DETERMINATION OF PYRIMIDINE CYCLOBUTANE DIMERS BY ELECTROSPRAY IONIZATION ION TRAP MASS-SPECTROMETRY

A straightforward approach for determining the cyclobutane pyrimidine dimers, thymine-thymine, uracil-thymine, and uracil-uracil, based upon electrospray ionization/ion trap mass spectrometry is described. These compounds are detected as the sodiated molecules, [M + Na]+, the response for which is maximized by adding low concentrations of sodium salts to the electrospray solutions. Under these conditions subnanogram levels of the dimers are determined by flow injection analysis. Structural information is obtained by collision-induced dissociation of the lithium adducts, [M + Li]+, which are formed by adding lithium salts to the solvents.