Alfatestlab is equipped with a full range of scientific instruments to analyse and optimize cosmetic formulations, in powder or liquid form, creams, gels, suspensions containing un-dissolved solids, emulsions, etc. for various applications: skin care, hair care, lotions, toothpastes, soaps, sunscreens, make-up products such as lipsticks, face powders, nail polishes etc.
To answer the growing requests from customers, cosmetic industry has to innovate, new products are being released every year from all-over the world, but to guarantee the customer satisfaction and safety an accurate characterization of raw materials and final formulations is necessary. Materials characterization prevents from issues during product lifetime, such as colour and texture variations, precipitation or creaming destabilizations, regulatory issues or customer complaints, etc.
Alfatestlab can provide analytical support to your R&D and QC teams, by controlling a large number of physical parameters on raw materials, intermediate or final formulations. We can investigate:
- Physical and thermal stability
- Spreadability and texture
- Viscosity and viscoelasticity
- Particle size and shape
- Nanomaterials content
- Perfume and odour
- Packaging impact on perfume
- Hygroscopicity
- Compaction of powders
- Density
- Flowability of powders
- Crystal and amorphous content
- Etc.
To optimize the stability of your liquid formulations we rely on the Microfluidics technology to reduce particle size of emulsions, liposomal formulations, suspensions, etc. Finally we can support you for benchmarking studies or demonstration of counterfeit products, using the physical characterization parameters to guide your steps! Here below we report some NON EXHAUSTIVE examples that illustrate our services:
Potassium Persulfate powder size analysis
Ammonium Persulfate, Potassium Persulfate and Sodium Persulfate help to decolorize or lighten hair by oxidation of the pigment molecules. To control raw material batches from 3 different suppliers, a customer asked us to measure the particle size distribution, using laser diffraction.
Figure 1 reports the particle size distribution graph and the particle size parameters table. Potassium persulfate from supplier 2 is drastically different respect to batches from the other 2 suppliers that are quite similar. Raw material from supplier 2 shows a Dv50 of 243 microns, almost 5 times larger than raw materials from the other suppliers. Particles up to 600 microns are present in the sample, that surely generate lower dissolution rate and different behaviour of the final hair bleaching product.
Figure 1. Volume particle size distribution of 3 batches of Potassium Persulfate distributed by three different suppliers.
Development of a quality control method to assess the conformity of fragrance batches.
Four batches of perfume, including the reference, were analyzed using the electronic nose technology. Characterization of odor differences between batches was carried out by investigating the chemical composition of volatile compounds. Analyses were performed in triplicate, the green line in figure 2 represents the acceptability range of the quality of the fragrance batches obtained from the analysis of the reference . Samples showing values out of the green line are considered out of specification and are rejected. The e-nose analysis allows a quick and easy quality control process of the fragrance batches. Comparing the chromatograms and Kovats indexes on the 2 columns of the electronic nose (Figure 3) it has been possible to identify limonene as the compound differentiating the investigated batches from the reference.
Figure 2. Quality Control chart of the 4 fragrance batches.
Figure 3. Chromatogram of peaks as a function of their Kovats index on the 2 columns of the electronic nose (left) and table of volatile compounds identified using the AroChemBase library (right).
Stability analysis of eye patches hydrogel
A new hydrogel for eye patch application was analysed against a reference using Mutiple Light Scattering. The technique measures the backscattered and transmitted light across the height of the sample vial. In this example we observed a change in the delta-transmission signal in the middle part of the vial compared with the reference sample, which has been attributed to a flocculation of the formulation. Phase separation was then observed in the long run, revealing the predictive value of the Multiple Light Scattering measurement. The destabilization kinetics of the samples can also be illustrated by plotting the global Stability Index over time (Figure 5), giving a clear evidence of the difference between reference and the new sample.
Figure 4. The graphs show the evolution of the delta-transmission signal as a function of tube height for the reference sample (top) and the test sample (bottom)
Figure 5. The graph shows the evolution of the global TSI (along the entire sample height) for the 2 samples analyzed. The histogram reports the TSI values at 36 hours.
Blush powder flow and compaction properties
In this example two different face blushes were characterized using powder rheology. The products both consist of two natural mica pigments (Bronze and Orange), which on sensory analysis show opposite behaviour: the product containing the bronze pigment has very good writability and medium hardness, while the bright orange pigment has medium writability and was too compact. The two pigments were characterized in terms of particle size and absorption showing comparable results. Rheological characterization highlighted the difference between the two powder samples that emerged from the sensory analysis.
In the compressibility test shown in figure 6, the Orange sample shows a higher compressibility percentage (CPS) versus applied normal force than sample Bronze, indicating a higher change in volume upon compression value and a lowest bulk density value (CBD), indicating a less efficient packing of the powder with greater presence of gaps between particles.
Figure 7 shows the shear stress required to induce powder movement following consolidation by applying different values of normal force. Orange sample shows a higher Cohesion and Unconfined Yield Strength (UYS) values than sample Bronze, indicating that more stress is required to break the consolidated structure and induce movement, i.e., the powder remains more compact upon stress.A too compact powder may not work properly for some cosmetic products such as face blushes.
Figure 6. The graph shows the compressibility % versus applied normal force and the parameters of Bulk Density (CBD) and Compressibility (CPS%) in the table.
Figure 7. The graph shows the shear stress as a function of the applied normal force and the parameters of Cohesion (C) and Unconfined Yield Strength (UYS).
Rheology of hyaluronic acid solutions and gels
The investigation of the rheology of hyaluronic acid solutions and gels is useful for many crucial aspects of these products, such as their handling and injection. A key role is played by the viscoelastic properties, that describe in which circumstances is dominant the solid-like (elastic) behavior or the liquid-like (viscous) one.
In the Figure 8 is reported the result of the oscillation frequency sweep test performed on two different formulations, a crosslinked hyaluronic acid formulation and a linear one.
The crosslinked product shows throughout the frequency range a predominant elastic behavior, where the storage modulus G’ is higher than the loss modulus G’’, a typical outcome of a dermal filler. On the other hand, the linear formulation is dependent on the oscillation frequency applied: at low frequency a viscous behavior prevails, characteristic of an ophthalmic lubricant.
Figure 8. Oscillatory frequency sweep performed on a crosslinked hyaluronic acid formulation (* symbol) and a linear one (○ symbol). The storage modulus G’ profile (red line) and the loss modulus G’’ profile (blue line) are reported for each sample.
Thixotropy of body moisturizers
The behavior of many personal care products, that flows when squeezed out of the tube and then recover to their initial state to remain in place, can be assessed with a structure and recovery rheological test. This property, named thixotropy, is time dependent, as shown in Figure 9. In the first step is evaluated the behavior of the product at rest, then a structural decomposition is induced and finally the structural regeneration is evaluated. In the example reported in Figure 9, four body moisturizers were compared: the Body Milk A shows the lower relative recovery, respect to the other three products tested.
Figure 9 – Structure and recovery test. Comparison of Body Milk A (red line), Body Milk B (blue line), Body Lotion C (Orange) and Body Lotion D (Green).
