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Antimicrobial agents are added to a wide variety of products such as cosmetics to reduce the risk of microbial contamination and ensure the suitability and safety of the product. However, recent studies have shown that these compounds can have negative effects on human health and the environment. Therefore, it is crucial to develop analytical methods to control the amount of these compounds in personal care products to guarantee human health and product quality. This paper presents an HPLC method with electrochemical detection using a gold electrode for the determination of the most used antimicrobial agents in cosmetic products: methylparaben (MP), 4-hydroxybenzoic acid (4-HBA), phenoxyethanol (PE) and methylisothiazolinone (MIT). For this purpose, the electrochemical response of these compounds was evaluated on the gold electrode. The optimal electrochemical detection of MP, 4-HBA; PE and MIT was performed at pH 2 and + 1.50 V (vs Ag/AgCl). Under the optimal separation and detection conditions, limits of detection (LODs) between 10 and 110 μg L− 1 were obtained. These LODs are lower than those previously reported for other HPLC methods with mass spectrometry and diode-array detectors. Cosmetic products with different compositions were successfully analysed with the proposed HPLC method obtaining recoveries between 76 % and 119 %, Lucía Abad thanks to Universidad Autonoma ´ de Madrid for the predoctoral fellowship (FPI-UAM program). Sergio Lucas-Sanchez ´ acknowledges to Comunidad de Madrid and European Social Fund for the contracts PEJ-2018-AI/BIO-11845 through the Youth Employment Initiative (YEI)

Resumen del póster presentado al 9th Euro-Mediterranean Symposium on LIBS and Colloquium Spectroscopicum Internationale XL, celebrado en Pisa (Italia) del 11 al 16 de junio de 2017., Silicon is not considered nowadays as an essential element for humans, but it is suspected that this metalloid plays a key role in the development of bones, cartilage and other connective tissues. In addition, recent findings provide that silicon may have a modulating effect on the immune and inflammatory response, and has been associated with mental health. Due to these benefits, silicon is used in cosmetic and pharmaceutical products and to prepare functional foods. Silicon incorporation in these products is often performed in emulsions or double emulsions. Oil-in-water multiple emulsions are complex liquid dispersions employed to entrap, protect and control the release of different substances such as minerals. The development and implementation of analytical methodologies that allow the accurate and precise quantification of silicon is of great interest for laboratories devoted to routine analysis. However, silicon determination is considered to be one of the most challenging tasks in elemental analysis. This is partially due to the high risk of sample contamination owing to the ubiquity of this element and the possible loss of this analyte during the sample pretreatment process owing to the high volatility of some silicon compounds. In this context, the development of analytical methodologies based on direct analysis of the sample are considered very interesting approaches to determine silicon compared to traditional methods based on wet digestion of the samples. As additional benefits, these analytical strategies are simple and increase the speed of analysis. Highresolution continuum source atomic absorption spectromety with flame atomizer (HR-CS FAAS) improves the possibilities for the development of direct methods. HR-CS FAAS allows the detection and correction of spectral interferences from the matrix sample as well as carry out an automatically and truly simultaneous background correction for continuous events which leads to more stable baselines. Moreover, due to the high resolution (a few picometers per pixel) provided by HR-CS FAAS instrument, it is possible to separate the absorption signal of silicon at 251.611 from the one at 251.432 nm that is typically a problem using traditional AAS. This work presents the development of a fast and straightfonvard method based on HR-CS FAAS for the determination of silicon in difierent oil-in-water emulsions. To achieve this purpose, the main analytical line of silicon at 251.612 nm was select, and the burner height and flame composition were optimized. The feasibility to perform the calibration with aqueous standards was evaluated and the principal analytical parameters were calculated. Finally, the proposed analytical approach was applied to determine this metalloid in different oil-in-water emulsions.