NY/T 3598-2020Fosetyl-aluminium wettable powder (English PDF)

4.3 Identification test

4.3.1 Ion chromatography

This identification test can be carried out simultaneously with the determination of the mass fraction of fosetyl-aluminium. Under the same chromatographic operating conditions, the relative difference between the retention time of the main chromatographic peak in the specimen solution and the retention time of the ethyphosphonate chromatographic peak in the standard solution shall be within 1.5%.

4.3.2 Aluminum ion identification

Please refer to Annex B for qualitative identification of aluminum ions.

4.4 Determination of the mass fraction of fosetyl-aluminium

4.4.1 Method summary

The specimen is dissolved in mobile phase. Sodium carbonate and sodium bicarbonate solutions are used as mobile phases. Use anion chromatography column and conductivity detector to perform ion chromatography separation of ethyphosphonate in the specimen. Use the external standard method for quantification (chemical titration method can also be used to determine the mass fraction of aluminum triacetate. See

Annex C for details).

4.4.2 Reagents and solutions

Water: ultrapure.

Sodium carbonate: guaranteed pure.

Sodium bicarbonate: guaranteed pure.

Standard sample of fosetyl-aluminium: known mass fraction of fosetyl-aluminium,

omega>=97.0%.

4.4.3 Instruments

Ion chromatograph: equipped with conductivity detector and suppressor.

Integrator or electronic data acquisition system.

Chromatographic column: 250 mm × 4 mm (inner diameter) anion separation column (filled with polyvinylbenzene/ethylvinylbenzene/polyvinyl alcohol matrix, with alkyl quaternary ammonium or alkanol quaternary ammonium functional groups) and anion protection column; particle size is 6 µm (or an equivalent chromatographic column).

Weigh 0.05 g (accurate to 0. 0001 g) of fosetyl-aluminium standard sample into a 100 mL volumetric flask. Add 20 mL of water. Place in an ultrasonic cleaner and sonicate for 30 min. Cool to room temperature. Use mobile phase to dilute to volume. Shake well. Use a pipette to transfer 1 mL of the above solution into another 100 mL volumetric flask. Dilute to the graduation with mobile phase. Shake well. Filter.

4.4.5.2 Preparation of specimen solution

Weigh a specimen containing 0.05 g (accurate to 0.0001 g) of fosetyl-aluminium into a

100 mL volumetric flask. Add 20 mL of water. Place in an ultrasonic cleaner and sonicate for 30 min. Cool to room temperature. Dilute to the graduation with mobile phase. Shake well. Use a pipette to transfer 1 mL of the above solution into another 100 mL volumetric flask. Dilute to the graduation with mobile phase. Shake well. Filter.

4.4.5.3 Determination

Under the above operating conditions, after the instrument is stable, continuously inject several needles of the standard solution until the relative change in the peak area of two adjacent ethyphosphonate peaks is less than 1.5%. Measure in the order of standard sample solution, specimen solution, specimen solution, and standard sample solution.

4.4.5.4 Calculation

Average the ethosphonate peak areas in the measured two injections of sample solution and the two injections of standard solution before and after the specimen. The mass fraction of fosetyl-aluminium in the specimen is calculated according to formula (1).

Where,

omega1 - the mass fraction of fosetyl-aluminium in the specimen, in percent (%);

A2 - the average value of the ethyphosphonate peak area in the specimen solution;

m1 - the mass of the standard sample, in grams (g);

omega - the mass fraction of fosetyl-aluminium in the fosetyl-aluminium standard sample, in percent (%);

A1 - the average value of the ethyphosphonate peak area in the standard sample solution;

m2 - the mass of the specimen, in grams (g).

4.4.6 Allowable difference

The difference between the two parallel determination results of the mass fraction of fosetyl-aluminium shall be no more than 0.6% for 40% and no more than 1.0% for 80%.

Take the arithmetic mean as the measurement result.

