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This standard replaces GB/T 5009.181-2003 Determination of Propyldialdehyde in Lard.
The following main changes have been made with respect to GB/T 5009.181-2003 (the previous edition):
——This standard is renamed as National Food Safety Standard - Determination of Propyldialdehyde in Foods;
——The spectrophotometry in the former standard is reserved as Method II and application scope of the method is extended;
——High performance liquid chromatography is added as Method I and application scope of the method is extended;
——Annex A is added.
National Food Safety Standard
Determination of Propyldialdehyde in Foods
1 Scope
This standard specifies the determination method of propyldialdehyde in foods.
For the purposes of this standard, Method I is applicable to the determination of propyldialdehyde in foods and Method II is applicable to the determination of propyldialdehyde in animal and vegetable fats and oils.
Method I High Performance Liquid Chromatography
2 Principle
Extract the specimen with acid solution, then the extract and thiobarbituric acid react to generate colored compound, determine by high performance liquid chromatography - diode array detector and carry out quantitative determination by external standard method.
3 Reagents and Materials
Unless otherwise specified, analytically-pure reagents and Class-I water (defined in GB/T 6682) are adopted for the purpose of this method.
3.1 Reagents
3.1.1 Methanol (CH3OH): chromatographically pure.
3.1.2 Trichloroacetic acid (C2HCl3O2).
3.1.3 Ethylenediamine tetraacetic acid disodium (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 ammonium acetate, dissolve it with water, scale the volume to 1,000 mL and filter with 0.45 μm filter.
3.2.2 Trichloroacetic acid solution: accurately weigh 37.50 g (accurate to 0.01 g) trichloroacetic acid (3.1.2) and 0.50 g (accurate to 0.01 g) ethylenediamine tetraacetic acid disodium (3.1.3), dissolve in water and dilute to 500 mL.
3.2.3 Thiobarbituric acid (TBA) solution: accurately weigh 0.288 g (accurate to 0.001 g) thiobarbituric acid (3.1.4), dissolve in water and dilute to 100 mL (if it is not easy to dissolve, carry out ultrasonic heating till complete dissolution and scale the volume to 100 mL after cooling), equivalent to 0.02 mol/L.
3.3 Standard product
1,1,3,3-tetraethoxypropane (C11H24O4, CAS No.: 122-31-6): purity ≥ 97%.
3.4 Preparation of standard solutions
3.4.1 Propyldialdehyde standard stock solution (100 μg/mL): accurately transfer 0.315 g (accurate to 0.001 g) 1,1,3,3-tetraethoxypropane to a 1,000 mL volumetric flask, dissolve in water, dilute to 1000 mL and store in a 4℃ refrigerator. This solution is valid for 3 months.
3.4.2 Propyldialdehyde standard working solution (1.00 μg/mL): accurately transfer 1.0 mL propyldialdehyde standard stock solution (3.4.1), dilute with trichloroacetic acid solution (3.2.2) to 100 mL, and store in a 4℃ refrigerator. This solution is valid for 2 weeks.
3.4.3 Propyldialdehyde standard series solution: accurately transfer 0.10 mL, 0.50 mL, 1.0 mL, 1.5 mL and 2.5 mL propyldialdehyde standard working solutions into 10 mL volumetric flasks respectively, add trichloroacetic acid solution (3.2.2), scale the volume to the scale to obtain solution with the concentrations of 0.01 μg/mL, 0.05 μg/mL, 0.10 μg/mL, 0.15 μg/mL and 0.25 μg/mL and prepare immediately prior to use.
4 Instruments and Apparatus
4.1 High performance liquid chromatography: equipped with diode array detector.
4.2 Balance: with sensibility of 0.0001 g and 0.01 g.
4.3 Thermostatic oscillator.
4.4 Thermostat water bath.
4.5 Water-phase pin-type filter, with 0.45 μm polyether sulfone filter membrane.
5 Analysis Steps
5.1 Preparation of specimens
5.1.1 Extraction
Weigh 5 g (accurate to 0.01 g) uniform sample, put into a 100 mL conical flask with plug, accurately add 50 mL trichloroacetic acid solution, shake well, place the plug and seal it, place on the thermostatic oscillator to shake at 50℃ for 30min, take out, cool to ambient temperature, filter with double-layer quantitative slow filter paper, discard the primary filtrate and preserve the subsequent filtrate for standby use.
5.1.2 Derivatization
Accurately transfer 5 mL filtrate in 5.1.1 and standard series solution respectively, put them into 25 mL colorimetric tubes with stopper, add 5 mL thiobarbituric acid (TBA) solution, place the plug, mix uniformly, put into the 90℃ water bath to react for 30 min, take out, cool to ambient temperature, take proper amount of supernatant, filter with the filter membrane and put on the machine for analysis.
5.2 Reference conditions of liquid chromatography
Chromatographic column: C18 column, with length of 150 mm, inside diameter of 4.6 mm, particle size of 5 μm, or the one with equivalent performances.
Mobile phase: 0.01 mol/L ammonium acetate: methanol=70: 30 (volume ratio).
Column temperature: 30℃.
Flow rate: 1.0 mL/min.
Injection volume: 10 μL.
Detection wavelength: 532 nm.
5.3 Determination
Pipet standard series working solution (3.4.3) and derivative solution of to-be-determined specimen respectively, inject them into high-performance liquid chromatograph, determine corresponding peak area, plot the standard curve with the concentration of standard working solution as x-axis and the peak area response as y-axis, obtain the concentration of the propyldialdehyde in the to-be-determined solution from the standard curve, see Annex A for the liquid chromatogram of propyldialdehyde standard product.
6 Expression of Analysis Results
The propyldialdehyde content in the specimen is calculated according to Formula (1):
(1)
Where,
X——the propyldialdehyde content in the specimen, mg/kg;
c——the concentration of propyldialdehyde in specimen solution obtained from standard series curve, μg/mL;
V——the constant volume of specimen solution, mL;
m——the mass of specimen represented by the final specimen solution, g;
1000——the conversion coefficient.
The calculation result is expressed by the arithmetic average of the results from two independent determinations under repeatability condition, accurate to two significant figures.
7 Accuracy
The absolute difference of the results from two independent determinations under repeatability condition shall not exceed 10% of their arithmetic average.
Foreword i
1 Scope
2 Principle
3 Reagents and Materials
4 Instruments and Apparatus
5 Analysis Steps
6 Expression of Analysis Results
7 Accuracy
8 Principle
9 Reagents and Materials
10 Instruments and Apparatus
11 Analysis Steps
12 Expression of Analysis Results
13 Accuracy
14 Other
