Diffusiometry

Diffusiometry is a technique used to measure diffusion coefficients of molecules in a solution. Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, driven by random thermal motion. The diffusion coefficient quantifies how quickly this movement occurs. Diffusiometry experiments typically involve creating a concentration gradient and monitoring its evolution over time.

Several methods fall under the umbrella of diffusiometry. Interferometric diffusiometry is a common approach that utilizes optical interferometry to detect and quantify the refractive index changes associated with the concentration gradient. As molecules diffuse and the concentration profile changes, the interference pattern of light passing through the sample is altered, allowing for the calculation of the diffusion coefficient. Other techniques include conductometric diffusiometry, which measures changes in electrical conductivity, and refractometric diffusiometry using refractometers.

The measured diffusion coefficient is influenced by various factors, including the size and shape of the diffusing molecules, the viscosity of the solvent, and the temperature. Diffusiometry finds applications in diverse fields such as polymer science, where it is used to determine molecular weights and polydispersity, and in biochemistry, for studying protein-ligand interactions and protein aggregation. It is a valuable tool for characterizing the behavior of molecules in solution and understanding transport phenomena.