TESTING 19
Micellar water characterisation via laser light scattering
n Dana Castro – Brookhaven Instruments, US
A popular facial cleanser on the cosmetic market right now is micellar water. Many companies carry this product and tout its ability to remove dirt, oil, and makeup while not irritating skin. As seen in Figure 1, micellar water is applied to a cotton pad and then wiped across facial skin to remove impurities. The main ingredients of the commercial cleanser are water, surfactant, and moisturiser, with fragrance often added.
When an aqueous solution has a certain amount of surfactant molecules, micelles are formed. The hydrophilic heads of the surfactant molecules orient themselves toward the water molecules while the hydrophobic tails orient towards each other, avoiding contact with water. These spherical aggregates are widely used in drug delivery, cosmetics, water treatment, detergents, and more. Characterisation of these micelles can help qualify their performance. One common way of
MICELLAR WATER ON COTTON WOOL
labmuffin Abstract
Micellar waters are the trendy new facial cleanser that boasts its ability to clean skin without irritation. We present results from dynamic light scattering (DLS), phase analysis light scattering (PALS), and microrheology measurements of commercial micellar water formulations using the Brookhaven Instruments NanoBrook Omni system. The size and charge of the micelles may impact their performance and stability. This technology may provide a new way to easily characterise these formulations
characterising solutions like these is using non-invasive laser light scattering. This technique can be used to measure particle size, charge, and rheological properties. Currently, it is not clear whether a qualification or characterisation method of micellar water formulations has been established. The presence of micelles and the solution’s dilute nature makes it a candidate for characterisation by laser light scattering.
In this article, four commercial micellar water formulations and one control
formulation were measured by DLS, PALS, and microrheology and typical results are presented.
Materials and method Four commercial formulations of micellar water were obtained from a local retailer (Samples 1-4). One formulation was prepared with the three main ingredients of micellar water to serve as a control (Sample 5).2
All five formulations were poured
directly into standard cuvettes for measurement.
Analysis was performed using a
NanoBrook Omni using dynamic light scattering (DLS) for particle size analysis, phase analysis light scattering (PALS) for zeta potential analysis, and microrheology for viscoelastic analysis, with the Particle Solutions software suite. Three DLS measurements, five PALS measurements, and three microrheology measurements of each sample were made to ensure repeatability and reliability of results.
micellar water
Results DLS
Layer of lipophilic
tails ready to dissolve oil and makeup
Cotton wool (hydrophilic) Figure 1: Micellar water behaviour.1 June 2018
A baseline was established with preliminary measurements at the 90° angle and 5 µs first delay time. The measurement conditions were then improved by using the backscatter angle (173°) and 0.5 µs first delay time to be able to fully interpret particle sizes below 20 nm. The correlation function is the first graph to examine when interpreting the integrity of a DLS measurement. The decay should be smooth and flatten out to a zero slope. The presence of multiple decays in a correlation function confirms the presence of multiple size populations. As seen in Figure 2, all of
PERSONAL CARE EUROPE
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