An investigation into the use of low-frequency dielectric spectroscopy as a means of characterizing the structure of creams based on Aqueous Cream BP.
A range of creams based on Aqueous Cream BP have been analyzed using low-frequency dielectric spectroscopy, with accompanying circuit modeling in combination with rheological and microscopic supportive techniques, to explore the use of the dielectric approach as a novel means of characterizing cream systems. Creams based on the formula for Aqueous Cream BP were produced by hand-mixing and mechanical mixing, with and without the inclusion of the preservative phenoxyethanol. Dielectric analysis was performed over a frequency range of 10(-2)-10(5) Hz. Cream samples were also examined using stress scan rheology and differential interference contrast microscopy. Dielectric analysis indicated that the presence of preservative decreased the capacitance and loss of the creams. The responses were modeled in terms of a dispersive capacitance in series with two RC circuits (series and parallel). Rheological studies indicated higher viscosities for the hand-mixed and unpreserved systems. Differential interference contrast microscopy showed marked differences in the distribution of the oil droplets, depending on the method of mixing. The study has demonstrated that dielectric spectroscopy, with accompanying circuit analysis, may be used as a means of modeling the structure of cream systems. The investigation has also shown that the formulation and preparation method of Aqueous Cream BP may have a profound effect on sample structure.
Goggin
P L
PL
the Centre for Materials Science, School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK.
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R
R
Craig
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DQ
Gregory
D P
DP
D002626:Chemistry, Pharmaceutical / Q000379:methods; D004553:Electric Conductivity; D005026:Ethylene Glycols / Q000737:chemistry; D009824:Ointments / Q000737:chemistry*; D012212:Rheology; D014867:Water
D005026:Ethylene Glycols; D009824:Ointments; D014867:Water; C005398:phenoxyethanol