Influence of molecular exchange on the enclosed water volume fraction of W/O/W double emulsions as determined by low-resolution NMR diffusometry and T2-relaxometry

Low-resolution T2-relaxometry and pfg-NMR diffusometry were applied for determination of the enclosed water volume fraction of liquid oil and solid fat based W/O/W emulsions. Whereas pfg-NMR diffusometry enables the discrimination between internal and external water based on differences in diffusion behavior, the T2-relaxometry method is based on the relaxation behavior differences of the internal and external water upon addition of an external water-soluble paramagnetic probe, such as manganese dichloride. Provided that data-acquisition and data-analysis were optimized to eliminate interfering effects, such as oil phase contribution, incomplete signal relaxation or exchange between the internal and external water phase, both investigated NMR methods provided similar results. As compared to most alternative techniques, low-resolution NMR does not require the physical separation of both water phases. In addition, both low-resolution NMR techniques do not require any tracer addition during multiple emulsion preparation, and hence can also be applied on existing formulations. Whereas T2 relaxation is faster and less affected by NMR parameters, pfg-NMR has the advantage that it does not require any sample pretreatment.