GB 5009.307-2025National food safety standard - Determination of formaldehyde in foods (English PDF)

3.1 Reagents

3.1.1 Glacial acetic acid (C2H4O2).

3.1.2 Acetylacetone (C5H8O2).

3.1.3 Ammonium acetate (C2H7O2N).

3.1.4 Phosphoric acid (H3PO4).

3.1.5 Dimethyl silicone oil.

3.2.1 Acetylacetone solution. Weigh

25.0 g of ammonium acetate and dissolve it in 90 mL of water; then add

0.4 mL of acetylacetone and

3.0 mL of glacial acetic acid; dilute to 100 mL with water; mix well; and transfer to a brown reagent bottle. Prepare immediately before use.

3.2.2 Phosphoric acid solution (200 g/L). Weigh 20 g of phosphoric acid; dilute to 100 mL with water; mix well; and store at room temperature.

3.3 Standard sample Formaldehyde (CH2O, CAS No.. 50-00-0) standard solution. 1,000 mg/L, or other standard samples certified by the state and awarded with standard substance certificates. NOTE. Formaldehyde standard solution can also be prepared and calibrated with 36% ~38% formaldehyde solution. For specific operations, see Appendix A.

3.4.1 Formaldehyde standard intermediate solution (100 mg/L). Accurately pipette

1.00 mL of 1,000 mg/L formaldehyde standard solution; dilute with water and make constant volume to 10 mL; prepare a formaldehyde standard intermediate solution with a mass concentration of 100 mg/L; store at 2 °C ~8 °C away from light; and the validity period is 3 months.

3.4.2 Formaldehyde standard working solution (

1.0 mg/L). Accurately pipette

1.0 mL of 100 mg/L formaldehyde standard intermediate solution; dilute with water and make constant volume to 100 mL; prepare a formaldehyde standard working solution with a mass concentration of

1.0 mg/L. Prepare immediately before use.

3.4.3 Formaldehyde series standard working solution. Accurately pipette 0 mL,

0.50 mL,

1.0 mg/L formaldehyde standard working solution into 25 mL stoppered colorimetric tubes; add water to make constant volume to 10 mL; and prepare formaldehyde series standard working solutions with mass concentrations of 0 mg/L,

0.050 mg/L,

0.10 mg/L,

0.20 mg/L,

0.40 mg/L,

0.80 mg/L and

1.0 mg/L, respectively. Prepare immediately before use.

5.2.1 Distillation Accurately pipette

25.00 mL of the specimen; place it in a 500 mL distillation flask; add 20 mL of phosphoric acid solution (200 g/L), 1 mL of dimethyl silicone oil, and 50 mL of water; and perform steam distillation. Pre-add 10 mL of water to a 250 mL receiving flask; insert the receiving tube below the liquid surface; and place it in an ice bath. When about 195 mL of distillate is collected; take it out. Place it at room temperature for 30 min; transfer it to a 200 mL volumetric flask; add water to the scale; shake it well and set aside.

5.2.2 Color development Accurately pipette

10.0 mL of the distillate prepared in

5.2.1 and place it in a 25 mL stoppered colorimetric tube. Add 1 mL of acetylacetone solution (3.2.1) to the stoppered colorimetric tube; cover the stopper; and mix well. Place the stoppered colorimetric tube in a boiling water bath for 5 min; take it out; and cool it to room temperature.

5.3 Blank test Except for not adding the specimen, all other procedures are carried out according to Procedure 5.2.

5.4 Drawing of standard curve According to the method of 5.2.2, treat the formaldehyde series standard working solution (3.4.3) and the specimen at the same time and in the same way. After cooling to room temperature, place it in a 1 cm colorimetric dish; adjust the zero point as per the zero point of the formaldehyde series standard working solution as a reference; and measure the absorbance value at 415 nm. Use the concentration of the series standard working solution as the horizontal axis and its absorbance value as the vertical axis to draw a standard curve.

5.5 Determination of specimen solution Place the solution obtained in

5.3 in a 1 cm colorimetric dish and measure the absorbance at 415 nm. If the sample result exceeds the standard linear range, dilute it with a blank specimen solution and then measure it again. NOTE. The obtained sample solution shall be measured within 1 h. ultraviolet detector.

11.2 Electronic balance. Sensitivity is 1 mg.

11.3 Constant temperature water bath oscillator. Controllable temperature at 25 °C ±1 °C, accuracy of 0.1 °C.

11.4 Vortex mixer.

11.5 Centrifuge. Speed >=4,000 r/min. 11.6 0.45 µm organic filter membrane.

12.2.1 Derivatization For wine samples, accurately pipette

5.00 mL of the specimen. For other samples, weigh 2 g of the prepared specimen (accurate to

0.01 g); place it in a 50 mL plastic centrifuge tube; accurately add 20 mL of the derivatization solution (10.2.3); cover the tube tightly; vortex to mix. Place in a constant temperature water bath oscillator; shake at 25 °C ± 1 °C for 1 h to allow it to react fully.

12.2.2 Extraction Immediately add 8 g of sodium chloride to the above test solution; vortex and mix for 30 s; centrifuge at no less than 4,000 r/min for 5 min; take the upper solution into a 20 mL volumetric flask. Add 10 mL of acetonitrile to the centrifuge tube; vortex and mix for 30 s; centrifuge at no less than 4,000 r/min for 5 min. Combine the upper solution; and make constant volume to the scale with acetonitrile; and mix well. Filter through a 0.45 µm organic filter membrane and provide for liquid chromatography determination.

12.3 Blank test Except for not adding the specimen, all other procedures are carried out according to Procedure 12.2.

12.4.1 Chromatographic column. C18 column (column length 250 mm, inner diameter

4.6 mm, particle size 5 µm); or chromatographic column with equivalent performance.

12.4.2 Mobile phase. acetonitrile-water (50.50, volume ratio).

12.4.3 Column temperature. 30 °C.

12.4.4 Detection wavelength. 350 nm.

12.4.5 Flow rate. 1 mL/min.

12.4.6 Injection volume. 20 µL.

12.5 Drawing of standard curve Accurately pipette 0 mL,

0.050 mL,

0.10 mL,

0.20 mL,

0.40 mL,

0.60 mL and

0.80 mL of 100 mg/L formaldehyde standard intermediate solution into 50 mL plastic centrifuge tubes respectively. According to the derivatization and extraction procedures in 12.2, obtain formaldehyde series standard working solutions with mass concentrations of 0 mg/L,

0.25 mg/L,