Select the laboratory for competence and scope
Use a mutually accepted, established laboratory with relevant peptide and method experience. Accreditation can support competence, but the exact accredited or validated scope and the molecule-specific procedure still need review.
Make the samples and methods comparable
Define who samples the lot, how samples are sealed and shipped, which method version is used, how the sample is prepared and how results are rounded. Without those controls, a numerical difference may reflect procedure rather than material quality.
- Named laboratory and chain of custody
- Sample quantity, container and storage
- Method version and system suitability
- Specification, rounding and uncertainty rule
- Retest or referee-laboratory process
- Testing cost and documented remedy
Investigate disagreement before assigning fault
When results differ, compare raw data, chromatographic conditions, standards, integration and preparation records. The signed terms should state how confirmed supplier-attributable nonconformance is resolved, which may include replacement, credit or refund.