Abstract: A self-adjusting, free-flowing pneumatic nebulizer interface is described for coupling fluid phase separation apparatus such as capillary electrophoresis apparatus or fluid-phase analyte delivery apparatus such as flow-injection analysis apparatus to gas phase, post-separation detection apparatus such as mass spectrometers, chemiluminescence detectors, or other similar gas phase detection apparatus. The interface combines the analytes with only the needed amount of sheath fluid to produce a combined flow whose magnitude automatically matches the self-aspiration rate of the pneumatic nebulizer interface, and which is combined with a gas flow to produce an aerosol. The resulting aerosol can then be either deposited directly on a surface, forwarded directly to a detection system or forwarded first to a conversion apparatus such as an oxidizer and the oxidized sample components are then forwarded to a detector.