Abstract
The equation of state of colloids plays an important role in the modelling and comprehension of industrial processes, defining the working conditions of processes such as drying, filtration, and mixing. The determination of the equation is based on the solvent equilibration, by dialysis, between the colloidal suspension and a reservoir with a known osmotic pressure. In this paper, we propose a novel microfluidic approach to determine the equation of state of a lysozyme solution. Monodispersed droplets of lysozyme were generated in the bulk of a continuous 1-decanol phase using a flow-focusing microfluidic geometry. In this multiphasic system and in the working operation conditions, the droplets can be considered to act as a permeable membrane system. A water mass transfer flow occurs by molecule continuous diffusion in the surrounding 1-decanol phase until a thermodynamic equilibrium is reached in a few seconds to minutes, in contrast with the standard osmotic pressure measurements. By changing the water saturation of the continuous phase, the equation of state of lysozyme in solution was determined through the relation of the osmotic pressure between protein molecules and the volume fraction of protein inside the droplets. The obtained equation shows good agreement with other standard approaches reported in the literature.
Highlights
The use of microfluidic systems to study the dissolution of droplets has been sparsely investigated in the literature
Droplet dehydration was monitored at various initial saturation fractions of 1-decanol, and the equation of state of lysozyme in solution was determined through the relation of the osmotic pressure between protein of water molecules into the unsaturated continuous phase) was monitored at various initial saturation fractions of 1-decanol, and the equation of state of lysozyme in solution was determined through the relation of the osmotic pressure between protein molecules and the volume fraction of protein inside the droplets
The results indicated that the microfluidic system was a versatile tool to provide near-ideal conditions for the dehydration process
Summary
A common approach to determining this thermodynamic property of multiphasic systems is based on the equilibration by solvent exchange through a dialysis membrane, between the dispersion understudy and a reservoir with a given osmotic pressure (or water activity for the case of water). This technique has been used to study the behavior of casein [1,2,3], lysozyme [4,5], and ovalbumin [6] under compression. The application of this technique is hampered by the large sample volumes required for the dialysis chamber and by the permeation flux through the membranes
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