Monitoring the Temperature of Dilute Aqueous Solutions Using Near-Infrared Water Absorption

Abstract

An alternative spectroscopic approach for monitoring the temperature of aqueous solutions is presented. The method is based upon the temperature-induced spectral changes undergone by the second overtone (around 960 nm) of the near-infrared (NIR) water absorption band. Single and multilinear regression analysis are tested in order to evaluate the predictive ability of temperature. A linear dependence is found when measurements are performed at a single wavelength, but a lower prediction error is obtained when multilinear models are applied. No matrix effects produced by moderately concentrated common dissolved ions are found in a broad range of pH. A signal-to-noise ratio allows a precision of 0.5 degrees C for temperature monitoring. A prediction error of 0.77 degrees C (single linear regression) and 0.25 degrees C (multilinear approach) are achieved in a range from 15 to 90 degrees C. Advantages in terms of instrumentation and data analysis required are discussed.

An Update on Novel Non‐Invasive Approaches for Periodontal Diagnosis

“…Furthermore, the 960-nm water band is known to shift with tissue temperature and changes in electrolyte concentration. 73 Thus, optical spectroscopy provides a measure of the hemoglobin-oxygen saturation of tissues and the degree of tissue perfusion as well as a measure of tissue edema.…”

Temperature imaging of sub-millimeter-thick water using a near-infrared camera

“…Given a practical concentration of each solute, however, the absorption bands of water would be still dominant and their spectra would not be deformed much. Otal et al [29] measured the temperatures of four dilute aqueous solutions (NaCl, NaHCO 3 , NaOH, and HCl 0.1 M solutions) using NIRS and found no significant effect on temperature predictions, despite slight changes in absorbance (an accuracy of 0.5 K was assured from 15 to 90°C). A lot of studies indicate that although the absorption band of glucose partly overlaps the m 1 + m 3 band of water, the change in absorbance due to temperature is larger than the change due to glucose in a practical concentration range.…”

“…The temperature dependence has been known in NIR spectrometry in biomedical, agricultural, and polymer sciences, but it has usually been regarded as a disturbance. While some experimenters have made use of it to measure the temperature of various samples that contain water [23,25,[28][29][30], others have tried to cancel out the temperature effect in noninvasive measurements of glucose concentration in vivo [31][32][33][34].…”

Infrared temperature measurements in micro-channels and micro-fluid systems

“…The temperature dependence has been known in NIR spectrometry in biomedical, agricultural, and polymer sciences, but it has usually been regarded as a disturbance. While some experimenters have made use of it to measure the temperature of various samples that contain water (Kakuta et al [42]; Lin and Brown [44]; Hollis et al [47]; Otal et al [48]; Thomson et al [49]), others have tried to cancel out the temperature effect in noninvasive measurements of glucose concentration (Arimoto et al [50]; Jensen et al [51]; Ye et al [52]; Cui et al [53]). …”