Skin care formulations have evolved as the interaction of health and beauty products for the skin. Their benefits are based on the combination of cosmetic active ingredients and targeted application. Cosmetic actives have been used in novel formulations for decades (sunscreens, anti-aging treatments, etc.), but the problems with their low solubility, low penetration, and physicochemical instability when applied to the skin have yet to be solved. One way to circumvent these shortcomings is to use lipid carriers, which are known to play an important role in the solubility of poorly soluble compounds by facilitating skin permeation and improving stability. This review addresses recent advances in skin care products that use novel nanotechnology-based lipid systems (liposomes, solid lipid nanoparticles, etc.) to deliver moisturizing cosmetic actives and improve product efficacy.

The sample preparation of a cosmetic specimen in Cosmetic Science for the purpose of determining the analytical composition of heavy and toxic metals such as lead (Pb), mercury (Hg), cadmium (Cd), and arsenic (As) is of particular importance due to the difficulty of handling the sample. There are two main methods of sample preparation. The first method is the wet digestion of the sample with strong acids such as H₂SO₄, HNO₃, HF, and HNO₃/HCl (1:3) and the combination of a strong acid with H₂O₂. Liquid digestion of the sample under the influence of strong acids damages the organic material of the sample and converts the carbon into carbon dioxide. The contained metals are oxidized to the highest oxidizing step and converted to soluble salts. A problem with this method is the loss of metals during digestion because it occurs at high temperatures as well as the decrease in the concentration of the residual acid. The second method of preparation is the wet liquid digestion of the sample with strong acids in a microwave oven in a closed vessel. The acids that are used are mainly HNO₃ or mixtures of acids such as HNO₃–HCl and HNO₃–H₂SO₄. When the sample in the acid’s solvent is exposed to microwave energy, it can reach temperatures substantially above the boiling temperature of the acid solution. The result is the decomposition of the organic material, the oxidation of the metals, and their conversion to soluble nitrates. The advantages of using microwaves are the ability to control the temperature, pressure, and loss of metals and, thus, avoid erroneous measurement results. Simultaneously with the above, extraction methods have been, for almost a decade, very effective complementary processes that we can use to enrich a sample of a cosmetic product. Liquid–liquid dispersion micro-extraction (DLLME) and solid phase extraction (SPE) are the two main methods used in sample preparation and are usually applied after the digestion process.