ANALYSIS OF MODIFIED DEOXYNUCLEOSIDES BY ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

Electrospray mass spectra for selected modified deoxynucleosides and deoxynucleoside monophosphates have been determined. Protonated molecular ions are abundant in the positive ion spectrum, while (M-H)- appears in the negative ion spectrum. However, fragment ion intensities are usually low in both spectra. Conditions which promote collision-induced dissociation within the electrospray source facilitate fragment ion formation, and the intensity of BH2+ and S+ (positive ion spectrum) and (M-BH)- and B- (negative ion spectrum) are enhanced by increasing the skimmer cone voltage. MH+ was detected with as little as 3 pmol of deoxynucleoside, and the protonated molecular ion intensity is linear with respect to analyte concentration over two orders of magnitude.