Commercial Sunscreen Formulations Research Articles

A comparative study of the in vitro dermal absorption of radiolabeled benzophenone through human skin

Octocrylene is a common sun filter ingredient used to protect the skin from damaging UV rays. Benzophenone is an impurity found in formulations containing octocrylene. [14C]-Benzophenone was spiked (0.1 g/L) into 2 commercial sunscreen formulations; Neutrogena® Beach Defense Sunscreen Spray Broad Spectrum SPF 70 Aerosol, Neutrogena® Ultra Sheer Body Mist Sunscreen Broad Spectrum SPF 30 Aerosol, and an acetone vehicle. The formulations were applied (ca 2 μL/cm2) to dermatomed human skin mounted in static diffusion cells in vitro. Receptor fluid was collected up to 24 h post dose. All samples were analyzed by liquid scintillation counting. The dermal delivery of [14C]-Benzophenone was 10.02, 9.04 and 5.19% for the 3 formulations. However, the [14C]-Benzophenone mass balances were low; 81.5, 85.3 and 8.02%, respectively. A volatility test was performed replacing skin with aluminum foil for the sunscreen formulations only. The [14C]-Benzophenone mass balance at dosing was 99% but fell to 56.9 and 60.6% at 24 h post dose, confirming the losses were due to [14C]-Benzophenone volatility. A conservative dermal absorption value of 12.42% was proposed to cover [14C]-Benzophenone containing formulations.

Boosting the effectiveness of UV filters and sunscreen formulations using photostable, non-toxic inorganic platelets.

We have studied the size-dependent optical scattering of aqueous suspensions containing Mg2Al-LDH platelets, which exhibit high total- and side-scatterings. By incorporating 3 wt% Mg2Al-LDH platelets (280 nm) in a commercial sunscreen formulation, we achieved a twofold Sun Protection Factor boost, providing a promising, high-efficient and non-toxic strategy to enhance sunscreen effectiveness.

Fish gut and skin microbiota dysbiosis induced by exposure to commercial sunscreen formulations

UV filters (organic or mineral) present in sunscreen products are emerging contaminants of coastal aquatic environments. There is an urgent need to understand marine organisms responses to these compounds. In this study, we investigated the effect of exposure to dilutions of commercial sunscreen formulations on bacterial communities of mullet (Chelon sp.). The gut and skin mucus microbial communities were characterized using a metabarcoding approach targeting the 16S rRNA gene. Our results revealed that mullets had its own bacterial communities that differ from their surrounding habitats and specific to tissue. The dilutions of commercial sunscreens modified the relative abundance of Actinobacteroita, Bacteriodota and Proteobacteria for both gut and skin microbiota. They also allowed to bacteria affiliated to Mycobacterium, Nocardia and Tenacibaculum genera, known to house pathogenic species, to colonize the epithelium which may have implications for fish host health.

Photostability Study of Avobenzone in Commercial Sunscreen SPF 45 with Additional SolaStay® Quencher Upon Sun Exposure

Avobenzone combined with various concentrations of Ethylhexyl Methoxycrylene (SolaStay® S1 quenchers) aims to see photostability studies. So that in this study tested the effect of SolaStay® S1 quenchers, SolaStay® quencher concentration, and the effect of irradiation time with sunlight on the photostability of avobenzone in commercial sunscreen formulations SPF 45. As well as determining the best SPF 45 commercial sunscreen formulations with the addition of Quenchers. The method used in this study is the spectroscopic method which uses two UV-VIS and HPLC spectrophotometer analyser. Based on the research data obtained in the presence of a quencher showed good photostability to avobenzone at certain quencher concentrations. Compared to F0, the effect of the addition of the quencher was very good, as seen from the relatively low decrease in the photodegradation rate compared to without the addition of the quencher. Viewed from the overall results, FSOL1 with the addition of 3% SolaStay® is the best SPF 45 sunscreen formulation of all formulations. This is seen from the small photodegradation results every time and the effect of skin effects was low. Keywords: Avobenzone, Quencher, Photostability, Photodegradation, SolaStay®, Sunscreen

Separating and Purifying Mycosporine-like Amino Acids from Cyanobacteria for Application in Commercial Sunscreen Formulations.

