The mass transport of species in the presence of oscillating flow is calculated for a flow generated by an oscillating pressure drop. Calculations have been done for several binary systems where two dilute species are transported in the presence of a carrier. It is observed that there are multiple frequencies of the imposed oscillation at which the total mass transport of each species is the same. These frequencies, called crossover frequencies, are obtained by way of a graphical intersection when the total mass transport is plotted against the imposed frequency. Explanations on the occurrence of these crossover frequencies are put forth in terms of time constants due to the kinematic viscosity, diffusion coefficients, and the periodicity of the flow. Consequently, these explanations give an idea of the separation of species in pulsatile flow.