HPLC method with electrochemical detection on gold electrode for simultaneous determination of different antimicrobial agents in cosmetics

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

A MWCNTs-COOH/PSS nanocomposite–modified screen-printed electrode for the determination of synthetic phenolic antioxidants by HPLC with amperometric detection

New sensing platforms based on screen-printed carbon electrodes modifed with composites based on polystyrene sulfonate and oxidized multi-walled carbon nanotubes (PSS/MWCNTs-COOH/SPCE) have been used to develop a novel HPLC method with electrochemical detection (ECD) for the determination of the most used synthetic phenolic antioxidants in cosmetics: butylhydroxytoluene (BHT), butylhydroxyanisole (BHA), tert-butylhydroquinone (TBHQ) and propyl gallate (PG). Optimal separation conditions were achieved using methanol: 0.10 mol L−1 acetate solution at pH 6 as mobile phase with a gradient elution program from 60 to 90% of methanol percentage in 15 min. The electrochemical detection was carried out in amperometric mode using the PSS/MWCNTs-COOH/SPCE at+0.80 V vs. Ag. Under these optimal separation and detection conditions, the limits of detection (LOD) were between 0.11 and 0.25 mg L−1. These LOD values were better, especially for BHT, than those previously published in other HPLC methods. Linear ranges from 0.37 mg L−1, 0.83 mg L−1, 0.69 mg L−1 and 0.56 mg L−1 to 10 mg L−1 were obtained for PG, TBHQ, BHA and BHT, respectively. RSD values equal or lower than 5% and 8% were achieved for repeatability and reproducibility, respectively. The HPLC-ECD method was successfully applied to analyze diferent cosmetic samples. Recovery values within 83–109% were obtained in the validation studiesOpen Access funding provided thanks to the CRUE-CSIC agreement with Springer Natur

Disposable screen-printed carbon-based electrodes in amperometric detection for simultaneous determination of parabens in complex-matrix personal care products by HPLC

Parabens are chemicals widely used as preservatives in different types of industrial products. In recent years, the concern about the safety of these compounds has increased due to their endocrine disrupting activity. For this reason, their use is highly regulated and even some of them have already been banned. Thus, methods for the sensitive and selective detection of these compounds are required to control their presence in food, cosmetic, and pharmaceutical products. This paper presents an HPLC method with electrochemical detection using disposable screen-printed electrodes (SPE) for simultaneous determination of 6 different parabens in personal care products. Electrochemical behaviour of parabens was studied on SPE with different carbon-based materials as working electrode: carbon, ordered mesoporous carbon and graphene. From these studies, pH, detection potential, and the most adequate SPE were chosen. Due to the wide range of textures and viscosities (e.g., liquid, solid, and semi-solid) of personal care products, adequate sample pretreatments are required before chromatographic measurement. Here, a fast ultrasound-assisted extraction method was applied to simultaneously extract 6 parabens (methyl-, ethyl-, isopropyl-, propyl-, butyl-and benzyl-paraben) from different complex-matrix cosmetic products. Instrumental limits of detection between 20 and 115 μg L− 1 were obtained applying +1.0 V (vs. Ag) as detection potential on carbon-based SPE. The total analysis time, including sample extraction and HPLC run, was shorter than 35 min. The proposed method is more versatile and faster than the current available methods and has been successfully applied to determine parabens in commercial samples such as shampoos, body creams, facial tonics, and toothpastesLucia Abad acknowledges to Universidad Autonoma de Madrid for the predoctoral fellowship (FPI-UAM program). Sergio Lucas and Carmen Isabel thanks to Community of Madrid and European Social Fund for the contracts PEJ-2018-AI/BIO-11845 and PEJ-2019-TL/IND-14286, respectively through the Youth Employment Initiative (YEI

Direct determination of silicon in oil-in-water emulsins by high-resolution continuum source flame atomic absorption spectromtry

