Table of Contents
When you’re sourcing pharmaceutical intermediates, the stakes are higher than most procurement decisions. A bad batch of intermediates doesn’t just mean a delayed shipment — it can contaminate an entire API production run, trigger regulatory scrutiny, or worse, compromise patient safety.
You already know you need to audit your supplier. But walking into a factory without a structured checklist is like conducting a financial audit without a spreadsheet. You’ll catch the obvious things and miss what actually matters.
We’ve put together this 30-point checklist based on what experienced buyers, QA auditors, and regulatory inspectors actually look for during intermediate supplier evaluations. It’s organized into six categories — print it, take it with you, and check every box.
A supplier’s paperwork tells you whether their quality system exists on paper or in practice. These six checks separate documented compliance from actual compliance.
Check Item | Why It Matters | What to Look For | |
1 | Quality Manual — not just a template | Many small manufacturers copy-paste a generic quality manual. If it references processes or equipment they don’t have, the entire system is suspect. | Ask to see the manual. Flip to a random SOP reference and ask them to show you the actual SOP. If they hesitate, that’s your answer. |
2 | Change control log — real, not cosmetic | Every process change — raw material source, equipment, solvent grade — should be documented with risk assessment and approval. A thin change log means either nothing ever changes (unlikely) or changes aren’t being recorded. | Request the change control log for the past 12 months. Pick one entry and trace it end-to-end: who initiated, who assessed risk, who approved, and whether re-validation was done. |
3 | OOS (Out-of-Specification) investigation records | A supplier that says “we never have OOS results” is either lying or not testing properly. Real manufacturing has deviations. The question is how they handle them. | Ask: “Show me your last three OOS investigations.” Look for root cause analysis, not just “re-test passed.” A well-documented OOS is a sign of an honest supplier. |
4 | Batch manufacturing records — complete and contemporaneous | BMRs should be filled out in real time, not re-created days later. Blank fields, correction fluid, or identical handwriting across dates are red flags. | Pick a recent batch. Check that every step has a timestamp, operator signature, and reviewer sign-off. Ask to see the raw data behind any hand-entered number. |
5 | Stability study data for the specific intermediate | ICH Q1A requires stability data to establish retest periods. If the intermediate is shipped internationally, temperature and humidity excursions during transit matter. | Request accelerated (40°C/75%RH) and long-term (25°C/60%RH) stability data. Check that the tested batches match the commercial scale, not just lab scale. |
6 | Regulatory inspection history — full disclosure | Past FDA 483s, Warning Letters, or EDQM deficiency letters reveal systemic issues. A supplier that voluntarily shares these (with corrective actions) is more trustworthy than one that hides them. | Ask directly: “When was your last regulatory inspection? What were the findings?” If they claim zero observations across multiple inspections, verify independently. |
A supplier’s QC lab is the single most telling room in the facility. These five checks reveal whether their “99% purity” claim means anything.
Check Item | Why It Matters | What to Look For | |
7 | HPLC method — purpose-built for the intermediate, not copied from an API monograph | Using a generic API method on an intermediate often misses route-specific impurities. The method must be validated specifically for that intermediate’s impurity profile. | Ask to see the method validation report (ICH Q2). Check for specificity: does the chromatogram show baseline separation between the main peak and known impurities? |
8 | Assay method vs. HPLC purity — are they reporting both? | HPLC area% purity can be misleading. A material showing 99.5% by HPLC could be 92% by assay if it contains non-UV-absorbing impurities (water, inorganics, salts). | Request both HPLC purity and assay (wt%) on the same COA. If the gap exceeds 2-3%, ask why. A supplier that only reports HPLC purity may be hiding something. |
9 | LC-MS capability for impurity identification | For complex intermediates (chiral, heterocyclic, multi-step synthesis), unknown impurity peaks need structural identification. “It’s below 0.1% so we ignore it” is not an acceptable answer for regulatory filings. | Ask: “Do you have in-house LC-MS? Show me the last unknown impurity you identified.” If they outsource all impurity ID to a third-party lab, turnaround time becomes a supply chain risk. |
10 | Residual solvent testing — GC with validated methods | ICH Q3C classifies solvents by toxicity. Class 1 solvents (benzene, carbon tetrachloride) are prohibited. Class 2 solvents have strict PDE limits. Many small suppliers skip this test entirely. | Check the COA for residual solvent results. If missing, ask why. If present, verify the GC method can detect the specific solvents used in their synthetic route — a generic headspace method may miss high-boiling solvents like DMF or DMSO. |
11 | Heavy metal / elemental impurity testing (ICH Q3D) | Palladium, platinum, nickel, and other catalyst residues are common in intermediate synthesis. ICH Q3D sets strict PDE limits based on route of administration and duration of therapy. | Ask which elemental impurities they test for and by which method (ICP-MS preferred over the old USP <231> colorimetric test). If they can’t produce an elemental impurity profile, they’re not ready for regulated markets. |
Documents can be polished. The production floor cannot. These six items require walking the facility with your eyes open.
