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GB 5009.179-2016 English PDF (GB5009.179-2016)

GB 5009.179-2016 English PDF (GB5009.179-2016)

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GB 5009.179-2016: Determination of trimethylamine nitrogen in ham

This standard specifies methods for the determination of trimethylamine in aquatic animals and their products as well as meat and meat products. This standard applies to the determination of trimethylamine in aquatic animals and their products as well as meat and meat products.
GB 5009.179-2016
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
National food safety standard -
Determination of trimethylamine in food
ISSUED ON. AUGUST 31, 2016
IMPLEMENTED ON. MARCH 01, 2017
Issued by. National Health and Family Planning Commission of the PRC
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle ... 4
3 Reagents and materials ... 4
4 Instruments and equipment... 5
5 Analytical procedures ... 6
6 Expression of analytical results ... 8
7 Precision ... 8
8 Others ... 9
9 Principle ... 9
10 Reagents and materials ... 9
11 Instruments and equipment ... 10
12 Analytical procedures ... 10
13 Expression of analytical results ... 12
14 Precision ... 13
15 Others ... 13
Appendix A Chromatograms and mass spectrum ... 14
National food safety standard -
Determination of trimethylamine in food
1 Scope
This standard specifies methods for the determination of trimethylamine in aquatic animals and their products as well as meat and meat products.
This standard applies to the determination of trimethylamine in aquatic animals and their products as well as meat and meat products.
Method I - Headspace gas chromatography-mass
spectrometry
2 Principle
The specimen is extracted by the 5% trichloroacetic acid solution, the extract is placed in a sealed headspace bottle. The trimethylamine hydrochloride is converted to trimethylamine under the action of an alkali solution, it is equilibrated at 40 ??C for 40 min. Trimethylamine reaches the dynamic
equilibrium in both the gas and liquid phases. The gas in the headspace bottle is taken and injected into the gas chromatograph-mass spectrometer for testing. The retention time (RT), auxiliary qualitative ions (m/z 59 and m/z 42) and quantitative ions (m/z 58) are used for qualitative; the external standard method is used for quantitation.
3 Reagents and materials
Unless otherwise stated, the reagents used in this method are of analytical grade and the water is the grade I water as specified in GB/T 6682.
3.1 Reagents
3.1.1 Sodium hydroxide (NaOH).
3.1.2 Trichloroacetic acid (C2HCl3O2).
3.2 Preparation of reagent
3.2.1 50% sodium hydroxide solution. WEIGH 100 g of sodium hydroxide;
DISSOLVE it in 100 mL of water at 20 ??C ~ 30 ??C.
3.2.2 5% trichloroacetic acid solution. WEIGH 25 g of trichloroacetic acid; DISSOLVE it in water; MAKE its volume reach to 500 mL.
3.3 Standard substance
Trimethylamine hydrochloride (CAS. 593-81-7), molecular formula. (CH3)3NHCl, purity ??? 98%, which is placed in a desiccator and preserved at 4 ??C.
3.4 Preparation of standard solution
3.4.1 Trimethylamine standard stock solution. WEIGH 0.0162 g of
trimethylamine hydrochloride standard substance; USE the 5% trichloroacetic acid solution to dissolve and dilute it to 100 mL, which is equivalent to the trimethylamine standard stock solution of concentration 100 ??g/mL;
PRESERVE it at 4 ??C conditions.
3.4.2 Trimethylamine standard use solution. TAKE a certain volume of
trimethylamine standard stock solution; USE the 5% trichloroacetic acid solution to dilute it stepwise to the trimethylamine standard use solution which has a concentration of 1.0 ??g/mL, 2.0 ??g/mL, 5.0 ??g/mL, 10.0 ??g/mL, 20.0 ??g/mL, 40.0 ??g/mL, respectively.
4 Instruments and equipment
4.1 Gas chromatography-mass spectrometer. It is equipped with split/splitless sample injection inlet and electron impact ionization source (EI source). 4.2 Balance. The sensitivities are 0.1 mg and 1 mg, respectively.
4.3 Constant-temperature water bath. Temperature control accuracy is ?? 2 ??C. 4.4 Headspace bottle. The volume is 20 mL, equipped with Teflon silicone rubber pad and sealing cap, baked at 120 ??C for 2 h before use.
4.5 Micro-syringe. 1 mL.
4.6 Medical plastic syringe. 5 mL.
4.7 Homogenizer.
4.8 Meat grinder.
4.9 Low-speed centrifuge.
b) Carrier gas. high purity helium;
c) Flow rate 1.0 mL/min; inlet temperature 220 ??C;
d) Split ratio. 10.1;
e) Temperature-rise program. hold at 40 ??C for 3 min, increase to 220 ??C at the rate of 30 ??C/min, maintain for 1 min.
5.2.2 Mass spectrometry conditions
The mass spectrometry conditions are as follows.
a) Ion source. electron impact ionization source (EI source), temperature. 220 ??C;
b) Ionization energy. 70 eV;
c) Transmission line?€?s temperature. 230 ??C;
