GB 23200.16-2016Food safety national standard -- Determination of ethephon residues in fruits and vegetables -- Liquid chromatographic method (English PDF)

Foreword

This standard replaces NY/T 1016-2006 "Determination of ethephon residues in vegetables by gas chromatography".

This standard and GB/T 5009.7-2008 compared to the main changes are as follows.

- modified in accordance with the format of food safety standards;

- normative reference documents to increase the GB 2763 "maximum pesticide residues in food" standard;

- the preparation of the sample to increase the sampling site requirements and refine the requirements of the preparation of the sample;

- Increased precision requirements.

National standards for food safety Determination of ethephon residues in fruits and vegetables - Gas chromatographic method

1 Scope

This standard specifies the determination of ethephon residues in fruits and vegetables.

This standard is applicable to the analysis of ethephon residues in fruits and vegetables.

2 Normative reference documents

The following documents are indispensable for the application of this document. For dated filing applications, only the dated edition applies to this document.

For undated references, the latest edition (including all modifications) applies to this document.

GB 2763 National Standard for Food Safety - Maximum Residue Limit of Pesticides in Foodstuffs GB/T 6682 Analytical laboratory water specifications and test methods

3 Principle

Extraction of ethephon from the sample with methanol and derivatization of dimethylethylenediethanoxide by diazomethane with a flame photometric detector (phosphor filter) the gas chromatograph was determined by external standard method.

4 Reagents and materials

Unless otherwise stated, only chromatographic pure reagents are used in the analysis, and water is the primary water specified in GB/T 6682.

5 Instruments

5.1 gas chromatograph and equipped with flame photometric detector.

5.2 Ultrasonic cleaner.

5.3 Tissue crusher.

5.4 nitrogen dryers.

6 Analysis steps

7 Results calculated

The residual amount of ethephon in the sample is calculated using a chromatographic data processor or according to formula (1) 1000rho xxx xxxx VmA VVA .. (1) where.

The residual amount of ethephon in the sample, in milligrams per kilogram (mg/kg);

A chromatographic area of dimethylacetylene in sample solution;

The peak area of dimethyl vinyl chloride in As - standard solution;

The mass concentration of ethephon in the standard solution, in micrograms per milliliter (µg/mL);

V-extraction solvent volume, in milliliters (mL);

V1 - fractional volume in milliliters (mL);

V2 - on the machine volume, in milliliters (mL);

M-Weigh the quality of the sample in grams.

The calculated results shall be deducted from the blank values and the calculated results shall be the arithmetic mean of the two independent determinations obtained under reproducible conditions Show that two valid digits are reserved.

8 Precision

The ratio of the absolute difference between the two independent determinations obtained under reproducibility and its arithmetic mean (percentage) shall be in accordance with the Record B requirements.

The ratio of the absolute difference between the two independent determinations obtained under reproducibility and its arithmetic mean (percentage) shall be in accordance with the Record C requirements.

9 Limit of quantification

The limit of quantification for this standard method is 0.03 mg/kg.

10 Chromatogram Reference

The chromatogram of ethephon at a concentration of 0.05 mg/L is shown in Fig.

Appendix A

(Normative appendix) Diazomethane Preparation of A1 2 - nitroso - 2 - methylurea in a 250 mL flask, add 13.5 g of methylamine hydrochloride, add 67 g of water, add 40.2 g of urine, slowly reflux for 2 h 45 min After vigorous reflux for 15 min, cooled to room temperature, 20.2 g of sodium nitrite was added and the solution was cooled to 0 ° C. 80 g of ice was added to a 1 L beaker, and cooled in an ice-salt bath, then 13.3 g of sulfuric acid was added and the methylurea-nitrite was just added with stirring so that the temperature did not exceed 0 ° C, about 1 h plus finished. Nitrosomethylurea into a crystalline foam floating on top, immediately by suction filtration and well dry, and then A small amount of ice water washing, the resulting crystal into a vacuum dryer drying, the temperature does not exceed 4 °C.

Preparation of A2 Diazomethane in a 500 mL round bottom flask, 60 mL of 50% sodium hydroxide solution and.200 mL of ether were placed and the mixture was cooled to 0 ° C and then shaken and 20.6 g of 2-nitrous acid-2-methylurea was added thereto, and the flask was charged with a condenser tube for distillation. The lower end of the condenser pipe is connected with a receiving pipe, Through a double-hole rubber stopper immersed in a 250 mL Erlenmeyer flask in 40 mL of ether, the conical flask was placed in an ice-salt bath to cool and release the resulting gas was passed through a second 40 mL of diethyl ether, which was similarly cooled to below 0 ° C, and the reaction flask was placed on a water bath at 50 ° C the boiling point of the ether, and shake from time to time, the distilled ether until the distillate color becomes colorless, usually 2/3 of the ether after distilling off Becomes colorless. The ether can not be evaporated in any case and the ether solution in the receiver is combined with 5.3 g to 5.9 g of diazomethane.

Appendix B

(Normative appendix) Laboratory repeatability requirements

Table B.1 Laboratory repeatability requirements

Measured component content Mg/kg Precision <=0.001 36 > 0.01 > 1 14 Appendix C (Normative appendix) Inter-laboratory reproducibility requirements

Table C.1 Inter-laboratory reproducibility requirements

Measured component content Mg/kg Precision <=0.001 54 > 0.01 > 1 19