Abstract
A near-infrared absorption based laser sensor has been designed and validated for the real-time measurement of polyethylene glycol (PEG) concentration. The wavelength was selected after the determination of the absorption spectrum of deionised water and PEG solutions using a Varian Cary 6000i spectrophotometer, in order to limit the influence of PEG molecular mass on the absorption measurement. With this new sensor, the water is treated as the attenuating species and the addition of PEG in water reduces the absorbance of the medium. The concept was validated using three different PEG types (PEG 6000, 20,000, and 35,000) and it was found that the results follow Beer Lambert’s law. The influence of temperature was assessed by testing the PEG 20,000 at four different temperatures that could be encountered in a laboratory environment. The data show a slight temperature influence (increase of absorbance by 8% when the temperature rises from about 20° to about 29°). Following the validation phase conducted ex situ, a prototype of an immersible sensor was built and calibrated for in situ measurements.
Highlights
Polyethylene glycol (PEG) is a water-soluble polymer of chemical formula C2n H4n+2 On+1 that is widely used in medical, biomedical, environmental and engineering applications
The simplest method to infer PEG concentration relies on the measurement of the refractive index of the PEG solution, a method that was proposed by Lagerweff et al [2]
The equilibrium is reached after a few minutes and it can be noted that the absorbance decreases as the PEG concentration increases
Summary
Polyethylene glycol (PEG) is a water-soluble polymer of chemical formula C2n H4n+2 On+1 that is widely used in medical, biomedical, environmental and engineering applications. Polyethylene glycol has been deployed as a medium for dissolved oxygen concentration measurement [2], humidity sensors, and chronic glucose monitoring in vivo [3]. Cheng et al [7] recently provided a review of the various techniques possible to measure PEG concentration. All of these methods require advanced equipment and are not suited for continuous monitoring of PEG concentrations. The simplest method to infer PEG concentration relies on the measurement of the refractive index of the PEG solution, a method that was proposed by Lagerweff et al [2]. The method is simple, accurate equipment to measure the refractive index can be quite costly
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