High-Performance Liquid Chromatography so purity and concentration.

Back when I started few people were doing this and it was more of a risk, I was buying from research peptide vendors who had their own testing practices, but now a huge number of people are doing it and there are markets where reputations matter and it appears to be reasonably efficient.

I would prefer not to inject peptides from gray market China but practically all of the gray/black market supply is from there. I will likely switch to pharma grade when generics become available.