Approach to quasi stationary electrokinetic chromatography

A partial filling (PF) electrokinetic chromatography (EKC) system in combination with the application of weak counter pressures was built up by the combination of an UV-active polymeric dye, Poly R-478, used as additive in the separation buffer (SB) zone and an UV-permeable borate background buffer (BB). The electroosmotic flows of the buffers were equalized by matching their ionic strengths to achieve best efficiency. The influence of the pressure for the injection of the separation buffer and the effect of the counter pressure on the breakthrough of the separation buffer zone was investigated. The quasi stationary state of the separation buffer zone was evaluated by recording breakthrough curves. Based on these data the counter pressure was manipulated so that the separation buffer zone became quasi stationary and a large interference-free migration time window results. The system was optimized using a mixture of amino/nitroaromatics as test compounds.