Elsevier

Talanta

Volume 171, 15 August 2017, Pages 291-306
Talanta

Screening of TiO2 and Au nanoparticles in cosmetics and determination of elemental impurities by multiple techniques (DLS, SP-ICP-MS, ICP-MS and ICP-OES)

https://doi.org/10.1016/j.talanta.2017.05.002Get rights and content

Highlights

  • Sunscreens, toothpastes, shampoos, face creams and lip balm have been analyzed.

  • Screening of TiO2 nanoparticles has been performed in cosmetics.

  • DLS and SP-ICP-MS techniques have been applied and compared.

  • Elemental impurities were determined by ICP-OES and ICP-MS after sample digestion.

  • TiO2 nanoparticles were found in ‘nano’- labeled products and in one non-labeled.

Abstract

Cosmetics are part of the daily life of most of the people. Thus, a complete characterization of the products we applied in our skin is necessary. In this work, an analytical investigation of a wide variety of cosmetics from the point of view of total element content and metallic nanoparticles (NPs) has been performed. Firstly, we analyzed the total element content by ICP-MS and ICP-OES after acid digestion as an assessment of the presence of metal impurities. Prohibited elements in cosmetics, according to the European Commission regulation No 1223/2009, were not detected, and only elements mentioned in the label were found (e.g. Al, Fe, Ti and Si). Secondly, a screening of the presence of NPs has been performed by Dynamic Light Scattering (DLS) and Single Particle Inductively-Coupled Plasma Mass Spectrometry (SP-ICP-MS). Two sample preparation procedures were applied. The first protocol consisted in the preparation of suspensions in 0.1% w/v SDS and the second based on defatting with hexane followed by resuspension in water. DLS was employed as a routine method for a fast analysis of NPs, but this technique showed limitations due to the lack of specificity. SP-ICP-MS analyses were then performed, first as a screening technique to evaluate the presence of TiO2 and Au NPs in cosmetics suspensions prepared in SDS; and second, when a positive answer was obtained about the presence of NPs from the screening, SP-ICP-MS was used for particle size determination. Results showed that only TiO2 NPs were present in two sunscreens, one anti-wrinkle day cream, one lip balm protector labeled as ‘nano’ and in one brand of toothpaste not labeled as ‘nano’. Sizes obtained for both sample preparations were compared and ranged from 30 to 120 nm in most of the samples.

Introduction

Nowadays, millions of people benefit daily from the use of cosmetics and personal care products (e.g. anti-perspirants, anti-aging, anti-wrinkle, anti-dandruff, hydration, sun protection, tooth, hair and body cleaning products). Therefore, cosmetics represent a global industry, showing retail sales price in Europe of 72.5 billion € in 2014 mainly in Germany, France, UK, Italy and Spain [1].

In general, cosmetics and personal care products involve a very complex matrix with a lot of different components that fall into these categories: a) minerals (talc, kaolin, TiO2, ZnO, mica), b) vegetable powders (corn starch, rice flour), c) oils, fats and waxes (lanolin, cocoa butter, petroleum such as baby oil and Vaselin), d) dyes, pigments and colorants, e) preservatives (biocide such as thimerosal and methylparaben), e) UV filters (inorganic such as TiO2 and organics), f) others (water or other solvents, perfumes, fragrances, antioxidants, surfactants, alcohols, amines, esters, amides, plasticizers, polymers, pearls and hydroxydes) [2]. Before cosmetics commercialization, the products are submitted to a rigorous evaluation in terms of effectiveness, human safety, cytotoxicity, skin penetration and tolerance [3]. Even though, they may contain elemental impurities, from raw materials or during processing and storage, that may cause allergic and dermatological reactions [1]. For example, it is extensively well-known that Ni and other metals occurring as impurities in cosmetics might give rise to contact dermatitis in subjects with pre-existing allergy [4].

