NY/T 1374-2007 Determination of fluorine in plant products Ion chromatography NY/T1374-2007 standard download decompression password: www.bzxz.net
This standard specifies the method for determining fluorine in plant products such as grains, vegetables, and fruits by ion chromatography. This standard is applicable to the determination of fluorine in plant products such as grains, vegetables, and fruits. The linear range of this method is 0.005mg/L～5mg/L. The detection limit of this method is 0.1mg/kg.

ICS67.050
Agricultural Industry Standard of the People's Republic of China
NY/T1374-2007
Determination of Fluorine in Plant Products
Ion Chromatography
Determination of Fluorine in Plant ProductsIon Chromatography Method
2007-06-14 Issued
2007-09-01 Implementation
Ministry of Agriculture of the People's Republic of China
1 Scope
Determination of Fluorine in Plant ProductsIon Chromatography This standard specifies the method for determining fluorine in plant products such as grains, vegetables, and fruits by ion chromatography. This standard is applicable to the determination of fluorine in plant products such as grains, vegetables, and fruits. The linear range of this method is 0.005mg/L~5mg/L. The detection limit of this method is 0.1mg/kg.
2 Principle
NY/T1374—2007
Use alkali to fix the fluorine in the sample, and convert it into salt form by high temperature ashing. Under neutral or weak alkaline conditions, use ion exchange chromatography-conductivity detector to determine, and use external standard method for quantification. 3 Reagents and materials
Unless otherwise specified, all reagents used are analytical grade, and the water used is deionized water with a conductivity of less than 1μS/cm. 3.1 Sodium fluoride (NaF): high-grade pure.
3.2 Potassium hydroxide (KOH) or sodium hydroxide (NaOH): high-grade pure, crushed before use. 3.3 Sulfuric acid solution [c(H2SO4)=50g/L]: Measure 30mL of sulfuric acid, slowly inject it into 1000mL of water, cool, and shake well. 3.4 Strong acid cation exchange resin (H type): Soak 732# strong acid cation exchange resin (total exchange capacity ≥ 4.2mmol/g) in water, wash 3 times with 5 volumes of water, wash with 1 volume of methanol, and then wash with 5 times and 10 times the volume of water several times until the washing water is colorless and clear, pour out the washing water as much as possible, add 2 volumes of sulfuric acid solution (3.3), stir with a glass rod for 1h to convert the resin to H type, then wash with water several times until the pH of the washing water is about 6, transfer the resin to a wide-mouth bottle and cover with water for later use. Note: Commercial H-type cation exchange resin columns can be used. 3.5 Chromatography column: 0.8cm (inner diameter) × 10cm (height) chromatography tube. 3.6 Fluorine standard stock solution (1000 mg/L): Accurately weigh 2.2101 g of sodium fluoride (3.1) that has been dried at 100°C ± 5°C for 4 hours and cooled to room temperature, dissolve in water, transfer to a 1000 mL volumetric flask, add water to the mark, and mix. Store in a polypropylene or high-density polyethylene bottle at 4°C. 3.7 Fluorine standard working solution (10 mg/L): Pipette 1.0 mL of fluorine standard preparation solution (3.6), place in a 100 mL volumetric flask, add water to the mark, and mix. Standard working solution should be prepared before use. 3.8 Fluorine standard working solution: Pipette 0 mL, 0.25 mL, 0.50 mL, 1.00 mL, 2.50 mL, 5.00 mL, and 10.00 mL of fluorine standard working solution (3.7) respectively, and dilute to 50 mL with water. Each corresponds to a fluorine concentration of 0 mg/L, 0.05 mg/L, 0.10 mg/L, 0.20 mg/L, 0.50 mg/L, 1.00 mg/L, and 2.00 mg/L. Standard working solutions should be prepared before use. 4 Instruments
4.1 Ion chromatograph: equipped with conductivity detector. 4.2 0.22 μm aqueous sample filter.
4.3 Nickel crucible: 50 mL.
4.4 High temperature electric furnace.
4.5 Balance: accuracy ±0.0001 g, ±0.001 g. 5 Sample preparation
5.1 Vegetables and fruits: Take the edible part, wash, dry, chop, mix, weigh 100g~200g sample, dry at 80℃, crush, pass through 1
NY/T1374—2007
0.15mm mesh sieve, mix. Determine the moisture content at the same time. 5.2 Grains and other plants: After removing visible impurities, take 50g~100g representative sample, dry at 80℃, crush, pass through 0.15mm mesh sieve, mix. Determine the moisture content at the same time.
6 Analysis steps
6.1 Sample decomposition
Weigh 0.5g~1g sample (accurate to 0.001g) and place it in a pot, add 1.0g±0.1g potassium hydroxide (or sodium hydroxide) solid (3.2) to make it evenly distributed, carbonize at low temperature for 30min, move it into a high-temperature electric furnace, ash it at 500℃ for 10min, take it out and cool it. Add 20mL of water to dissolve the sample, transfer this solution to a 100mL volumetric flask, wash the pot with 20mL of water several times, add it to the volumetric flask, dilute it to the scale with water, mix it well, and set aside. Slowly pour the H-type cation exchange resin (3.4) into the chromatography column (3.5) with the water outlet closed. Stir the resin with a glass rod to drive out bubbles and allow the resin to settle naturally. After the resin is loaded, open the water outlet, control the flow rate to 2mL/min, add 20mL of water to rinse, and after the water in the column flows out naturally, immediately add the prepared sample solution along the inner wall of the column, discard the first 3mL of effluent, collect the subsequent 2mL of effluent, filter it through a 0.22um filter, and then test it. 6.2 Determination
6.2.1 Instrument reference conditions
6.2.1.1 Chromatographic column: quaternary ammonium polystyrene resin, particle size 5um, 250mm×4mm (id) or equivalent. 6.2.1.2 Mobile phase: 3.2mmol/LNazCOg/1.0mmol/LNaHCO, filter it through a 0.45μum filter membrane before use, or select the mobile phase according to the different instruments.
6.2.1.3 Flow rate: 0.7mL/min.
6.2.1.4 Regeneration solution: 50mmol/LH2SO4g6.2.1.5 Detection cell temperature: room temperature.
6.2.2 Test solution determination
Take equal volumes of sample solution and standard working solution (3.8) for single-point or multi-point calibration, and quantify by the integral value of the chromatographic peak area. The fluoride ion response values ​​in the standard working solution and sample solution should be within the linear range of the instrument detection. 6.3 Blank test
Except for not adding the sample, the same determination steps are used for parallel operation. 7 Calculation of results
The fluorine content in the sample is expressed as mass fraction w, expressed in milligrams per kilogram (mg/kg), and is calculated according to formula (1): (C-Co) V
Wherein:
C is the mass concentration of the fluorine ion response value in the sample solution on the standard curve, in milligrams per liter (mg/L); Co is the mass concentration of the fluorine ion response value in the blank test on the standard curve, in milligrams per liter (mg/L); V is the total volume of the sample solution, in milliliters (mL); m is the mass of the sample, in grams (g). The calculation result shall retain two significant figures.
8 Precision
The absolute difference between two independent test results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean of the two measured values, provided that the difference is greater than 10% of the arithmetic mean of the two measured values ​​and does not exceed 5%. 2 wwW.bzxz.Net
The chromatogram of the fluorine standard substance is shown in Figure A.1.
1. Ammonium ion
Appendix A
(Informative Appendix)
Chromatogram of standard substance
Chromatogram of standard substance of oxygen ion
NY/T1374—2007
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