4.5 Determination of phosphite

4.5.1 Method summary

The specimen is dissolved in mobile phase. Sodium carbonate and sodium bicarbonate solutions are used as mobile phases. Using an anion chromatography column and a conductivity detector, the phosphite in the specimen is separated by ion chromatography.

Conduct quantification by external standard method.

4.5.2 Reagents and solutions

Water: ultrapure.

Sodium carbonate: guaranteed pure.

Sodium bicarbonate: guaranteed pure.

Sodium phosphite pentahydrate standard: known mass fraction omega>=98.0%.

4.5.3 Instruments

Ion chromatograph: equipped with conductivity detector and suppressor.

Integrator or electronic data acquisition system.

Chromatographic column: 250 mm × 4 mm (inner diameter) anion separation column (filled with polyvinylbenzene/ethylvinylbenzene/polyvinyl alcohol matrix with alkyl quaternary ammonium or alkanol quaternary ammonium functional groups) and anion protection column; particle size is 6 µm (or an equivalent chromatographic column).

Filter: the pore size of the filter membrane is approximately 0.45 µm.

Microsampler: 50 µL.

Quantitative injection tube: 5 µL.

Ultrasonic cleaner.

4.5.4 Ion chromatography operating conditions

Mobile phase: carbonate eluent [c(Na2CO3) = 4.5 mmol/L + c (NaHCO3) = 0.8 mmol/L].

Weigh 477 mg of sodium carbonate and 67.2 mg of sodium bicarbonate and dissolve them in 1000 mL of water. Mix well.

Flow rate: 0. 8 mL/min.

4.6 Moisture

In accordance with the provisions of GB/T 1600.

4.7 pH

In accordance with the provisions of GB/T 1601.

4.8 Determination of suspension rate

Weigh a specimen containing 0.5 g of fosetyl-aluminium (accurate to 0.0001 g). Follow the provisions of 4.1 in GB/T 14825-2006. Use mobile phase to transfer the remaining

1/10 of the suspension to a 200 mL volumetric flask. Determine the mass fraction of fosetyl-aluminium according to 4.4. Calculate the suspension rate.

4.9 Determination of wetting time

Follow the provisions of GB/T 5451.

4.10 Wet screening test

Follow the provisions of 2.2 in GB/T 16150-1995.

4.11 Determination of persistent foaming properties

Follow the provisions of GB/T 28137.

4.12 Determination of thermal storage stability

Follow the provisions of 2.3 in GB/T 19136-2003. After thermal storage, the mass fraction of fosetyl-aluminium shall not be lower than 95% of that before storage. The pH, suspension rate, wetting time and wet screening test shall still meet the standard requirements to be qualified.

5.1 Acceptance

It shall comply with the provisions of GB/T 1604.

5.2 Quality assurance periods

Under the specified storage and transportation conditions, the quality assurance period for fosetyl-aluminium wettable powder is 2 years from the production date. During the quality assurance period, all indicators shall comply with standard requirements.

Annex B (informative)

Aluminum ion complex titration method

B.1 Principle

The determination of aluminum ions in fosetyl-aluminium samples adopts the complexometric titration method. That is, the fosetyl-aluminium sample is decomposed in an excess CDTA standard solution under acid and heating conditions; aluminum ions form a complex with CDTA; the excess CDTA standard solution is back-titrated with a zinc sulfate standard titration solution.

B.2 Reagents and solutions

Perchloric acid.

Xylenol orange.

Hexamethylenetetramine (HMTA).

1,2-Cyclohexanediaminetetraacetic acid (CDTA).

Sodium hydroxide.

Zinc sulfate standard titration solution: c(ZnSO4) = 0.05 mol/L.

Potassium nitrate.

Deionized water.

B.3 Instruments

150 mL beakers.

20 mL pipettes.

Automatic potentiometric titrator.

Magnetic stirrer with heating.

B.4 Operation steps

B.4.1 Preparation of CDTA standard solution

Weigh 8.5 g of sodium hydroxide into a 2 L volumetric flask. Add 500 mL of water to dissolve. Weigh out another 36.4 g of CDTA. Dissolve with heat. After cooling to room temperature, dilute to the graduation with water.