Other components that appear recently in cosmetics are in the form of nanoparticles (NPs). For example, TiO2 and ZnO in nanoform are extensively used in current sunscreens due to their high photostability and low photoallergic potential [5], [6]. In addition to being colorless, these NPs filter UV light more efficiently than microparticles [7]. The common primary size of TiO2 NPs are in the range 10–100 nm, but when applied on skin, aggregates of primary particles ranging from 30 to 150 nm in size occur [7]. It is commonly assumed that the small particles exhibit more harmful effects [8]. However, there is a certain controversy in terms of toxicity and the knowledge of potential risks at sizes below 100 nm is still insufficient [9], [10]. Some researchers considered that these NPs aggregates maintain invariable their structure once applied on the skin, prevent the release of primary particles and consequently produce negligible risks for humans [7]. In contrast, moderate opinions declared that the NPs are not totally harmless to humans and the toxic effects are conditioned by dose, size and phase composition of the particles [11]. In fact, higher cytotoxicity was observed for TiO2 NPs (3–10 nm) of anatase than rutile [12]. In addition, these products may suffer modifications during water immersion, temperature, humidity, UV radiation and abrasion with beach sand that are not considered [3]. Other authors argued that the main problem of TiO2 NPs rise from the generation of reactive oxygen species (ROS) (e.g. OH radicals) under UV irradiation [12]. For instance, the application of TiO2 NPs of 20 nm on human skin generates free radicals may destruct certain skin cells [11]. To overcome this problem, TiO2 NPs in sunscreens are generally coated with magnesium, silica, alumina or zirconium materials (and also organic compounds, such as silicone) [9], [11], [13], [14].

At the moment, the current regulation for cosmetics is published as Regulation of European Commission (EC) No 1223/2009 of 30 November 2009 starting from 11 July 2013 [15]. As it is summarized in Table 1, EC includes a list of prohibited substances, substances that must not be present, impurities, allowed colorants, preservatives and UV filters. Moreover, there is a special section for nanomaterials (NMs). According to this regulation, when NMs are present in cosmetics, the word “nano” should appear between brackets in the list of ingredients in the label of the product. In the case of cosmetics, and specifically for substances to protect the skin against certain UV radiation, TiO2 in nanoform is allowed as UV filter in sunscreens. Nevertheless, there is uncertainty on regulatory status, roles, responsibilities and practical guidance on the impact of packaging in the cosmetic product safety assessment. This problematic will be resolved by the European Commission in 2018 when it is planned to release the regulatory approach regarding NMs.

Taking into account these considerations, the chemical characterization of inorganic components of cosmetics including metal impurities and NPs is of great concern for the cosmetic industry. Total element analysis is generally performed after matrix destruction by dry ashing [16], [17] and wet digestion [18], [19], [20], [21] often assisted by microwave energy [4], [22], [23], [24]. Another faster and green alternative of sample preparation approach is for example, ultrasound-assisted emulsification [25], [26]. Detection is usually performed by Inductively-Coupled Plasma Optical Emission (ICP-OES) [26], [27], [28], [29] and Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) [4], [30].

Nevertheless, the analysis of NPs is still a challenge. Main inconveniences range from the difficulty of extraction/isolation of NPs from the matrix to the liquid media, the stabilization of NPs and the validation of the developed methodology. However, a wide range of techniques is available for the characterization of TiO2 NPs in cosmetics, including microscopy, spectroscopy and size separation techniques. Several publications have been reported for TiO2 NPs in cosmetics using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) [3], [13], [31], [32], [33], [34], [35], [36] and Flow-Field Fractionation techniques (FFF) coupled to Multi-angle Laser Light Scattering (MALLS) and ICP-MS [11], [37], [38], [39], [40]. One of the most promising techniques that provides information on particles size and distribution of a selected metallic composition is Single-Particle Inductively Coupled Plasma Mass Spectrometry (SP-ICP-MS). This technique is gaining more and more adepts, especially on a routine basis due to its rapidity of analysis and not high requirements for sample preparation [41], [42]. Until now, some studies have been published for the analysis of TiO2 NPs in cosmetics (sunscreen and toothpaste) by SP-ICP-MS [40], [43], [44]. Before analysis, sunscreens were dispersed/suspended in a surfactant solution followed by manual or vortex stirring [43], [44]. Toothpaste was however digested using H2O2 to decompose the organic matrix, the obtained solution was then evaporated and diluted in water [40].

