Simultaneous Determination of Monoatomic Ions via Infrared Attenuated Total Reflection Spectroscopy in Aqueous Solution at Different Temperatures.

In this study, monoatomic and thus IR-inactive ions were determined via infrared attenuated total reflection (IR-ATR) spectroscopy including Cl-, Na+, Mg2+, Ca2+, K+ and Br-, next to the IR-active ion SO42-. The determination of IRinactive ions is enabled, as each ion influences the infrared spectrum of bulk water by organizing the water molecules within the solvation shell around the ionic species in a unique way. Furthermore, the influence of temperature was taken into account for the potential application of this analytical technique in real-world scenarios. Using chemometric data analysis, seven ions could be discriminated at temperatures ranging between 3°C and 45°C. Finally, within a sample of seawater, Cl-, Na+, Mg2+ and SO42- could be simultaneously quantified, while the concentrations of Ca2þ, Kþ and Br remained below the achievable limits of detection. [ABSTRACT FROM AUTHOR]