Determination of Titanium Dioxide in Commercial Sunscreens by Inductively Coupled Plasma-Optical Emission Spectrometry

ABSTRACT A variety of sunscreen products have been developed to afford the consumer protection against some of the deleterious effects, for example erythema, caused by solar ultraviolet radiation. The requirement that suncare products offer broad-spectrum protection has resulted in the use of inorganic oxides, such as micronized titanium dioxide (TiO 2 ), in their formulation. However, there are now concerns about the photocatalytic effects of the TiO 2 in these products and its potential phototoxicity to the skin through the generation of reactive oxygen species such as hydroxyl and superoxide anion radicals. It is important, therefore, that the amounts of TiO 2 in suncare products be closely monitored and maintained within stipulated ranges. A simple, fast and reliable analytical method for the determination of TiO 2 in commercial sunscreen products by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed and validated. The limits of detection and quantitation were found to be 0.018 and 0.062 µg mL -1 , respectively. The average percentage recovery of TiO 2 was 102.32 ± 2.87 % with a RSD of 2.81 %. The method was applied to determine the concentration of TiO 2 in 22 commercial suncare samples of which 14 contained TiO 2 . The amounts of TiO 2 measured in these sunscreens ranged from 0.05 to 3.21 %. To our knowledge this is the first study that reports the amounts of TiO 2 in sunscreen products available on the South African market. KEYWORDS Titanium dioxide, sunscreens, physical blocker, inductively coupled plasma-optical emission spectrometry

The effect of synthesis method on the structure, and magnetic and photocatalytic properties of hematite (α-Fe2O3) nanoparticles

Samples of hematite (α-Fe2O3) nanoparticles have been synthesized through the co-precipitation route in cetyltrimethylammoniumbromide (Hem_PR), via a citric acid sol-gel method (Hem_SG) and a modified sol-gel method inTween20 (Hem_TW), and each were annealed at three different temperatures (400, 500 and 600 °C). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission and high-resolution electron microscopy (TEM and HRTEM), Mössbauer spectroscopy and by means of a vibrating sample magnetometer (VSM). In addition, the photocatalytic behaviour of each sample was tested on the degradation of rhodamine B (RhB) in solution. All the characterization techniques showed the formation of phases of pure hematite nanoparticles with improved crystallinity after higher temperature annealing. However, the nanoparticles synthesized in Tween 20 showed the smallest particle size and highest BET surface area, saturation magnetization and photocatalytic activity. Of particular note was the ability of Tween 20 to control the growth of the particles so that grain sizes well below 10 nm were obtained. Thus, Tween 20, when used as a surfactant in the sol-gel route, can serve to improve the physical properties of synthesized hematite nanoparticles.Keywords: Hematite, nanoparticles, Mössbauer spectroscopy, magnetic properties, Tween 20, photocatalysi

Redetermination of chlorido(2,2′:6′,2′′-terpyridine-κ3 N,N′,N′′)gold(I) dichloride trihydrate at 173 K

The redetermined structure of the title compound, [AuCl(C15H11N3)]Cl2·3H2O, at 173 (2) K is reported. The structure displays O—H⋯Cl and O—H⋯O hydrogen bonding. The distance of one of the chloride ions from the gold(I) atom [5.047 (1) Å] differs from that determined previously

Polybrominated Diphenyl Ethers (PBDEs) as Emerging Environmental Pollutants: Advances in Sample Preparation and Detection Techniques

Environmental pollution has been a challenging phenomenon in most developing countries, due to the weak enforcement of environmental regulations. As a result, humans and animals are exposed to different environmental pollutants, which threaten their very existence. Some of the emerging pollutants of great concern are polybrominated diphenyl ethers (PBDEs) since they are categorized as probable human carcinogens and are also known to bioaccumulate in fatty tissues of animals and humans, reaching toxic levels upon continued exposure. Monitoring of these pollutants is therefore paramount as it contributes to addressing the problem of human exposure and environmental pollution. Their monitoring involves sample preparation methods followed by quantification with various detection techniques. Sample preparation methods that aim at reducing matrix interferences, enriching analytes and transfer of analytes to a desirable solvent, have evolved from conventional methods to advanced methods that facilitate the detection of these chemicals at very low concentrations. Likewise, detection techniques have advanced from chromatographic detection techniques to miniaturized systems that involve sensors. This chapter discusses PBDEs as emerging pollutants, their sources, and toxicological implications on humans, as well as advances in sample preparation methods and detection techniques in the determination of PBDEs

Self-organization with traveling waves: A case for a convective torus

A traveling wave of BaSO4 in the chlorite-thiourea reaction has shown concentric precipitation patterns upon being triggered by the autocatalyst HOCl. The precipitation patterns show circular rings of alternate null and full precipitation regions. This self-organization appears to be the result of the formation of a convective torus. The formation of the convective torus can be described as a Benard-Marangoni instability with lateral heating

Determination of Titanium Dioxide in Commercial Sunscreens by Inductively Coupled Plasma-Optical Emission Spectrometry

ABSTRACT A variety of sunscreen products have been developed to afford the consumer protection against some of the deleterious effects, for example erythema, caused by solar ultraviolet radiation. The requirement that suncare products offer broad-spectrum protection has resulted in the use of inorganic oxides, such as micronized titanium dioxide (TiO 2 ), in their formulation. However, there are now concerns about the photocatalytic effects of the TiO 2 in these products and its potential phototoxicity to the skin through the generation of reactive oxygen species such as hydroxyl and superoxide anion radicals. It is important, therefore, that the amounts of TiO 2 in suncare products be closely monitored and maintained within stipulated ranges. A simple, fast and reliable analytical method for the determination of TiO 2 in commercial sunscreen products by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed and validated. The limits of detection and quantitation were found to be 0.018 and 0.062 µg mL -1 , respectively. The average percentage recovery of TiO 2 was 102.32 ± 2.87 % with a RSD of 2.81 %. The method was applied to determine the concentration of TiO 2 in 22 commercial suncare samples of which 14 contained TiO 2 . The amounts of TiO 2 measured in these sunscreens ranged from 0.05 to 3.21 %. To our knowledge this is the first study that reports the amounts of TiO 2 in sunscreen products available on the South African market. KEYWORDS Titanium dioxide, sunscreens, physical blocker, inductively coupled plasma-optical emission spectrometry