SEPARATION AND IDENTIFICATION OF POSITIVELY CHARGED AND NEUTRAL NUCLEOSIDE ADDUCTS BY CAPILLARY ELECTROCHROMATOGRAPHY MICROELECTROSPRAY MASS-SPECTROMETRY

Capillary electrochromatography (CEC) is shown to be capable of separa ting mixtures containing both positively charged and neutral styrene o xide-adenosine adducts. In a study of the mechanism of deamination of positively charged 1-(2-hydroxy-1-phenylethyl) adenosine using O-18-la beled water, possible contamination of the chromatographically purifie d deamination product, 1-(2-hydroxy-1-phenylethyl:) inosine, with the positively charged 1-(2-hydroxy-1-phenylethyl) adenosine was observed. Because the deamination product and the presumed contamination have t he same molecular weights and similar structures, CEC-microelectrospra y mass spectrometry (CEC-mu ESI/MS) was used to confirm the presence a nd identity of the suspected impurity. A trace amount of the positivel y charged 1-(2-hydroxy-1-phenylethyl) adenosine, which could not be ob served by either HPLC-UV or CEC-UV, was detected by CEC-mu ESI/MS. Thi s discriminatory ability of CEC-mu ESI/MS is attributed to the fact th at positive ion mode ESI-MS is a more sensitive detector for a positiv ely charged compound than a UV detector, and that the combination of e lectroosmotic and electrophoretic flows and hydrophobic interactions w ith the stationary phase contributes to the separation of the positive ly charged compound. As a result, the positively charged compound was observed to elute much earlier and with much sharper peaks than the ne utral compounds for which electroosmotic flow is the only ''pumping'' force for the solvent. (C) 1998 American Society for Mass Spectrometry .