Using algal-derived mycosporine-like amino acids (MAAs) in sunscreen formulations is constrained by low cellular concentrations of MAAs and by the high costs associated with harvesting algal cells and extracting the MAAs. Here, we report an industrial scalable method using a membrane filtration approach to purify and concentrate aqueous extracts of MAAs. The method includes an additional biorefinery step enabling purification of phycocyanin, an established valuable natural product. Cultivated cells of the cyanobacterium Chlorogloeopsis fritschii (PCC 6912) were concentrated and homogenised to produce a feed for sequential processing through three membranes of decreasing pore size to obtain a retentate and permeate for each step. Microfiltration (0.2 µm) was used to remove cell debris. Ultrafiltration (10,000 Da) was used to remove large molecules and recover phycocyanin. Finally, nanofiltration (300-400 Da) was used to remove water and other small molecules. Permeate and retentate were analysed using UV-visible spectrophotometry and HPLC. The initial homogenised feed had a shinorine concentration of 5.6 ± 07 mg L-1. The final nanofiltered retentate resulted in a 3.3 times-purified concentrate (shinorine concentration of 18.71 ± 0.29 mg L-1). Significant process losses (35%) highlight scope for improvement. Results confirm the potential of membrane filtration to purify and concentrate aqueous solutions of MAAs with simultaneous separation of phycocyanin highlighting a biorefinery approach.

Separating and Purifying Mycosporine-Like Amino Acids from Cyanobacteria for Application in Commercial Sunscreen Formulations

Separating and Purifying Mycosporine-Like Amino Acids from Cyanobacteria for Application in Commercial Sunscreen Formulations

Intermolecular Interactions and In Vitro Performance of Methyl Anthranilate in Commercial Sunscreen Formulations

In order to afford the required level of broad-spectrum photoprotection against UV-B and UV-A radiation, sunscreens must contain a combination of UV filters. It is important that any interactions between UV filters do not adversely affect their photostability nor the overall photostability of the sunscreen formulation. In this work, we explore the feasibility of using methyl anthranilate (MA) as an alternative to the photo-unstable UV-A filter, avobenzone. From the in vitro studies presented here, we conclude that MA does not provide sufficient UV-A protection on its own but that it is more photostable in formulation than avobenzone. In addition, we found that both octocrylene (OCR) and ethylhexyl methoxycinnamate (EHMC), two commonly used UV-B filters, can stabilize MA through quenching of its triplet states, as previously reported, which has a demonstrable effect in formulation. In contrast with previously reported observations for mixtures of EHMC and avobenzone, we found no evidence of [2+2] photocycloadditions taking place between EHMC and MA. This work demonstrates how a clear insight into the photophysics and photochemistry of UV filters, as well as the interactions between them, can inform formulation design to predict sunscreen performance.

Attenuation of UV absorption by poly(lactic acid)-iron oxide nanocomposite particles and their potential application in sunscreens

The topical application of sunscreen and cosmetic products that afford protection from terrestrial ultraviolet radiation to reduce the risk of developing skin cancer is an integral part of modern sun protection. The current sunscreen formulations use inorganic zinc oxide (ZnO) and titanium dioxide (TiO2), that are highly photocatalytic, with the ability to penetrate the skin, and exhibit potential toxicity. In this study, we demonstrate a novel methodology to increase the sun protection factor (SPF) of encapsulated metal oxide (Fe2O3) nanoparticles in poly(lactic acid) (PLA) microspheres as ultraviolet filters for sunscreen applications. The combination of these two materials results in a nanocomposite with increased UV attenuation and without significant cytotoxic effects during in vitro evaluation. A commercial sunscreen formulation was used to show the benefits of the developed nanocomposites by replacing the harmful ZnO particles by the Fe2O3-PLA ones, and a throughout comparison between commercial and the new sunscreen formulation was performed. By adding a small amount of the novel Fe2O3-PLA particles, a remarkable increase in the SPF performance, from 40 (commercial ZnO formulation) to 50 was achieved just by replacing the ZnO particles with 5 wt% of Fe2O3-PLA ones, resulting in a high level of UV protection, coupled with lower dangerous photocatalytic activity when compared with commercial ZnO nanoparticles. The encapsulation of metal oxide nanoparticles by PLA could provide a route to improve the sunscreen efficacy and enhance its SPF by using more environmentally friendly materials.

