Negative ion chemical ionization (Cl−) mass spectra of amino acids

Negative ion chemical ionization (Cl−) mass spectra of the commonly occurring amino acids are simple and give information regarding molecular weight by the presence of [M + Cl]− adduct in the case of simple amino acids and [M − H]− in the case of amino acids containing additional polar groups. tert-Butyloxycarbonyl (BOC)-protected di-, tri- and tetrapeptides also given abundant [M + Cl]− ions.