GB/T 24749-2020 in English

Gas chromatography (arbitration method)

Using HP-5 capillary column and dicyclohexyl phthalate as internal standard, the detection limit reaches 0.00001g, and the relative deviation is ≤1.2%. Typical chromatographic conditions:

• Column temperature: 210℃
• Carrier gas (N₂) flow rate: 2.0mL/min
• Retention time of propiconazole A: about 9.7min

Liquid chromatography

Use a C₈ column, methanol-water (65:35) mobile phase, and detection wavelength of 230nm. Compared with gas chromatography:

• Pretreatment is simpler
• Lower operating costs
• Suitable for routine quality control

Precautions for production enterprises

1. The moisture control process needs to be upgraded to ≤0.5% standard
2. The document system during the quality assurance period should include:
   • Raw material batch records
   • Production process parameters
   • Storage environment monitoring data
3. It is recommended to conduct infrared spectrum comparison every quarter

Operation specifications of testing agencies

When the difference between gas chromatography and liquid chromatography results is >1.2%, the gas chromatograph data shall prevail. Note on sample pretreatment:

• The weighing accuracy should reach 0.00001g
• The internal standard solution should be prepared and used immediately
• The crystalline sample should be completely dissolved

The evolution of this standard reflects the progress of my country's pesticide standard system:

• 2001 edition: The basic detection method was established for the first time
• 2009 edition: The quality control system was improved
• 2020 edition: In line with international standards, the following are added:
  • Methodology validation requirements
  • Measurement uncertainty assessment
  • Full supply chain traceability mechanism