Penetration of Zinc into Human Skin after Topical Application of Nano Zinc Oxide Used in Commercial Sunscreen Formulations.

Zinc oxide nanoparticles (ZnO NPs) are a key constituent of many commercial broad-spectrum sunscreens. Studies have shown that these NPs are retained on the superficial layers of the skins' barrier layer, the stratum corneum, and solubilized zinc species from the ZnO NPs have been shown qualitatively to penetrate intact human skin. The cytotoxicity of zinc is concentration- and species-dependent; however, to date, the amount of zinc permeating the skin strata is yet to be determined. Here, we applied commercial ZnO NPs to intact and impaired ex vivo barrier human skin. Artificial human sweat (to provide an electrolyte solution) and caprylic capric triglyceride (CCT; a common sunscreen formulation base) suspensions were applied to encompass potential "in-use" scenarios. A state-of-the-art multimodal approach analyzed zinc permeation. Our data show that elevated zinc concentrations within the skin are dependent on a number of variables, with barrier impairment and time being the most important factors followed by the vehicle, where sweat was more impactful than CCT. When ZnO NPs were applied to impaired barrier skin for 24 h, there was a 60-65-fold increase in zinc in the viable epidermis for both CCT and sweat compared to the control, increasing >100-fold after 48 h. Importantly, we identify that the localized cutaneous zinc concentration increase is not present as the nano ZnO that is used in sunscreens but only after dissolution and permeation as a different solubilized zinc species.

Systemic availability of lipophilic organic UV filters through dermal sunscreen exposure

BackgroundChemical UV filters are common components in sunscreens and cosmetic products and used to protect the skin against harmful effects of sunlight like sunburn. However, the effectiveness of sunscreens in the prevention of skin cancer is in some parts still controversial. Meanwhile, questions about negative effects of the chemical UV filters on human health arise and request an effective risk assessment. Real-life exposure data in humans after application of these products are still rare. Thus, we explored whether and to what extent UV filters are absorbed through the skin into the human body. Material and methodsPlasma and urine samples from 20 healthy volunteers were collected before, during and after a real-life exposure scenario (1st application: 2 mg/cm2; 2nd and 3rd (after 2 and 4 h): 1 mg/cm2 each) using a commercial sunscreen formulation for one day. These samples were analyzed for their content of the currently prominent UV filters octocrylene and avobenzone as well as 2-cyano-3,3-diphenylacrylic acid (CDAA) as the main octocrylene metabolite by using different liquid chromatography electrospray-ionization tandem mass spectrometric procedures. ResultsFollowing dermal sunscreen exposure, avobenzone, octocrylene and CDAA reached concentrations up to 11 μg/L, 25 μg/L and 1352 μg/L in plasma. In urine detection rates of avobenzone and octocrylene were low while CDAA showed a high detection rate and reached up to 5207 μg/g creatinine. Kinetic models could be fitted for octocrylene and CDAA in plasma and CDAA in urine. Concentration peaks were reached between 10 and 16 h after first application and half-life periods were in the range of 1.5 to 2 days. The lipophilic UV filter octocrylene and its metabolite CDAA showed a much slower elimination than other more hydrophilic UV filters. Concordantly, the metabolite CDAA in particular showed a markedly increased renal excretion over the whole sampling period and indicated high internal exposure to OC. DiscussionReal-life sunscreen usage leads to considerable bioavailability of organic UV filters and their metabolites which is rarely seen for other environmental exposures. A combined monitoring of the parent compound and its metabolites is important to fully address internal exposure to the UV filter in humans. Considering the kinetic profiles a prolonged systemic release due to depot formation in skin and a potential accumulation through multi-day exposure is presumed. High in-vivo loads call for a critical toxicological assessment of the UV filters and their metabolites.

