Method for non-invasive concentration measurement in polymer mixtures: tests with dextran and cytochrome-c

摘要

Background Non-invasive measurement of solute concentratons in a binary macromolecule system is a powerful tool for the study of mass transport phenomena, particularly for studying solute-solute interactions. our objective is to extend an existing differential refractometric technique for measurement of concentrations in a two-macromolecule system.Methods Weused a specially designed cell and associated optical equipment to measure thhe local refractive index and light extension coefficient of a polymer mixture. The macromolecules used were dextran (molecular weight 2 million) and the protein cytochrome-c. A three-layered calibration procedure quantified the refraction and light extinction due to each of these components in a mixture, as well as the interaction between the two components.Results Calibration data showed that dextran and cytochrome-c concentrations could be determined from mixture properties with good accuracy and repeatability. Secifically, for cytochrome-c over the concentraton range from 0.1-0.6 mass%, the maximum uncertainty in measured concentration was approximately +-0.013%, expressed as a 955 confidence interval for the measurement. The corresponding maximum uncertainty for detran over the concentration range from 0.1-0.6 mass% was +-0.037%.Conclusion The experimental approach proposed herein is suitable fot he measurement of transport in binary polymer mixtures where one or both components are fairly strongly light-absorbing. It allows real-time monitoring of macromolecular transport without radioactive trcers or other complex equipment.