B.4.2 Preparation of perchloric acid solution

In a 500 mL beaker with 300 mL of water previously added, add 100 mL of perchloric acid while stirring.

B.4.3 Preparation of grinding indicator

Weigh 0.1 g of xylenol orange and 9.9 g of potassium nitrate and grind in a mortar until completely mixed.

B.4.4 Determination of blank CDTA standard solution

Use a pipette to transfer 20 mL of CDTA standard solution into a 250 mL Erlenmeyer flask. Add 20 mL of water to dilute. Add 5 mL of perchloric acid solution. Heat to boiling for about 1 min.

After cooling to room temperature, add 6.0 g of HMTA. Stir until completely dissolved.

Add 30 mg ~ 50 mg of grinding indicator. Titrate with zinc sulfate standard titration solution until the solution changes from yellow to red as the end point.

Repeat the determination three times.

B.4.5 Determination of sample

Weigh a specimen containing 0.1 g of fosetyl-aluminium (accurate to 0. 0001 g) into a

250 mL beaker. Add 20 mL of water. Add 5 mL of perchloric acid solution. Heat to boiling for about 1 min.

Add exactly 20 mL of CDTA standard solution. Heat to boiling for about 1 min. After cooling to room temperature, add 6.0 g of HMTA. Stir until completely dissolved. Add

30 mg ~50 mg of grinding indicator. Titrate with zinc sulfate standard titration solution until the solution changes from yellow to red as the end point.

B.5 Calculation of aluminum ions

The mass fraction of aluminum ions is calculated according to formula (B.1).

Where,

omega4 - the mass fraction of aluminum in the specimen, in percent (%);

V0 - the average value of the zinc sulfate standard titration solution volume consumed

Buffer solution: pH=7.3±0.2. Weigh 100 g of sodium hydroxide (accurate to 0. 0002 g) into a 2000 mL beaker. Add 1.8 L of water to dissolve. Neutralize to pH=8.0 with phosphoric acid solution. After cooling to room temperature, neutralize with phosphoric acid solution to pH=7.3±0.2. Add 30 g of potassium iodide and 20 mL of iodine standard titration solution. Stir to dissolve and transfer to a 2000 L volumetric flask.

Dilute to the graduation. Store in dark place at room temperature. Before use, titrate with sodium thiosulfate standard titration solution until colorless.

C.3 Instruments

Potentiometric titrator.

Ultrasonic water bath.

pH meter.

Adjustable heating mantle.

Spherical condenser tube.

Iodine vial: 250 mL.

Burette: 25 mL, brown.

C.4 Determination steps

C.4.1 Specimen solution

Weigh a specimen containing 3 g of fosetyl-aluminium (accurate to 0. 0001 g) and place it in a 500 mL volumetric flask. Add 200mL of sodium hydroxide B solution. Place the volumetric flask in an ultrasonic water bath and sonicate for 10 min. After cooling to room temperature, add sodium hydroxide A solution to the volume and mix well. Use a pipette to transfer 10 mL of the specimen solution into a 250 mL iodine flask. Add 40 mL of sodium hydroxide A solution. Connect to condenser pipe. Heat to boil and reflux for 1 h. Flush the condenser tube with a small amount of water. Cool to room temperature. Neutralize with sulfuric acid solution. Add 2 drops of phenolic acid indicator near the end point. Continue titration until the red color disappears.

C.4.2 Determination

Use a pipette to add 25 mL of buffer solution and 20 mL of iodine standard titration solution. Cap the bottle and mix well. Seal with water. Place the iodine bottle in a dark place for 30 min ~ 45 min. Add 3 mL of acetic acid to acidify. Titrate with sodium thiosulfate standard titration solution. Add 3 mL of starch indicator near the end point.

Continue titrating until the blue color of the solution disappears as the end point (or use a potentiometric titrator to determine the end point).

C.4.3 Blank determination

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