Overview
ISO 7431-1:2024 - "Thiourea for industrial use - Part 1: Test methods" defines standardized laboratory test methods for assessing the quality and purity of industrial thiourea. The first edition specifies procedures to measure thiourea content, water‑insoluble matter, ignition residue, initial melting point, turbidity, thiocyanate content, calcium, and heavy metals. The standard also sets general requirements for reagents, water quality and sampling to support consistent, reproducible results.
Keywords: ISO 7431-1:2024, thiourea test methods, industrial thiourea, thiourea content determination, chemical quality control
Key topics
- Scope of tests: Quantitative methods for key quality attributes of industrial thiourea (content, impurities, residues, physical properties and trace elements).
- Analytical principles:
- Thiourea content by oxidation with iodine under alkaline conditions with excess iodine titrated using sodium thiosulfate (standard solutions described).
- Thiocyanate determination by liquid ion chromatography methods referenced to ISO 10304‑3.
- Calcium determination by ion chromatography, ICP‑OES, and AAS (atomic absorption spectrometry) as a referee method.
- Turbidity measurement referenced to ISO 7027‑1.
- General requirements: Use of analytical‑grade reagents, tertiary water per ISO 3696, and sample preparation and sampling according to ISO 8213 and ISO 3165.
- Test documentation: Apparatus lists, reagent formulations (e.g., iodine and sodium thiosulfate standard solutions), stepwise procedures, calculation methods and expression of results are provided to support laboratory QA/QC.
- Safety note: Thiourea is hazardous (toxic by ingestion and skin absorption and environmentally harmful); users must follow safety and regulatory requirements.
Applications
- Quality control in production: Chemical manufacturers and formulators use ISO 7431‑1 methods to verify thiourea purity and impurity limits before shipment or downstream processing.
- Incoming material inspection: Procurement and QC labs in pharmaceuticals, dyes, rubber accelerators, flotation agents and resin manufacturing rely on these test methods for supplier acceptance.
- Regulatory and compliance testing: Laboratories performing conformity assessment, safety data sheet validation and environmental monitoring use standardized methods for consistent reporting.
- Method selection: Laboratories can choose between ion chromatography, ICP‑OES or AAS for elemental analysis depending on equipment, detection limits and referee‑method requirements.
Related standards
Relevant referenced standards include: ISO 3165, ISO 3696, ISO 6353‑1, ISO 7027‑1, ISO 7980:1986, ISO 8213, ISO 10304‑3:1997, ISO 11885:2007, and ISO 14911:1998 - these cover sampling, reagent preparation, water quality, turbidity, and instrumental methods (ion chromatography, ICP‑OES, AAS).
