ABSTRACT
Electrospray ionization is most commonly used in mass spectrometry for analysis of biological molecules such as peptides and proteins. However, peptides and proteins ions produced by electrospray ionization usually have multiple charges, and produce multiple spectrum peaks, making the mass spectrum complicated. Gas phase proton transfer ion/ion reaction can effectively regulate the charge states of peptides and proteins ions after electrospray ionization, simplifying the spectrogram, and thus is significant to the analysis of complex proteins and peptides samples. In this study, a dual-polarity linear ion trap ( LIT) mass spectrometer was used to control the charge state of peptide ions by proton transfer ion/ion reaction. The detection effect of the method was verified by using glutathione ( oxidation type) , oxytocin and dynorphin as typical samples. The results showed that this method could remove excess charges in the positive ions. When injecting enough negative ions for eaction, peptide ions with multiple charge valence state could be reduced to the minimum, therefore simplify the spectrogram effectively.