Measurements of Impurities in Liquids with a Nonvolatile Residue Monitor

The PMS (Particle Measuring Systems, Boulder, Colorado) nonvolatile residue monitor (NVR monitor) has been used to measure residues in isopropyl alcohol, tap water, and solutions prepared by dissolving different salts in deionized (DI) water. The instrument was operated in the batch and on-line modes mostly with the heater on. The manufacturer's calibration was confirmed with KCl solutions of different concentrations. The results show that the instrument responded linearly to the concentration change of solutes in DI water and had excellent repeatability. However, the instrument's response depends strongly on the solutes.