A modified golden gate attenuated total reflection (ATR) cell for monitoring phase transitions in multicomponent fluids at high temperatures

A new continuous flow method using attenuated total reflection infrared (ATR-IR) spectroscopy has been developed for monitoring phase transitions in multicomponent fluids at high pressures and temperatures. Our approach uses Fourier transform infrared (FT-IR) and a modified Golden Gate attenuated total reflection (ATR) cell and exploits the fact that the absorbance of a vapor is much lower than that of the corresponding liquid to monitor the phase transition between vapor and liquid. We demonstrate that this method can provide quantitative measurements on both the dew point and the bubble point. We have validated our approach using three single-component systems (EtOH, MeOH, and H₂O) and a binary system of EtOH + H₂O, monitoring phase transitions at temperature up to 300°C and pressure up to 10 MPa.