Sample Preparation of Cosmetic Products for the Determination of Heavy Metals

Abstract

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.

Quality Evaluation: An Enrichment and Extension on the Experiment of Facial Toner Preparation

“…The amounts of lead and cadmium were determined by atomic absorption spectrometry, and mercury and arsenic were detected by atomic fluorescence spectrometry. − Notably, all of the large-scale instruments in the university are opened to students through teaching reform and carry out the executive procedure of sending samples for testing. About 0.5 g of sample is enough to detect the heavy metals present in the sample.…”

Critical Review on Metal‐Based Cosmetic Products

“…Wet digestion, chelation solvent extraction, dry digestion, and solid phase microextraction are the techniques that are most effective. [35] Methodologies for the Preparation…”

Health Risk Assessment of Some Heavy Metals in Lipsticks Sold in Local Markets in Iraq

“…Acids play a key role in the digestion of cosmetic samples, especially HNO3, which is used alone or with other acids. The main function of these acids is as oxidizing agents by which inorganic metal oxides can be dissolved in cosmetic samples (62). The preparation of solutions containing a mixture of concentrated acids HClO4:HNO3 of different proportions (1:1,1:2, 1:3,1:4, 2:1,3:1, and 4:1).…”