d) Solvent delay. 1.5 min;
e) Scanning mode. Selective ion monitoring (SIM).
5.3 Determination
5.3.1 Headspace sample injection. EQUILIBRATE the prepared specimen at
40 ??C for 40 min. Under the chromatographic mass spectrometry condition of 5.2, USE a syringe to extract 100 ??L of the gas above the solution in the headspace bottle; INJECT it into a GC-MS for determination.
5.3.2 Qualitative determination. USE the selective ion monitoring method to collect data; USE the retention time (RT) of trimethylamine in sample solution, auxiliary qualitative ions (m/z 59 and m/z 42), quantitative ions (m/z 58), the kurtosis ratio (Q) of the auxiliary qualitative ions to quantitative ions, to perform the comparative qualitativeness with the standard solution. The relative deviation between the kurtosis ratio (Q sample) of the auxiliary qualitative ion to the quantitative ion of trimethylamine in the sample solution and the kurtosis ratio (Q standard) of the auxiliary qualitative ion to the quantitative ion of trimethylamine in the standard solution is controlled within ??15%.
5.3.3 Quantitative determination. USE the external standard method for
quantification. USE the peak area of trimethylamine in the standard solution as the ordinate and the concentration of trimethylamine in the standard solution as the abscissa, DRAW the standard curve; USE the calibration curve to calculate the concentration of trimethylamine in the sample solution.
10.4.1 Trimethylamine standard stock solution. WEIGH 0.0162 g of
trimethylamine hydrochloride standard substance; USE the 5% trichloroacetic acid solution to dissolve and dilute it to 100 mL, which is equivalent to the trimethylamine standard stock solution of concentration 100 ??g/mL;
PRESERVE it at 4 ??C conditions.
10.4.2 Trimethylamine standard use solution. TAKE a certain volume of
trimethylamine standard stock solution; USE the 5% trichloroacetic acid solution to dilute it stepwise to the trimethylamine standard use solution which has a concentration of 1.0 ??g/mL, 2.0 ??g/mL, 5.0 ??g/mL, 10.0 ??g/mL, 20.0 ??g/mL, 40.0 ??g/mL, respectively.
11 Instruments and equipment
11.1 Gas chromatograph. It is equipped with split/splitless sample injection inlet and hydrogen flame ionization detector (FID).
11.2 Balance. The sensitivities are 0.1 mg and 1 mg, respectively.
11.3 Constant-temperature water bath. Temperature control accuracy is ?? 2 ??C. 11.4 Headspace bottle. The volume is 20 mL, equipped with Teflon silicone rubber pad and sealing cap, baked at 120 ??C for 2 h before use.
11.5 Micro-syringe. 1 mL.
11.6 Medical plastic syringe. 5 mL.
11.7 Homogenizer.
11.8 Meat grinder.
11.9 Low-speed centrifuge.
12 Analytical procedures
12.1 Preparation of specimen
12.1.1 Pretreatment and preservation of specimen
For livestock, poultry meat and meat products, REMOVE fat and skin. For animal aquatic products such as fish, shrimp and their products, it is necessary to descale or peel it. For all samples, TAKE about 100 g of muscle part; USE the meat grinder to crush it or the knife to cut it; MIX it uniformly. If the prepared specimen is not immediately determined, it shall be sealed in a polyethylene plastic bag and preserved frozen at -18 ??C. Before the determination, PLACE it i) Hydrogen?€?s flow rate. 40 mL/min;
j) Air?€?s flow rate. 400 mL/min.
12.3 Determination
12.3.1 Headspace sample injection. EQUILIBRATE the prepared specimen at 40 ??C for 40 min. Under the above chromatographic mass spectrometry
conditions, USE a syringe to extract 250 ??L of the gas above the solution in the headspace bottle; INJECT it into a GC-FID for determination.
12.3.2 Qualitative quantification. PERFORM the qualitative analysis based on the retention time of trimethylamine in the standard chromatogram. USE the external standard method for quantitative analysis. USE the standard peak area as the ordinate and the concentration of the standard solution as the abscissa, to draw the calibration curve. USE the calibration curve to calculate the concentration of trimethylamine in the sample solution.
13 Expression of analytical results
13.1 The content of trimethylamine in the specimen is calculated according to formula (3).
Where.
X3 - The content of trimethylamine in the specimen, in milligrams per
kilogram (mg/kg);
c - The concentration of trimethylamine obtained from the calibration curve, in milligrams per milliliter (mg/mL);
V - The constant volume of the sample solution, in milliliters (mL);
m - The mass of the specimen, in grams (g).
13.2 The content of trimethylamine nitrogen in the specimen is calculated according to formula (4).
Where.
X4 - The content of trimethylamine nitrogen in the specimen, in milligrams per kilogram (mg/kg);

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