Whereas some studies are available for trace elements and NPs analysis in cosmetics, a fast screening tool to evaluate the presence of NPs in cosmetics has not yet been proposed. The main objective of this work is to perform a complete characterization of a wide range of cosmetic products in terms of elemental impurities and NPs by developing a screening methodology. Total elemental content was achieved by spectrometric techniques (ICP-OES and ICP-MS) after acid digestion. In relation to the presence of NPs, Dynamic Light Scattering (DLS) and SP-ICP-MS were the selected techniques because of their interest in routine analysis. Indeed, DLS is a simple technique that provides a fast information about the presence of NPs and their size. As no information about the chemical composition of NPs is given, SP-ICP-MS was applied as a screening tool to obtain specific information of TiO2 and Au NPs, explaining the reasons for a positive or negative response in the screening test and to provide particle size for samples with a positive answer.

Section snippets

Instrumentation

Determination of the total element content was carried out using a Spectro Arcos ICP-OES (SPECTRO Analytical Instruments GmbH, Kleve, Germany) with side-on plasma interface (SPI) and a NexION 300X ICP-MS fitted with a Meinhard nebulizer and a cyclonic spray chamber in standard mode and with collision cell filled with He (Perkin-Elmer, Shelton, CT, USA). The ICP-OES and ICP-MS measurement conditions were daily optimized to provide the highest intensity using standard built-in software

Determination of elemental impurities in the selected cosmetic samples

Several elements or certains of their compounds prohibited in cosmetics according to the EC (see Table 1) such as As, Sb, Pb, Cd, Ni, Ag, Zr, Cr and Sr were analyzed in the 16 studied samples. Moreover, other listed elements that must be not contained except the subjected to some restrictions such as Al, Ti, Sn, Zn, Ag and Sr were also determined. Finally, other elements allowed as colorants (e.g. Al, Cr, Cu, Au and Fe), preservatives (e.g. Zn, Ag), UV filters (e.g. Ti) and NMs (TiO2 nano) or

Conclusions

Different techniques have been used in this study in order to evaluate the presence of elemental impurities as well as NPs in sixteen cosmetics commonly used. The total element analysis has shown that elements prohibited by the EC regulation were usually not present. In general, elements that appeared in the label have been found in the samples, such as Al, Fe, Ti and Si. In relation to Au, only in the expensive brands that supposedly contained Au, its quantification was possible. Thus, in this

Acknowledgement

I. de la Calle thanks Xunta de Galicia for financial support as a post-doctoral researcher of the I2C program and cofinancing by the European Social Funding P.P. 0000421S 140.08 and the UT2A/Adera for giving her the opportunity to learn and research in their research center. Authors would like to thank Dr. O. F. X. Donard and Dr. O. Baltróns (IPREM) for the assistance with the ICP-MS, D. Montaut and Dr. C. Gleyzes (UT2A/ADERA) for their help with the ICP-OES.

References (70)

  • A. Salvador et al.

    , Analytical methodologies for atomic spectrometric determination of metallic oxides in UV sunscreen creams

    (2000)
  • A. Salvador

    Determination of selenium, zinc and cadmium in antidandruff shampoos by atomic spectrometry after microwave assisted sample digestion

    Talanta

    (2000)
  • G.A. Zachariadis et al.

    Multi-element method for determination of trace elements in sunscreens by ICP-AES

    J. Pharm. Biomed. Anal.

    (2009)
  • P.-J. Lu et al.

