A refractometry-based glucose analysis of body fluids

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Clinical Diagnostics

Background:

• Refractometry offers a potential method for measuring glucose in body fluids, but requires specific conditions due to the non-specific nature of refractive index.
• Disturbing components like cells and macromolecules in biological samples must be removed for accurate refractometry.
• Tonicity, influenced by osmotically active solutes, also affects measurements and can be indirectly assessed.

Purpose of the Study:

• To determine glucose content in human blood serum derivatives using refractometry as a model for interstitial fluid.
• To establish a method combining refractive index and electrical conductivity for accurate glucose measurement.
• To evaluate the accuracy and potential error of this novel measurement approach.

Main Methods:

• Human blood serum samples were ultrafiltrated using filters with varying pore sizes (separation limits 3–30 kDa) to remove interfering substances.
• Electrical conductivity was measured to assess the tonicity (osmolality) of the samples.
• A two-dimensional calibration matrix was developed using refractive index and electrical conductivity for glucose quantification.

Main Results:

• Ultrafiltration with pore sizes between 3 and 30 kDa maximally reduced refractive index, indicating effective removal of disturbing macromolecules.
• Electrical conductivity was found to be directly proportional to osmolality, serving as a reliable indicator of tonicity.
• The developed method demonstrated a linear association with a reference method for blood glucose measurement, with deviations under 10%.

Conclusions:

• Combining refractometry and electrical conductivity measurements provides a viable method for quantifying glucose in ultrafiltrated human blood serum.
• The method shows promising accuracy for blood glucose assessment, with potential measurement uncertainties up to 20%.
• This approach offers a potential non-specific, yet accurate, method for glucose monitoring in biological fluids.