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Emulsion characterization by the combined sedimentation field—flow fractionation—photon correlation spectroscopy methods

1989; Elsevier BV; Volume: 132; Issue: 1 Linguagem: Inglês

10.1016/0021-9797(89)90235-x

1095-7103

Karin D. Caldwell, Jianmin Li,

Air Quality and Health Impacts

The combination of sedimentation field-flow fractionation (sedFFF) and photon correlation spectroscopy (PCS) is shown to characterize the size distribution for polydisperse samples, where neither technique by itself is capable of producing this information. PCS, on the one hand, gives accurate diameter assignments for monodisperse suspensions but fails to describe the size composition of mixed samples. sedFFF, on the other hand, is a high-resolution separation technique that is capable of yielding detailed size information, provided the particle density is accurately known. Where this is not the case, the technique fails to evaluate the fractogram in terms of a size distribution. By combining the two characterization methods, the well size-sorted particles that elute from the separator can be evaluated in terms of both size and density. To yield accurate readings in PCS, the particle concentration must exceed a certain critical value; in FFF, however, accuracy is promoted by reduced sample loads. The implication of these constraints for combining the two techniques is discussed, and conditions that will reduce errors in the analysis of particle sizes present in a given sample are suggested. The protocol is applied to the analysis of two emulsions (Liposyn and Hercon 85) for which density differences between particle and suspension medium are not known from outside sources. Although these differences are found to be quite small, they can be determined with sufficient accuracy to permit the evaluation of particle sizes present in the tWO emulsions.