Photoprotection assessment of olive (Olea europaea L.) leaves extract standardized to oleuropein: In vitro and in silico approach for improved sunscreens

Olive leaves contain higher amount of polyphenols than olive oil and represent a waste product from olive harvest and pruning of olive trees. The most abundant compound in olive leaves is oleuropein. Benefits of the topical application of olive leaves extract were previously reported, but little information is available on its photoprotective potential and the result of the association of this extract with organic UV filters in topical sunscreen formulations. The olive leaves extract photoprotective potential is less explored for both oral and topical photoprotection in comparison with other plants extracts and polyphenols, such as Polypodium leucotomos extract and resveratrol. There are increasing efforts towards developing more efficient sunscreens and a photoprotection assessement along with a better understanding of the photochemistry of naturally occurring sunscreens could aid the design of new and improved commercial sunscreen formulations. This study was designed to investigate the photoprotective potential of olive leaves extract standardized for oleuropein performing a set of in vitro and in silico tools as an innovative approach, highlighting yeast assays, in vitro Sun Protection Factor (SPF) and molecular modelling studies of UV absorption. This study supports the use of olive leaves extract for photoprotection, as an effective photoprotective, anti-mutagenic and antioxidant active, also showing a synergistic effect in association with UV filters with an improvement on in vitro SPF of sunscreen formulations.

One pot environmental friendly synthesis of gold nanoparticles using Punica Granatum Juice: A novel antioxidant agent for future dermatological and cosmetic applications

HypothesisThe interesting properties of Gold Nanoparticles (AuNPs) make them attractive for different application fields such as cosmetology, medicine and clinical nanotechnologies. In this work a fast, easy and eco-friendly method for the AuNPs synthesis is proposed by using the Punica Granatum Juice (PGJ) with potential dermatological and cosmetic applications. The AuNPs antioxidant activity, due to the presence of phenols from the juice, and their use as booster for improving the Sun Protection Factor (SPF) in commercial sunscreen formulations, are thus expounded. ExperimentsBy using appropriate amounts of PGJ and HAuCl4, under mild work conditions, AuNPs with a mean size of 100 ± 40 nm are observed and carefully characterized. Solution pH, temperature, and volume were also changed for optimizing the AuNPs formation and features. The antioxidant activity was studied, by evaluating the AuNP ability of scavenging the radical 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH). This finding was confirmed performing special experiments focused on the reaction between AuNPs and H2O2, by using suitable probes, such as 4-thiothymidine (S4TdR) and Cytochrome-c (Cyt-c). The SPF value was also calculated. FindingsThe synthetized AuNPs showed a surface plasmon in visible range at 577 nm and resulted stable for long time in aqueous medium, also changing the pH values in the range 2–12. The studied antioxidant activity, confirmed also by performing special experiments with suitable probes, demonstrated the high performance of AuNPs. The AuNP photostability under sun irradiation is also shown. The calculated SPF values were in the range 3–18, related to AuNPs concentration in the range 1.80 × 10−12–1.00 × 10−11 M. The same AuNPs concentrations were used for cellular experiments. Indeed, since the AuNPs-PGJ mediated will be potentially introduced by dermal contact, dermal fibroblasts (Human Dermal Fibroblasts, HDF) and Human Microvascular Endothelial Cells (HMVEC) were used to evaluate the possible effects of these nanoparticles as a preliminary step. The results indicated that an AuNP concentrations in the range 1.80 × 10−12–3.60 × 10−12 M could be adopted since they do not appeared cyctotoxic.

Commercial sunscreen formulations: UVB irradiation stability and effect on UVB irradiation-induced skin oxidative stress and inflammation

Evidence shows that sunscreens undergo degradation processes induced by UV irradiation forming free radicals, which reduces skin protection. In this regard, the biological effects of three commercial sunscreen formulations upon UVB irradiation in the skin were investigated. The three formulations had in common the presence of benzophenone-3 added with octyl methoxycinnamate or octyl salycilate or both, which are regular UV filters in sunscreens. The results show that formulations F1 and F2 presented partial degradation upon UVB irradiation. Formulations F1 and F2 presented higher skin penetration profiles than F3. None of the formulations avoided UVB irradiation-induced GSH depletion, but inhibited reduction of SOD activity, suggesting the tested formulations did not present as a major mechanism inhibiting all UVB irradiation-triggered oxidative stress pathways. The formulations avoided the increase of myeloperoxidase activity and cytokine production (IL-1β and TNF-α), but with different levels of protection in relation to the IL-1β release. Concluding, UVB irradiation can reduce the stability of sunscreens, which in turn, present the undesirable properties of reaching viable skin. Additionally, the same SPF does not mean that different sunscreens will present the same biological effects as SPF is solely based on a skin erythema response. This found opens up perspectives to consider additional studies to reach highly safe sunscreens.