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.Peer Reviewe

A slurry sampling high resolution continuum source graphite furnace atomic absorption spectrometry approach to determine metals in biomass bottom ash

Industrial by-products such as biomass bottom ash (BBA) should be reused in the context of the Circular Economy, but their use depends on the content of major, minor, and toxic elements. In this work, a slurry sampling method based on High Resolution Continuum Source Graphite Furnace Atomic Absorption Spectroscopy (HR-CS GFAAS) was developed for the determination of Pb, Cu, and Fe in these by-products. Using a two-step multivariate experimental design, the optimal conditions for the preparation of the sample suspensions (dispersion of 10.0 mg of 32 µm sieved BBA sample in 10.0 mL of 1.4% (v/v) HNO3 and 0.7% (v/v) Triton X-100 solution using an ultrasonic bath for 1.0 min (50% power; 80 kHz)) were established. The GFAAS temperature program was optimized using both aqueous standards and BBA slurries, allowing the determination of the three metals in a single analytical run and with the same sample aliquot. Under the optimal conditions the limits of detection (LODs) were 0.55 µg g−1, 0.21 µg g−1, and 0.72 mg g −1 for Pb, Cu, and Fe, respectively. Different BBA samples were analyzed using the proposed method. The suitability of the method was probed by determining the concentrations of the metals in the solutions obtained after microwave acid digestion of the BBA samples, obtaining statistically comparable results (Student-t test for two independent samples at a 95% confidence level)

Straightforward silicon determination in water-in-oil-in-water emulsions used for silicon supplementations in food by high-resolution continuum source flame atomic absorption spectrometry

Water-in-oil-in-water (W/O/W) double emulsions are complex liquid dispersions employed to entrap, protect and control the release of different substances such as minerals in cosmetics, pharmaceuticals, and food. The present paper proposes a simple and fast analytical procedure for silicon determination in double emulsion samples formulated for the supplementation of silicon in different food products. Silicon determination was performed by flame atomic absorption spectrometry (FAAS) at the main analytical line (251.611 nm) using a high-resolution continuum source instrument. The introduction of the sample in the spectrometer in a continuous or discontinuous mode and the influence of double emulsion matrix on silicon absorbance signals were investigated. At the optimized conditions, the double emulsion samples were analysed using silicon standards in ultrapure water for calibration. The limits of detection (LODs) were 0.04 and 0.11 mg L and the upper limits of silicon linear working ranges were up to 23 and 70 mg L for continuous and discontinuous sample introduction modes, respectively. Silicon spiked double emulsion samples were analysed for validation purposes. The good recoveries (within 95–105%) demonstrated the suitability of the proposed method.Peer Reviewe

Physicochemical properties and encapsulation of silicon in double emulsions for healthier food applications

This article analyses the potential use of double emulsions as silicon delivery systems with reference to the influence of the composition of the inner aqueous phase (W, containing NaCl and sodium caseinate or gelatin) on silicon encapsulation and physicochemical properties of food-grade W/O/W. Irrespective of W, DEs initially showed a well-defined monomodal distribution, with the widest range registering in the sample with gelatin. All samples developed a bimodal distribution during storage (3 ± 2 °C). Heating increased the range of droplet size distribution. DEs exhibited high physical stability (creaming), decreasing over storage; this behaviour was generally unaffected by W composition, which maintained similar stability (95–96%) at the end of storage. Viscosity was generally unaffected by formulation, storage time or heating treatment. Si encapsulation efficiency (72.4 and 78.3%) was not affected by W composition, while Si encapsulation stability was generally unaffected by either storage or heating. These DEs can be used as potential ingredient (with lower fat content, better fatty acid profile and with the potential Si health benefits) for the development of healthier foods including meat products.This research has been supported by Project AGL 2011-29644-C02-01 and AGL2014-53207-C2-1-R from the Spanish Ministry of Science and Innovation.Peer Reviewe