB) solid phase adsorbent; vortex and mix for 1 min; centrifuge at 5,000 r/min for 5 min; and take about 1 mL of the upper-layer clear liquid for determination. NOTE. Commercial salt packs with the same adsorbent can also be used directly.

5.5 Instrument reference conditions

5.5.1 Gas chromatography reference conditions The gas chromatography reference conditions are as follows:

a) Chromatographic column. 5% phenyl-methyl polysiloxane non-polar column [30 m×

0.32 mm (inner diameter), 0.25 µm (film thickness)], or equivalent;

b) Chromatographic column temperature. Maintain 80 °C for 1 min; increase to 150 °C at a heating rate of 10 °C/min, maintain for 10 min; increase to 280 °C at a heating rate of 30 °C/min, maintain for 1 min;

c) Inlet temperature. 285 °C;

d) Carrier gas flow rate.

e) Combustion gas. hydrogen, flow rate of about 30 mL/min;

f) Combustion-supporting gas. air, flow rate of about 300 mL/min; Method-II Gas Chromatography-Mass Spectrometry

10.3 Preparation of standard solutions

10.3.1 The same as 3.3.1.

10.3.2 The same as 3.3.2.

10.3.3 Standard working solution. Accurately pipette

0.025 mL,

0.050 mL,

0.100 mL,

0.200 mL and

0.500 mL of diphenyl ether standard intermediate solution; make constant volume to 10 mL with n-hexane; and prepare standard working solutions with mass concentrations of 0.025 µg/mL, 0.050 µg/mL, 0.100 µg/mL, 0.200 µg/mL and 0.500 µg/mL, respectively. Prepare immediately before use.

10.4 Materials The same as 3.4.

12.5 Instrument reference conditions

12.5.1 Gas chromatography-mass spectrometry reference conditions The gas chromatography-mass spectrometry reference conditions are as follows:

a) Chromatographic column. 5% diphenyl-methyl polysiloxane non-polar column [30 m×

0.25 mm (inner diameter) 0.25 µm (film thickness)], or equivalent;

b) Chromatographic column temperature. Maintain 80 °C for 1 min; increase to 150 °C at a heating rate of 10 °C/min, maintain for 10 min; increase to 280 °C at a heating rate of 30 °C/min, maintain for 1 min;

c) Inlet temperature. 285 °C;

d) Chromatography-mass spectrometry interface temperature. 280 °C;

e) Ion source temperature. 250 °C;

f) Carrier gas. Helium, Purity >= 99.999%, flow rate

g) Injection volume. 1 µL;

h) Injection method. Splitless injection, valve opening after