Is a sodium adduct a counter-ion in the solid?

Not in the sense used here. Sodium and potassium adducts are mass shifts the spectrum may name. The salt form is the phrase on the purity or mass section of the PDF.

Does the counter-ion appear in the area percent?

Not as a peptide peak you can assume. Area percent and salt form are separate lines. Record each one only when the file states it.

Glossary · 2026-09-24

Scientific lead: Alice Kay, Ph.D.

Peptide counter-ion, laboratory definition

A counter-ion is the ion that pairs with a charged peptide in the isolated solid. Trifluoroacetate and acetate are the two this site's COA notes name most often. The counter-ion is not an impurity story you invent, and it is not the peptide sequence. It does change the mass of the species and the peptide share of a gross weight when the report accounts for it.

If the file names the counter-ion, copy it beside the TFA salt or acetate salt language. If the file does not, leave the line blank. Do not borrow a factor from another lot. See the reading guide. Research-use only.

Frequently asked questions

Is a sodium adduct a counter-ion in the solid?: Not in the sense used here. Sodium and potassium adducts are mass shifts the spectrum may name. The salt form is the phrase on the purity or mass section of the PDF.
Does the counter-ion appear in the area percent?: Not as a peptide peak you can assume. Area percent and salt form are separate lines. Record each one only when the file states it.

Research-use only. BlueNex Labs does not provide medical or veterinary advice. Confirm your institution’s policies before purchase.