The Optilab UT-rEX is an RI detector specifically designed for use with UHPLC systems using columns packed with small beads. The Optilab UT-rEX uses a combination of miniaturized components and semiconductor photodiode technology as well as computer algorithms. Due to the extremely small volumes of UHPLC, the dead volume for the instrument is <1.5 µL, allowing for good resolution. In addition to the instrument having no range or gain setting, the full range of instrument detection is always present and the full sensitivity exists over the entire range. The small flow cell and temperature regulation enable stable RI baselines and RIS signals.