Check Item | Why It Matters | What to Look For | |
12 | Dedicated vs. multi-purpose equipment — and cleaning validation | Multi-purpose equipment is common and acceptable, but cross-contamination risk must be managed. The cleaning validation program is what makes or breaks this. | Ask: “What product was made in this reactor before this batch?” Then ask to see the cleaning validation report for that product changeover. Look for swab test results, not just visual inspection. |
13 | Equipment calibration status — check dates yourself | Expired calibration stickers on pressure gauges, thermocouples, or balances are the most common GMP deficiency found during audits — and the easiest to spot. | Walk the production floor. Randomly check 5-10 instruments. If you find an expired calibration tag, ask when it was last used for a production batch. One expired gauge in a critical location is a finding. Three is a pattern. |
14 | Material flow and segregation — from receiving to shipping | Quarantined materials, rejected materials, and approved materials must be physically segregated. Mixing them up is a fundamental GMP failure. | Walk the warehouse. Look for clear signage: “Quarantine,” “Released,” “Rejected.” Check that rejected materials are in a locked cage or clearly cordoned-off area — not just sitting on a pallet with a handwritten note. |
15 | Environmental controls — temperature, humidity, and cleanroom classification | Many intermediates are hygroscopic or temperature-sensitive. Storage conditions claimed on the COA must match reality. For sterile or HPAPI intermediates, cleanroom classification is non-negotiable. | Bring a portable temperature/humidity logger if possible. Check that storage area conditions match what’s on the COA. For classified cleanrooms, ask to see the most recent particle count and viable monitoring reports. |
16 | Waste handling and solvent recovery practices | Solvent recovery is cost-effective, but recovered solvents must meet the same specifications as fresh solvents. Uncontrolled recovery can introduce new impurities that accumulate batch over batch. | If they recover solvents, ask: “How do you qualify recovered solvent? Do you set tighter limits than fresh solvent? How many recovery cycles before you discard?” No documented recovery program = risk of cross-contamination. |
17 | Utility systems — water, compressed air, nitrogen | Process water quality (purified water vs. WFI) matters for intermediates used in injectable API synthesis. Compressed air and nitrogen that contact product must be free of oil, particles, and moisture. | Ask to see the water system qualification report and routine monitoring data. Check compressed gas filters — are they replaced on schedule? A rusty compressed air line is not just ugly; it’s a contamination source. |
You’re not just buying from a manufacturer — you’re buying from their entire upstream supply chain. These five checks map that chain.
Check Item | Why It Matters | What to Look For | |
18 | Raw material supplier qualification — not just a vendor list | Your intermediate supplier’s quality is only as good as their starting material suppliers. If they can’t tell you who makes their key raw materials and how they qualify them, you’re flying blind. | Ask for the approved supplier list for the key starting materials of your intermediate. Pick one supplier and ask: “When was the last audit? Who conducted it? Show me the audit report.” |
19 | Supply chain mapping — can they trace every input? | For regulatory filings (DMF, CEP, ANDA), you need to demonstrate full traceability from starting material to finished intermediate. Gaps in the supply chain map will be flagged during regulatory review. | Ask them to draw the supply chain map for your intermediate — every raw material, every supplier, every intermediate step. Check for single-source dependencies. A single-source key starting material is a supply risk. |
20 | Shipping validation — especially for temperature-sensitive intermediates | An intermediate that leaves the factory at 99.5% purity can arrive at 96% if shipping conditions aren’t validated. Temperature excursions during sea freight (40°C+ in a container) can degrade product. | Ask: “Have you validated the shipping conditions for this intermediate? What’s the worst-case temperature during transit?” If they ship internationally, request a shipping validation study or at minimum a temperature data logger report from a recent shipment. |
21 | Business continuity — what happens if their key raw material supplier stops? | The pharma supply chain is fragile. A single raw material disruption can halt intermediate production for months. Suppliers should have contingency plans. | Ask: “If your main supplier of [key raw material] suddenly couldn’t deliver, what’s your backup plan? How long would it take to qualify an alternative?” No plan = supply risk you’re inheriting. |
22 | Packaging integrity and labeling | Intermediate packaging must protect against moisture, light, and physical damage. Labels must include GHS hazard symbols, storage conditions, batch number, and net weight — all legible and durable. | Inspect finished product packaging in the warehouse. Are drums sealed with tamper-evident seals? Are labels weather-resistant (not inkjet that smudges in humidity)? Check that the label batch number matches the COA. |
Data integrity is now the single most-cited GMP deficiency globally. These four checks target the most common failure points.
