GB 5009.181-2016National food safety standard - Determination of malondialdehyde in food (English PDF)

3.1 Reagents

3.1.1 Methanol (CH3OH). chromatographically pure.

3.1.2 Trichloroacetic acid (C2HCl3O2).

3.1.3 Ethylene diamine tetraacetic acid (C10H14N2Na2O8 · 2H2O).

3.1.4 Thiobarbituric acid (TBA) (C4H4N2O2S).

3.2 Preparation of reagents

3.2.1 Ammonium acetate solution (0.01 mol/L). WEIGH 0.77 g of ammonium

acetate; ADD water to dissolve and dilute to 1000 mL; and USE a 0.45 µm filter to filter.

3.2.2 Trichloroacetic acid mixture. accurately WEIGH 37.50 g (accurate to 0.01

g) of trichloroacetic acid (3.1.2) and 0.50 g (accurate to 0.01 g) of ethylene diamine tetraacetic acid (3.1.3); USE water to dissolve, dilute to 500 mL.

3.2.3 Aqueous solution of thiobarbituric acid (TBA). accurately WEIGH 0.288 g

(accurate to 0.001 g) of thiobarbituric acid (3.1.4) dissolved in water and diluted to 100 mL (If not easy to dissolve, it can be heated by ultrasonic until completely dissolved. After cooling, DILUTE to volume of 100 mL), equivalent to 0.02 mol/L.

3.3 Standard

1,1,3,3-tetraethoxypropane (also known as malondialdehyde acetal, C11H24O4,

CAS number. 122-31-6). Purity>=97%.

3.4 Preparation of standard solutions

3.4.1 Standard stock solution of malondialdehyde (100 µg/mL). Accurately

TRANSFER 0.315 g (accurate to 0.001 g) of 1,1,3,3-tetraethoxypropane to a

1000 mL volumetric flask; after dissolving in water, DILUTE to 1000 mL; SET in a refrigerator at 4 °C for storage. It is valid for 3 months.

3.4.2 Standard use solution of malondialdehyde (1.00 µg/mL). accurately

PIPETTE 1.0 mL of standard stock solution of malondialdehyde (3.4.1); USE trichloroacetic acid mixture (3.2.2) to dilute to 100 mL; SET in a refrigerator at

4 °C for storage. It is valid for 2 weeks.

3.4.3 Standard series solution of malondialdehyde. accurately PIPETTE 0.10

mL, 0.50 mL, 1.0 mL, 1.5 mL, 2.5 mL of standard use solution of malondialdehyde in 10 mL volumetric flasks; ADD trichloroacetic acid mixture (3.2.2) to dilute to volume. The concentration of the series of standard solutions is 0.01 µg/mL, 0.05 µg/mL, 0.10 µg/mL, 0.15 µg/mL, 0.25 µg/mL. Prepared when used.

4.1 High performance liquid chromatography. equipped with a diode array

detector.

4.2 Balance. The sensitivity is 0.0001 g, 0.01 g.

4.3 Thermostatic oscillator.

4.4 Thermostatic water bath.

to the standard curve, the concentration of malondialdehyde in the solution to be tested is obtained. The liquid chromatogram of malondialdehyde standard is shown in Appendix A.

11.1 Sample preparation

WEIGH 5 g (accurate to 0.01 g) of the sample; PLACE it in a 100 mL conical flask with stopper; accurately ADD 50 mL of trichloroacetic acid mixture; SHAKE it well; and USE the stopper to seal. PLACE on a thermostatic oscillator to shake at 50 °C for 30 min; REMOVE, and COOL to room temperature. USE double-layer quantitative slow filter paper to filter; DISCARD the primary filtrate;

and the subsequent filtrate is standby.

Accurately PIPETTE 5 mL of the above filtrate and of standard series solution respectively; PLACE them in 25 mL colorimetric tube with stopper. TAKE another 5 mL of trichloroacetic acid mixture as a sample blank; ADD 5 mL of aqueous solution of thiobarbituric acid (TBA) respectively; COVER the stopper;

and MIX well. PLACE in a 90 °C water bath to react for 30 min; TAKE out; and

COOL to room temperature.

11.2 Determination

USE the sample blank to adjust the zero point. At 1 cm optical path at a wavelength of 532 nm, the absorbance of the sample solution and the standard series solution (9.4.3) is determined. USE the mass concentration of the standard series solution as the abscissa. USE the absorbance value as the ordinate. The standard curve is drawn.