CHROMATOGRAPHIC ANALYSIS WITH LOW PRESSURE DUAL GRADIENT REFOCUSING

There is provided a system for separation of analytes in a solution. The system encompasses a cartridge or trapping column enclosing a sorbent for binding the analytes in the solution and a conduit establishing a fluid link to a valve having a holding-loop to achieve elution through the cartridge at low pressures. Prior to entry into the loop, the eluent is diluted or modified by a confluent flow stream. The valve is switchable to a position following the elution from the cartridge for emptying the holding loop through an outlet port at high pressures comparable to those required for chromatographic columns. The system may use parallel gradient formation/elution to stagger analyses so that essentially the only analytical phase that hinders a 100% duty cycle is the time required for moving the first analyte from the valve and to the detector.