Temperature measurements of turbid aqueous solutions using near-infrared spectroscopy

Abstract

We report a method that uses near-infrared spectroscopy and multivariate analysis to measure the temperature of turbid aqueous solutions. The measurement principle is based on the fact that the peak wavelength of the water absorption band, with its center near 1440 nm, shifts with changes in temperature. This principle was used to measure the temperatures of 1 mm thick samples of aqueous solutions containing Intralipid (2%), which are often used as optical phantoms for biological tissues due to similar scattering characteristics. Temperatures of pure water and aqueous solutions containing glucose (100 mg/ml and 200 mg/ml) were also measured for comparison. For the turbid Intralipid solutions, the absorbance spectrum varied irregularly with time due to the change in scattering characteristics. However, by making use of the difference between the absorbance at 1412 nm and the temperature-independent absorbance at 1440 nm, we obtained SEPs (standard error of prediction) of 0.3 degrees C and 0.2 degrees C by univariate linear regression and partial least squares regression, respectively. These accuracies were almost the same as those for the transparent samples (pure water and glucose solution).

Temperature-dependent optical properties of Intralipid® measured with frequency-domain photon-migration spectroscopy

“…1 Other applications include the estimation of temperature from the change in optical, property measured. Temperature can be estimated from changes in the absorbance 2 however, in turbid media, variation in scatter introduces an uncertainty in the path length, making it difficult to reliably estimate temperature from optical extinction coefficients. Uncoupling the effect of scattering on absorption may reduce this obscurity, offering the potential for accurate measurements of temperature in turbid solutions.…”

“…Temperature-induced changes in the optical properties of Intralipid have been described previously. Kakuta et al 2 reported the temperature dependence of absorbance at 1440 nm using a spectrophotometer and proposed a method to measure the temperature of turbid aqueous solutions, but they did not recover the absorption coefficient. McGlone et al 5 determined the temperature dependence of absorption and reduced scattering coefficients of Intralipid using continuous wave photon migration measurements from 700 to 1000 nm.…”

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

“…The authors have been studying a convenient non-contact way of using near-infrared spectroscopy (NIRS) for measuring the temperature of aqueous solutions [21][22][23]. This method is based on the temperature dependence of the near-infrared (NIR) absorption of water.…”

“…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].…”

Thermal Monitoring: Raman Spectrometer System for Remote Measurement of Cellular Temperature on a Microscopic Scale

“…microscopic scale was demonstrated recently [2], [3]. This technique uses the spectroscopic measurement of the near-IR stretching band of water [4], which changes both its absorption amplitude and shape as a function of temperature.…”