Viscosity measurements of methanol-water and acetonitrile-water mixtures at pressures up to 3500 bar using a novel capillary time-of-flight viscometer

A new type of viscometer based on the Poiseuille flow principle has been developed that is capable of measuring solution viscosities at ultrahigh pressures. The capillary time-of-flight (CTOF) viscometer has been used to measure the viscosity of methanol-water and acetonitrile-water mixtures in decade volume% increments from atmospheric pressure to 3500 bar (50,000 psi), at 25 degrees C. This instrument works by utilizing a relatively small pressure drop (similar to 200 bar) across a capillary which has both inlet and outlet pressurized so that the average column pressure can be significantly elevated (up to 3500 bar). Measurements from the CTOF viscometer match high-pressure viscosity data collected previously using falling-body viscometers of the Bridgman design. This manuscript serves to bring viscosity data at ultrahigh pressures for the two most common liquid chromatographic mobile phases into the chromatographic literature. (c) 2006 Elsevier B.V. All rights reserved.