Simultaneous Determination of Physical and Chemical Properties of Sodium Chloride Solutions by near Infrared Spectroscopy

Abstract

Near infrared (NIR) spectroscopy has been investigated as a new technique for the simultaneous determination of physical and chemical properties of NaCl solutions. The spectra of NaCl solutions (0 to 5 M) were measured with cuvettes in the 1100–2500 nm and 680–1230 nm regions at temperatures between 23.0 and 28.5°C, and with a fibre-optic probe in the 1100–1870 nm region at room temperature (23.0 ± 0.5°C). These spectra were correlated with various properties of NaCl solutions by principal component regression (PCR) and multilinear regression (MLR) models. The properties studied include water concentration, density, refractive index, relative viscosity, freezing point depression, osmolality, electrical conductance and activity coefficient of NaCl. Very good correlations were found between the NIR predicted values and literature values. The results of this study demonstrate that several properties of NaCl solutions can be determined simultaneously with NIR spectroscopy. Remote sensing of the properties can be performed with the use of a fibre-optic probe.