Batch-to-Batch Consistency
To compare two lots of research material, put their specifications and lot reports side by side. Start with the exact entity and form. Then compare results only where the method, units and reporting basis answer the same question. Each laboratory decides whether it also needs a qualification check for its own assay.
Establish what stayed the same
Copy the sequence or structure, terminal groups, salt or complex form and amount basis from each specification. Check the document revision. A change in form or in how the mass is expressed can make a pair of percentages misleading before you reach the analytical result.
ICH Q6A describes a pharmaceutical specification in terms of tests, procedures and acceptance criteria. Two lots can meet the same limit while giving different numerical results. If a report gives only “pass”, record the decision and leave the measured value open. [1]
Build a comparison table from the reports
| Field | Lot A | Lot B | Comparison question |
|---|---|---|---|
| Product identity and form | Record as issued | Record as issued | Same defined material? |
| Specification version | Record reference | Record reference | Same requirements? |
| Analytical method | Record method | Record method | Comparable procedure and basis? |
| Result and units | Copy accurately | Copy accurately | Same attribute and reporting units? |
| Criterion | Record limit | Record limit | Same acceptance decision? |
| Document qualification | Record comment | Record comment | Does a limitation affect comparison? |
Use this worksheet with the two actual reports. Copy each method, result, unit and criterion exactly as issued. The certificate of analysis guide explains how to match the report to the correct lot. ICH Q7 section 11.4 gives a pharmaceutical example of the information a certificate identifies. [2]
Do not rank lots by one number
For example, one report may give HPLC peak-area purity and another peptide content by mass. Both use a percent sign, but their denominators differ. Keep the figures in separate rows and request a like-for-like result. The identity, purity and assay guide explains the distinction.
If performance in a particular assay determines acceptance, record the laboratory’s method, comparator and decision alongside its qualification result. A supplier release decision answers the supplier specification. The laboratory’s assay can impose a different requirement.
Record the transition
Give the transition a date in the lot log and connect the last container of the previous lot and the first container of the new one to their respective reports. If continued supply of the old lot is essential, make a same-lot enquiry before relying on availability.
For a proposed volume order, use institutional enquiries to state the number of containers, whether one lot is required and which records your purchaser needs to assess a proposed substitute.
Supporting checks
| Resource | Why open it |
|---|---|
| Batch Release, Quarantine and Rejection | Separate test results from a documented batch-release decision. |
| Batch Reports and Certificate Library | Request the document for the relevant product and lot. |
| Storage and Stability Across the Catalogue | Check what supports a material-specific storage condition or duration. |
| Institutional Supply | Separate organisational requirements from confirmed supply terms. |
Sources and scope
- ICH Q6A: Specifications, Test Procedures and Acceptance Criteria for New Drug Substances and New Drug Products Q6A defines a specification and distinguishes a test result from an acceptance criterion.
- Q7 Good Manufacturing Practice Guidance for Active Pharmaceutical Ingredients Q7 section 11.4 describes certificate content for active pharmaceutical ingredients. It supplies a reference for reading a report.