Check Item | Why It Matters | What to Look For | |
23 | Audit trail — enabled and reviewed | FDA and other regulators now expect full audit trails on all chromatography data systems (CDS). If audit trails are turned off, or if no one reviews them, the data cannot be trusted. | In the QC lab, ask an analyst to open a recent HPLC data file and show you the audit trail. Check: Is it enabled? Does it show who injected, who processed, and whether any integration parameters were changed? Ask the QA manager: “Who reviews audit trails, and how often?” |
24 | Unique user accounts — no shared logins | Shared or generic user accounts mean you can never prove who performed a specific test or entered a specific result. This is a fundamental data integrity failure. | Ask to see the user account list for the CDS and LIMS (if used). Check for accounts named “QC1,” “Analyst,” “Admin,” or other generic names. Each user should have a unique, named account with role-based permissions. |
25 | Electronic data backup and disaster recovery | Raw data files stored only on a single instrument PC are one hard drive failure away from being lost. Regulators expect secure, redundant backup. | Ask: “Where is your raw analytical data stored? How often is it backed up? Can you restore a data file from six months ago and show it to me?” If they can’t answer confidently, data integrity is at risk. |
26 | Integration practices — manual integration must be justified | Manual re-integration of chromatograms (changing baseline, suppressing peaks, adjusting peak areas) can hide impurities. While sometimes technically justified, it must be controlled and documented. | Ask: “What’s your policy on manual integration? Show me the last instance where an analyst manually re-integrated a chromatogram.” A proper system requires a pre-approved reason, supervisor approval, and audit trail documentation of both the original and re-integrated result. |
Technical quality matters, but a supplier who can’t communicate clearly or who plays games with commercial terms will cost you more in the long run than a slightly lower purity.
Check Item | Why It Matters | What to Look For | |
27 | Technical communication — can their team answer your questions directly? | When you ask a technical question and get passed through three people before getting a vague answer, it signals a weak technical team — or worse, a team that’s hiding something. | During the audit, ask a specific technical question about their synthetic route (e.g., “What’s your typical impurity profile at this step, and how do you control the des-chloro impurity?”). A good supplier’s chemist can answer immediately. |
28 | Sample consistency — is the audit sample representative of commercial production? | A common trick: the “golden sample” produced under ideal lab conditions, not representative of what you’ll actually receive at commercial scale. | Ask: “Was this sample pulled from a commercial-scale batch or a lab-scale demo batch?” Request the batch record for the sample batch and check the scale. If the sample is 50g and commercial batches are 50kg, ask for process equivalency data. |
29 | MOQ and lead time transparency | Hidden MOQ requirements or unrealistic lead times that suddenly extend after the first order damage your production planning. | Ask: “What’s your typical lead time from PO to shipment for this intermediate? What’s the minimum order quantity, and is it negotiable for repeat orders?” Get it in writing. If they won’t commit to a range, they’re either disorganized or planning to bait-and-switch. |
30 | After-sales support — what happens when something goes wrong? | A batch that fails your incoming QC is a problem. How the supplier handles it tells you everything about their commercial integrity. | Ask: “If we receive a batch that doesn’t meet the agreed specification, what’s your process? Who do we contact? What’s your typical resolution timeline?” A supplier that says “that never happens” instead of describing their CAPA and return process is not being honest. |
Before the audit: Review the checklist and mark items that are especially critical for your specific intermediate. A chiral intermediate? Focus on Category 2 (especially item 11 — chiral purity). A high-temperature synthesis? Focus on Category 3 (especially item 15 — environmental controls).
During the audit: Don’t just read the questions. Walk the floor. Open cabinets. Talk to operators, not just managers. The most valuable information often comes from the things people say when they forget you’re auditing them.
After the audit: Score each category. A supplier that passes all six categories with minimal findings is rare — and valuable. But don’t expect perfection. What matters more than a perfect score is how the supplier responds when you point out gaps. Do they get defensive, or do they say “you’re right, here’s how we’ll fix it”?
This checklist was developed by the Tianming Pharma quality team based on 15+ years of experience manufacturing pharmaceutical intermediates, hosting customer audits, and undergoing regulatory inspections. We use these same standards to evaluate our own raw material suppliers — because we know that our customers’ trust depends on the quality of every input.
Have questions about a specific intermediate or want to discuss an audit?
Contact our team — we’re happy to walk through your requirements, share relevant documentation, and schedule a facility visit.
Statement
Written by the Tianming Pharma Quality & Technical Team. Updated: June 2026. This checklist reflects current ICH guidelines (Q7, Q11, Q3A-Q3D, Q2, M7) and GMP requirements as of the date of publication. Always verify regulatory requirements against the latest versions applicable to your specific product and market.
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