Run HPLC system suitability before samples

Practice the USP <621> suitability order. Unknowns are not injected until a blank and the required SST injections meet criteria.

1. Equilibrate the column with the mobile phase to a stable baseline.
2. Inject a blank and confirm no interfering peaks.
3. Inject the system-suitability standard the required number of times.
4. Compare resolution, tailing, and precision to the method limits.
5. Do not start samples if suitability fails; troubleshoot and repeat SST.
6. Inject samples with the required bracketing standards.
7. Review the sequence.
8. Sign the run log.