Abstract

The concentrations of NaCl in aqueous solutions have been determined with the use of near-IR spectra between 1100 and 1900 nm. Models expressing the concentration of NaCl are developed with linear and nonlinear regression with the use of the absorbances at selected wave-lengths and with principal component regression (PCR) using entire spectra. Temperature perturbations on water bands interfere with the measurement of NaCl but can be removed by linear or nonlinear regressions using the absorbances at the wavelengths where the temperature effects are zero, or they can be accounted for by PCR. Standard errors of 5 mM and a detection limit of 15 mM are obtained for NaCl. This technique can be applied for quantitative analysis of NaCl in the laboratory or can be readily adapted for continuous monitoring in process control.

Optical Constants in the Infrared for Aqueous Solutions of NaCl†

Marvin R. Querry, Richard C. Waring, Wayne E. Holland, G. Michael Hale, and William Nijm
J. Opt. Soc. Am. 62(7) 849-855 (1972)

Temperature measurements of turbid aqueous solutions using near-infrared spectroscopy

Naoto Kakuta, Hidenobu Arimoto, Hideyuki Momoki, Fuguo Li, and Yukio Yamada
Appl. Opt. 47(13) 2227-2233 (2008)

Return-path, multiple-principal-angle, internal-reflection ellipsometer for measuring IR optical properties of aqueous solutions

R. M. A. Azzam
Appl. Opt. 49(25) 4710-4714 (2010)

Matrix effect of sodium compounds on the determination of metal ions in aqueous solutions by underwater laser-induced breakdown spectroscopy

Christian Goueguel, Dustin L. McIntyre, Jinesh Jain, Athanasios K. Karamalidis, and Cantwell Carson
Appl. Opt. 54(19) 6071-6079 (2015)

Determination of Ca and Mg in aqueous solution by laser-induced breakdown spectroscopy using absorbent paper substrates

Dehua Zhu, Lizhi Wu, Bin Wang, Jianping Chen, Jian Lu, and Xiaowu Ni
Appl. Opt. 50(29) 5695-5699 (2011)