We have developed an interferometric lithography technique to manufacture an integrated micro-nano-fluidic chip for use in bioseparations and sensing. Transport behavior of two dyes, one charged and one neutral, in these silica/silica oxide/Pyrex chips has been quantified. A mixture of the dyes was introduced into an array of nanoscale channels using electroosmosis through the microfluidic channels. Electrokinetic separations of the dyes in these nanochannels at various applied biases were examined in different chips with nanochannel widths ranging from 50-200 nm. Confocal laser scanning microscopy was used to observe the average velocities of the dyes in the array of nanochannels. The resulting velocities were in good agreement with theoretical predictions that take into account the wall surface potential overlap and electrolyte concentrations across the individual nanofluidic channels. Separations were also achieved in these channels by the application of pressure, utilizing the Poiseuille velocity distribution of fluid within the channels.