A method for confirming the sequence of a
nucleic acid is provided, comprising: (i) hydrolytic cleavage of predetermined phosphodiester bonds in the
nucleic acid to generate a plurality of oligonucleotides; (ii)
ionization of the plurality of oligonucleotides to provide a
gas phase of ionized oligonucleotides, wherein a majority of the ionized oligonucleotides are singly charged; (iii) isolation of the ionized oligonucleotides using a plurality of
mass-to-charge ratio (m / z) windows; (iv) detection of the isolated ionized oligonucleotides of each m / z window using a high-resolution
mass spectrometer (HRMS) with a resolution of more than 30.000 at m / z 200, thereby obtaining a
mass spectrum; (v) Confirming the sequence of the
nucleic acid by comparing the
mass spectrum obtained in step (iv) with a
mass spectrum determined
in silico after the same hydrolytic cleavage of the nucleic acid as in step (i), the confirmation comprising a comparison of the
signal intensities of one or more mass envelopes resulting from the ionized oligonucleotides.