Real-time compensation method for robust polarimetric determination of glucose in turbid media

Abstract

Polarimetric determination of glucose is known to be strongly affected by scattering in turbid media. Other effects like fluctuations of light source emission and sample absorption also deteriorate glucose predictability. This work presents a measurement setup using a real-time data processing method to address these problems. The approach uses the frequency-dependent intensity components created when the polarization of the incident light is periodically modulated by a Faraday rotator. The efficacy of the proposed method was verified experimentally for a glucose range of 0 − 500 mg/dl. It was shown that the approach reduces the prediction errors in slightly turbid media from 35.7 mg/dl down to 1.17 mg/dl. In a similar way, the glucose predictability for fluctuating light source emission was improved from ±16.16 mg/dl to ±1 mg/dl and for varying sample absorbance from ±15.69 mg/dl to ±1.23 mg/dl, respectively. Therefore, considerable improvement of robustness and reproducibility of glucose determination was demonstrated.

Broadband polarimetric glucose determination in protein containing media using characteristic optical rotatory dispersion

“…• T As demonstrated in a previous work [27], all frequency components in Eq. 3are proportional to the absolute light intensity.…”

“…Based on the sinusoidal Faraday modulation at frequency ω, the detected signal has to be processed to obtain its respective frequency components. The resulting signal consists of three frequency components [23,27]. One DC-part, one at the modulation frequency ω and the last at the double frequency 2ω.…”

“…Using the ratio of Eq. (4) influences of the light source intensity, sample absorbance and slight scattering are greatly reduced, improving the reproducibility and robustness of polarimeter-setups without the need of additional hardware or reference measurements [27]. Therefore, this method was used in the present work.…”

“…With the goal of a long-term stable and robust polarimetry for medical applications, we already demonstrated that our setup is able to measure independent from fluctuations in absolute light intensity and slight scattering effects [27]. Since the spectral ORD overlap of glucose with other substances remains a major source of error, we present a broadband polarimeter setup, similar to the system proposed by Cote et al [28].…”

Review of Non-Invasive Glucose Sensing Techniques: Optical, Electrical and Breath Acetone

“…Mukherjee et al developed Mueller matrix polarimeter with measurement precision of 0.004 • and 0.0004 in optical rotation and depolarization, respectively, and achieved glucose detection sensitivity as low as 20 mg/dL [85]. Another approach to reducing glucose prediction error caused by scattering in slightly turbid media (with scattering coefficient of 0.225-0.275 cm −1 ) is using the Faraday-modulated polarimeter set up and measuring the ratio of light intensity at two specific frequencies [87].…”