When doing peptide development, you need to choose a salt form that can be used in your future human clinical research and peptide testing.

The most common option is acetate as a counter ion. Overwhelmingly, acetate is better than hydrochloride.

However, certain residues may have an impact on which counter ions are better for the stability of the product. In most cases, peptides with free sulfhydryl groups are more stable to potential oxidizing impurities as hydrochlorides.

Acetate is often preferred because they produce a better lyophilized product. In early research and development, many peptides were used as trifluoroacetate.

Consider that as the project progresses, you will be changing the salt form according to the needs of the clinical product.

So to make it easier for you, you may want to consider starting with acetic acid to avoid this conversion.

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