Capillary electrochromatography with novel stationary phases. 3. Retentionbehavior of small and large nucleic acids on octadecyl-sulfonated-silica

In this investigation, the potentials of porous and nonporous octadecyl-sul fonated-silica (ODSS) microparticles were demonstrated in the capillary ele ctrochromatography (CEC) of small (e.g., nucleotides and dinucleotides) and large (e.g., transfer ribonucleic acids (t-RNAs)) nucleic acids. The ODSS stationary phase comprised two layers: a hydrophilic sulfonated (permanentl y charged) sublayer and an octadecyl top layer. While the sublayer is to pr ovide a relatively strong electroosmotic now, the octadecyl top layer is to ensure the retentivity and selectivity required for the separation of the analytes. Mono-, di-, and triphosphate nucleotides were best separated when a small amount of tetrabutylammonium bromide was added to the mobile phase . The tetrabutylammonium bromide functioned as an ion-pairing agent and con sequently allowed the rapid separation of 12 different nucleotides, It is b elieved that the dynamic complex exchange model explains the basis of reten tion in ion pair reversed-phase CEC, Eight different dinucleotides, which h ave similar mass-to-charge ratios, separated very well by CEC, These solute s exhibited similar migration times (i.e., little or no separation) in capi llary zone electrophoresis (CZE), Similarly, t-RNAs that did not separate b y CZE were well resolved in CEC with nonporous ODSS, This demonstrates that CEC is very suitable for the separation of solutes that have similar mass- to-charge ratios but differ in their hydrophobicity.