Relative Penetration of Zinc Oxide and Zinc Ions into Human Skin after Application of Different Zinc Oxide Formulations.

Zinc oxide (ZnO) is frequently used in commercial sunscreen formulations to deliver their broad range of UV protection properties. Concern has been raised about the extent to which these ZnO particles (both micronized and nanoparticulate) penetrate the skin and their resultant toxicity. This work has explored the human epidermal skin penetration of zinc oxide and its labile zinc ion dissolution product that may potentially be formed after application of ZnO nanoparticles to human epidermis. Three ZnO nanoparticle formulations were used: a suspension in the oil, capric caprylic triglycerides (CCT), the base formulation commonly used in commercially available sunscreen products; an aqueous ZnO suspension at pH 6, similar to the natural skin surface pH; and an aqueous ZnO suspension at pH 9, a pH at which ZnO is stable and there is minimal pH-induced impairment of epidermal integrity. In each case, the ZnO in the formulations did not penetrate into the intact viable epidermis for any of the formulations but was associated with an enhanced increase in zinc ion fluorescence signal in both the stratum corneum and the viable epidermis. The highest labile zinc fluorescence was found for the ZnO suspension at pH 6. It is concluded that, while topically applied ZnO does not penetrate into the viable epidermis, these applications are associated with hydrolysis of ZnO on the skin surface, leading to an increase in zinc ion levels in the stratum corneum, thence in the viable epidermis and subsequently in the systemic circulation and the urine.

A sunblock based on bioadhesive nanoparticles.

The majority of commercial sunblock preparations utilize organic or inorganic ultraviolet (UV) filters. Despite protecting against cutaneous phototoxicity, direct cellular exposure to UV filters has raised a variety of health concerns. Here, we show that the encapsulation of padimate O (PO) - a model UV filter - in bioadhesive nanoparticles (BNPs) prevents epidermal cellular exposure to UV filters while enhancing UV protection. BNPs are readily suspended in water, facilitate adherence to the stratum corneum without subsequent intra-epidermal or follicular penetration, and their interaction with skin is water-resistant yet the particles can be removed via active towel drying. Although the sunblock based on BNPs contained less than 5 wt% of the UV-filter concentration found in commercial standards, the anti-UV effect was comparable when tested in two murine models. Moreover, the BNP-based sunblock significantly reduced double-stranded DNA breaks when compared to a commercial sunscreen formulation.

Stratum Corneum Is an Effective Barrier to TiO2 and ZnO Nanoparticle Percutaneous Absorption

Background: There is increasing concern over the local and systemic side effects of TiO₂ and ZnO coated nanoparticles widely used in sun blockers. Objective: To determine the localization and possible skin penetration of TiO₂ and ZnO nanoparticles, dispersed in 3 sunscreen formulations, under realistic in vivo conditions in normal and altered skin. Methods: Nuclear microscopy techniques provided spatially resolved quantitative analysis of Ti and Zn nanoparticle distributions in transversal cryosections of skin obtained by biopsy with no further treatment. A test hydrophobic formulation containing coated 20-nm TiO₂ nanoparticles and 2 commercial sunscreen formulations containing TiO₂ alone or in combination with ZnO were tried, taking into account realistic use conditions by consumers and compared with the recommended standard condition for the sun protection factor test. The protocols consisted of an open test. Results: Following a 2-hour exposure period of normal human skin to TiO₂- and ZnO-containing sunscreens, detectable amounts of these physical blockers were only present at the skin surface and in the uppermost stratum corneum regions. Layers deeper than the stratum corneum were devoid of TiO₂ or exogenous ZnO, even after 48 h of exposure to the sunscreen, under occlusion. Deposition of TiO₂ and ZnO nanoparticles in the openings of the pilosebaceous follicles was also observed, suggesting a preferential fixation area. Penetration of nanoparticles into viable skin tissue could not be detected. Conclusions: TiO₂ or ZnO nanoparticles are absent or their levels are too low to be tested under the stratum corneum in human viable epidermal layers. Therefore, significant penetration towards the underlying keratinocytes is unlikely.

