That's a pretty common misunderstanding about the tests.
First, the easy part. It's not 14.8 'strength'. There are 14.8mg of tirz in the vial. Small difference, but kinda important for dosing.
Second, 'Purity' is the most misunderstood. Think of it this way... it's a chemist's term. When you get a lab test, it's usually an HPLC test. It's specific to the peptide. It DOES pick up other things, which show up on a graph during the test. Everything found is sorted as target peptide, known additives, and unknown additives. Purity = (target peptide) / (total found - known additives).
Say a vial has tirz/sugar/a preservative/ some cleaner.
The test shows tirz and sugar. The lab knows what that should look like. The preservative is new, so it shows up. The lab will ask if you know what it is, and if you want to pay to identify it. If it's identified and used in other peps, it's added to the 'known' list. Otherwise, it's excluded from the purity calculation but noted on the report. A lot of the 'unknown' stuff is just broken-down tirz.
Now, the cleaner might not even show up. It doesn't affect the purity. Most possibilities are like this.
How do you know about other contaminants? You can pay the lab to test for almost anything, but each test is specific and costs money. Fortunately, we know enough about peptide making that heavy metals probably aren't in them, and they've been tested for sometimes and never show up.
