1. Verify Quality Management System (QMS) Certifications and Documentation

• Core Certifications: Prioritize suppliers with internationally recognized QMS certifications, such as ISO 9001 (general quality management) or industry-specific certifications (e.g., ISO 13485 for electronic-grade chemicals, FAMI-QS for food-grade inorganic salts). Confirm the certification is not expired and covers the specific inorganic chemicals you purchase (some certifications may only apply to a subset of the supplier’s products).
• System Documentation: Request the supplier to provide key QMS documents, including:
  • Raw material inspection standards (e.g., how they test the purity of raw ores or precursors).
  • In-process quality control (IPQC) procedures (e.g., sampling frequency during synthesis, testing indicators for intermediate products).
  • Finished product inspection protocols (e.g., which indicators are tested for each batch, testing methods—e.g., HPLC, ICP-MS, titration).
  • Batch record management rules (how they track each batch from raw material intake to finished product shipment).
• Traceability System: Ensure the supplier has a batch traceability mechanism. For example, each batch of chemicals should have a unique batch number that links to:
  • Source of raw materials (e.g., supplier of raw ores, certificates of raw materials).
  • Production parameters (e.g., temperature, pressure, reaction time for synthetic inorganic chemicals).
  • Test results of raw materials, intermediates, and finished products.
    This allows you to trace the root cause of quality issues (e.g., a batch with excessive impurities) quickly.

2. Analyze Batch-to-Batch Quality Data

• Certificate of Analysis (COA) Comparison: Ask the supplier to provide COAs for 5–10 consecutive batches of the target chemical (the more batches, the more representative the data). Focus on comparing key quality indicators:
  • Critical specifications: Purity (e.g., ≥99.9% for high-purity reagents), impurity content (e.g., heavy metals ≤10 ppm), moisture content, pH value, or physical properties (e.g., particle size distribution for inorganic powders).
  • Fluctuation range: Calculate the variation of each indicator across batches. For example, if the supplier claims a purity of "99.5% ±0.2%", check if all batches fall within this range—avoid suppliers with erratic results (e.g., one batch at 99.8%, the next at 99.1%).
• Third-Party Test Reports: For high-risk or high-value inorganic chemicals (e.g., ultra-high-purity silicon carbide for semiconductors), request the supplier to provide recent third-party test reports (from authoritative labs like SGS, Intertek, or national metrology institutes). Third-party data is more objective than in-house testing and can verify if the supplier’s self-reported COAs are accurate.
• Failure Rate Statistics: Ask the supplier for historical quality failure records (e.g., how many batches were rejected in the past year, reasons for rejection—e.g., impurity 超标，packaging damage). A low failure rate (<1–2% annually) indicates stable quality control.

3. Conduct On-Site or Video Audits of Production and Testing Facilities

• Raw Material Management:
  • Check if raw materials are stored separately by type and batch, with clear labels (e.g., "calcium carbonate raw ore, Batch No. 20240501").
  • Confirm raw materials are 100% inspected before use (not just sampled randomly). For example, ask to see inspection logs for recent raw material batches—do they record test results, inspector signatures, and rejection records?
• Production Process Control:
  • Observe if the production line follows standardized operating procedures (SOPs). For example, are operators monitoring key parameters (e.g., temperature for calcining alumina) in real time, and recording deviations?
  • Check if the supplier has measures to prevent cross-contamination (critical for high-purity chemicals). For example, are production lines for different grades (e.g., industrial vs. electronic grade) separated, or thoroughly cleaned between batches?
• Testing Lab Capabilities:
  • Evaluate the lab’s equipment: Do they have the necessary instruments to test your required indicators (e.g., ICP-OES for heavy metal detection, Karl Fischer titrator for moisture)? Are the instruments calibrated regularly (check calibration certificates with valid dates)?
  • Observe lab operations: Are technicians following standard testing methods (e.g., ASTM, GB/T)? Is there a system to verify test accuracy (e.g., using certified reference materials, or participating in inter-lab proficiency tests)?

4. Conduct Small-Batch Trial Orders and Independent Testing

• Trial Order Design: Place a small order (e.g., 10–20% of your monthly demand) and request the supplier to ship 2–3 separate batches (to simulate multi-batch purchases).
• Independent Verification:
  • Compare the COAs provided by the supplier with your own in-house test results (if you have a lab) or third-party tests you arrange. Focus on consistency: Do the supplier’s data match your independent test results?
  • Test "real-world applicability": For example, if you use inorganic chemicals as catalysts, check if the trial batches perform the same as your previous qualified supplies in terms of reaction efficiency or product yield—some subtle quality issues (e.g., trace impurities) may only appear in actual use.

5. Track Long-Term Quality Performance (Post-Cooperation)

• Batch-by-Batch Inspection: For each incoming batch, review the COA and conduct sampling tests (focus on critical indicators) to confirm compliance. Record results in a quality log.
• Fluctuation Trend Analysis: Every 3–6 months, analyze the quality data of all batches received (e.g., purity, impurity content) to identify trends. For example:
  • Are impurities gradually increasing over time (a sign of raw material degradation or lax process control)?
  • Do quality fluctuations correlate with external factors (e.g., seasonal changes in raw material supply, inorganic chemical suppliers production line maintenance)?
• Handling of Quality Incidents: Observe how the supplier responds to quality issues (e.g., a batch with unqualified purity). A stable supplier will:
  • Provide a timely root-cause analysis (not just blame "accidents").
  • Take corrective actions (e.g., adjusting raw material suppliers, optimizing testing procedures) and share verification results.
  • Compensate or replace defective batches as per the contract (no evasion of responsibility).

Key Red Flags to Watch For

• Expired or irrelevant QMS certifications.
• Incomplete batch records (e.g., missing raw material sources or test data).
• Large fluctuations in COA indicators across batches (e.g., purity ranging from 98.5% to 99.8% without explanation).
• Refusal to provide third-party test reports or allow on-site audits.
• Frequent quality incidents with no effective corrective actions.