A device is provided in a supercritical fluid system, which uses a mobile phase output by a separation device, the mobile phase volumetrically expanding as it decompresses. The device includes a passive splitter and a shuttle valve. The passive splitter is configured to receive the mobile phase and to split the mobile phase into a primary flow stream and a split flow stream, where the primary flow stream is directed to a pressure maintenance device. The passive splitter is further configured to reduce pressure of the split flow stream, causing volumetric expansion of the split flow stream. The shuttle valve is configured to insert volumetric aliquots of the volumetrically expanded split flow stream into a dilution flow stream to provide a diluted split flow stream, and to direct the diluted split flow stream to a low pressure detector.