> For the complete documentation index, see [llms.txt](https://docs.rplpeptides.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rplpeptides.com/docs/glossary/laboratory-terms/quality-control.md).

# Quality Control

## Definition

Quality Control (QC) is the set of procedures and activities used to verify that a product meets defined quality specifications through testing, inspection, and documentation.

## Overview

QC is the operational arm of quality assurance. While quality assurance (QA) focuses on building quality into processes, QC focuses on testing and verifying that the final product meets specifications.

## Technical Explanation

**QC Testing Flow for Peptides:**

1. **Incoming:** Raw material verification
2. **In-Process:** Monitoring during SPPS, purification, lyophilization
3. **Final:** Complete testing of finished product (HPLC, MS, appearance, pH, etc.)
4. **Stability:** Periodic re-testing during storage

**Typical QC Tests per Batch:**

| Test              | Purpose                                |
| ----------------- | -------------------------------------- |
| HPLC Purity       | Quantify target peptide vs. impurities |
| Mass Spectrometry | Confirm molecular weight (identity)    |
| Appearance        | Visual inspection of powder            |
| pH                | Solution pH (if applicable)            |
| Water Content     | KF or LOD                              |
| Assay             | Peptide content (w/w)                  |
| Endotoxin         | LAL test (if required)                 |
| Residual Solvents | GC analysis                            |

**QC Record Keeping:** Each test generates a record that is linked to the batch number, forming the basis of the COA.

## Importance in Peptide Documentation

QC test results are the foundation of the COA. The presence of comprehensive QC data demonstrates a supplier's commitment to quality. Researchers should evaluate QC scope when selecting suppliers.

## Related Terms

* [COA](/docs/glossary/quality-control/coa.md)
* [Quality Assurance](/docs/glossary/laboratory-terms/quality-assurance.md)
* [Specification](/docs/glossary/quality-control/specification.md)

## Frequently Asked Questions

**Q: Is QC the same as QA?** A: No. QC (testing/verification) detects issues in finished products. QA (process management) prevents issues from occurring. Both are essential for overall quality.

**Q: How long does QC testing take?** A: Complete QC testing for a peptide batch typically takes 1–3 business days, including HPLC analysis, MS confirmation, and documentation.


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