ELECTROSPRAY-CONDENSATION PARTICLE COUNTER - A MOLECULE-COUNTING LC-DETECTOR FOR MACROMOLECULES

A new detector for macromolecular separations is described. The detect or counts individual macromolecules (molecular weights greater than ab out 10 000) and reports counts per second. The chromatographic effluen t is electrosprayed, neutralized, and swept to the detector by a strea m of air. The detector is a condensation particle counter that detects individual particles by light scattering from droplets condensed on t he particles. When used as the detector for a size exclusion separatio n of proteins, the detector has a linear range of 4 orders of magnitud e with detection limits as low as 0.1 mu g/mL. The detector can be dir ectly interfaced (no makeup flow) with effluent flows as low as 10 nL/ min. A Monte Carlo model based on size measurements of the electrospra yed droplets correctly predicts the observed detector behavior.