    Analysis of titanium dioxide and zinc oxide nanoparticles in cosmetics

    J. Food Drug Anal.

    (2015)
  • C. Contado et al.

    Size characterization by sedimentation field flow fractionation of silica particles used as food additives

    Anal. Chim. Acta

    (2013)
  • Y. Dan et al.

    Rapid analysis of titanium dioxide nanoparticles in sunscreens using single particle inductively coupled plasma–mass spectrometry

    Microchem. J.

    (2015)
  • I. López-Heras et al.

    Prospects and difficulties in TiO2 nanoparticles analysis in cosmetic and food products using asymmetrical flow field-flow fractionation hyphenated to inductively coupled plasma mass spectrometry

    Talanta

    (2014)
  • V. Marassi et al.

    Hollow-fiber flow field-flow fractionation and multi-angle light scattering investigation of the size, shape and metal-release of silver nanoparticles in aqueous medium for nano-risk assessment

    J. Pharm. Biomed. Anal.

    (2015)
  • P. Krystek et al.

    Analytical assessment about the simultaneous quantification of releasable pharmaceutical relevant inorganic nanoparticles in tap water and domestic waste water

    J. Pharm. Biomed. Anal.

    (2015)
  • F. Laborda et al.

    Single particle inductively coupled plasma mass spectrometry for the analysis of inorganic engineered nanoparticles in environmental samples

    Trends Environ. Anal. Chem.

    (2016)
  • S. Liu et al.

    Effect of methanol and sodium dodecylsulfate on radial profiles of ion abundance in inductively coupled plasma mass spectrometry

    Spectrochim. Acta Part B At. Spectrosc.

    (2006)
  • Y. Zhang et al.

    Stability of commercial metal oxide nanoparticles in water

    Water Res.

    (2008)
  • T. Poiger et al.

    Occurrence of UV filter compounds from sunscreens in surface waters: regional mass balance in two Swiss lakes

    Chemosphere

    (2004)
  • N. Bendixen et al.

    Membrane–particle interactions in an asymmetric flow field flow fractionation channel studied with titanium dioxide nanoparticles

    J. Chromatogr. A.

    (2014)
  • Working for a Caring Future Activity Report 2014, Cosmetics Europe,...
  • R. Corson et al.

    Stage Makeup

    (2015)
  • M.E. Burnett et al.

    Current sunscreen controversies: a critical review: sunscreen controversies

    Photodermatol. Photoimmunol. Photomed.

    (2011)
  • A. Gelabert et al.

    Uncoated and coated ZnO nanoparticle life cycle in synthetic seawater: ZnO nanoparticle life cycle in synthetic seawater

    Environ. Toxicol. Chem.

    (2014)
  • C. Contado

    Nanomaterials in consumer products: a challenging analytical problem

    Front. Chem.

    (2015)
  • H. Shi et al.

    Titanium dioxide nanoparticles: a review of current toxicological data

    Part. Fibre Toxicol.

    (2013)
  • A.P. Gondikas et al.

    Release of TiO 2 nanoparticles from sunscreens into surface waters: a one-year survey at the Old Danube Recreational Lake

    Environ. Sci. Technol.

    (2014)
  • V.L. Colvin

    The potential environmental impact of engineered nanomaterials

    Nat. Biotechnol.

    (2003)
  • C. Contado et al.

    TiO 2 in commercial sunscreen lotion: flow field-flow fractionation and ICP-AES together for size analysis

    Anal. Chem.

    (2008)
  • Regulation (EC) No 1223/2009 of the European Parliament and of the council of 30 November 2009 on cosmetic products,...
  • M. Okamoto et al.

    Fast analysis of trace amounts of lead in cosmetics by atomic absorption spectrophotometry cosmeticbsy atomic absorption spectrophotometry

    Soc. Cosmet. Chem.

    (1971)
  • Cited by (93)

    View all citing articles on Scopus
    View full text