Microbore high performance liquid chromatography–ion spray mass spectrometry for the determination of peptides

Microbore high performance liquid chromatography‐ion spray mass spectrometry is demonstrated for the determination of peptides. The ion spray mass spectra of peptides contained primarily only (M + nH)n+ ions (n is the degree of protonation). The linearity for a dilution series of leucine enkephalin was determined to be 4.9 orders of magnitude (r = 0.990), from 29 fmol to 90 pmol injected, and the smallest discernible signal (S/N of 3/1) was 65 amol. The tandem mass spectrometry daughter‐ion mass spectrum of the multiply‐charged molecular ion of dynorphin 1–9 exhibited daughter ions consistent with the sequence of the peptide. The micro‐LC gradient elution separation for a tryptic digest of recombinant bovine somatotropin was acquired. The mass spectra obtained from the components in the tryptic digest were consistent with previously identified peptides. The mass spectrum of the tryptic fragment ISLLLIQSWLGPLQFLSR (MW 2083) contained multiply‐charged ions that made it possible to detect this fragment even though its molecular weight is beyond the mass range of the mass spectrometer.