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Servolab Science News N°3: Powder Composition

ABSTRACT

Commercial talcum powders for the skin are cosmetic products that are generally made with mineral talc, a silicate with the formula 3MgO-4SiO2·H2O. International regulations establish special compositions for these products to consider them for commercial use, outside of these ranges the powder is considered for industrial use. The objective of this work was to evaluate the composition of some commercial talcs available in regular stores by X-ray techniques. Five brands were selected that included baby talcs and foot talcs, four of them talc-based and one cornstarch-based, whose origins are China, India and Venezuela. The mineral phases present in these products were identified and quantified by X-ray diffraction (XRD); while the elemental chemical composition was evaluated by X-ray fluorescence (XRF). The results obtained reveal that, of the five brands evaluated, three of them do not meet the conditions to be considered commercial powders for use in humans, showing compositions that differ from those indicated on the product labels. Of these three brands, one of them does not contain talc, despite being indicated on the product and its composition is based on carbonaceous compounds (calcite, aragonite and dolomite); while the other two contain dolomite as the majority component. Only the product from Venezuela (talc-based) and the one from India (cornstarch-based) meet the specifications indicated by the manufacturers. Products that do not comply with the indicated formulations can be considered industrial grade products due to their composition.

Key words: Talc, X-ray, diffraction, fluorescence.

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