How do I know the vial contains the peptide I ordered?

You confirm identity, not just purity. HPLC tells you how pure the main peak is, but mass spectrometry (LC-MS) is what proves the molecule is actually the peptide you ordered — it matches the measured molecular mass to the expected value. A product can be highly "pure" yet be the wrong compound, so a COA without an MS identity result leaves the key question unanswered. The strongest confirmation is a batch-specific COA from a named independent lab whose unique key you can verify on the lab's own portal (for example, Janoshik), showing the compound name and molecular mass for your specific lot. Without independent identity testing, you are trusting the label.