Simultaneous quantitative estimation of oxybenzone and 2-ethylhexyl-4-methoxycinnamate in sunscreen formulations by second order derivative spectrophotometry

Simultaneous determination of 2-ethylhexyl-4-methoxycinnamate (OMC) and oxybenzone (OB) in commercial sunscreen formulations has been achieved by using second order derivative spectrophotometry. The analytical methodology described does not require elaborate pretreatment of samples. The results obtained could be validated by reverse phase HPLC assay by using isocratic methanol: water (88: 12) solvent system. The sensitivity of the developed derivative spectrophotometry method was determined to be 9.0 × 10−3 L/mg for OB and 9.56 × 10−3 L/mg for OMC. The limit of instrumental detection (LOD) was determined to be 0.6 mg/L for OB and 1.38 mg/L for OMC with relative standard deviation of 0.001 and 0.004 for OB and OMC respectively. The method developed can be used for quick assay of commercial sunscreens.

Kinetics of 3-(4-methylbenzylidene)camphor in rats and humans after dermal application

The toxicokinetics of 4-MBC after dermal administration were investigated in human subjects and in rats. Humans (3 male and 3 female subjects) were exposed to 4-MBC by topical application of a commercial sunscreen formulation containing 4% 4-MBC (w/w), covering 90% of the body surface and resulting in a mean dermal 4-MBC dose of 22 mg/kg bw. In rats, dermal 4-MBC doses of 400 and 2000 mg/kg bw were applied in a formulation using an occlusive patch for 24 h. Concentrations of 4-MBC and its metabolites were monitored over 96 h in plasma (rats and humans) and urine (humans). In human subjects, plasma levels of 4-MBC peaked at 200 pmol/ml in males and 100 pmol/ml in females 6 h after application and then decreased to reach the limit of detection after 24 h (females), respectively, 36 h (males). After dermal application of 4-MBC, peak plasma concentrations of 3-(4-carboxybenzylidene)-6-hydroxycamphor were 50-80 pmol/ml at 12 h and of 3-(4-carboxybenzylidene)camphor were 100-200 pmol/ml at 24 h. In male and female rats, peak plasma levels of 4-MBC were 200 (dose of 400 mg/kg bw) and 1 200 pmol/ml (dose of 2000 mg/kg bw). These levels remained constant for up to 24-48 h after dermal application. Peak plasma concentrations of 3-(4-carboxybenzylidene)-6-hydroxycamphor were 18,000 pmol/ml (males) and of 3-(4-carboxybenzylidene)camphor were 55,000 pmol/ml (females) between 48 and 72 h after application of the high dose of 4-MBC. In human subjects, only a small percentage of the dermally applied dose of 4-MBC was recovered in the form of metabolites in urine, partly as glucuronides. The obtained results suggest a more intensive biotransformation of 4-MBC in rats as compared to humans after dermal application and a poor absorption of 4-MBC through human skin.

Sequential injection analysis for benzophenone-4 and phenylbenzimidazole sulphonic acid in sunscreen sprays by solid-phase extraction coupled with ultraviolet spectrometry

A sequential injection UV method was developed to determine benzophenone-4 (BZ4) and phenylbenzimidazole sulphonic acid (PBS) simultaneously, these being the most commonly used UV-filters in aqueous formulations used as sunscreen sprays. The selective elution of both was performed by on-line solid-phase extraction, by retention on a SAX microcolumn and separation by varying the pH of elution. The sensitivity obtained was 0.042±0.001 ml μg −1 for PBS and 0.0159±0.0003 ml μg −1 for BZ4. The limit of detection was 1.6 μg ml −1 for PBS and 0.6 μg ml −1 for BZ4. The R.S.D. of the results was 1–6% for PBS and 1–12% for BZ4. The method was validated using commercial sunscreen formulations with concentrations determined by a liquid chromatographic procedure. The two procedures gave comparable results. Automation of the method means the amount of reagents used and residues generated are decreased. The system allows the required analysis sequence to be programmed using suitable software.

Simultaneous determination of oxybenzone and 2-ethylhexyl 4-methoxycinnamate in sunscreen formulations by flow injection-isodifferential derivative ultraviolet spectrometry

A flow injection procedure was developed for the simultaneous determination of two UV filters (oxybenzone and 2-ethylhexyl 4-methoxycinnamate) in sunscreen formulations, based on the isodifferential approach. The use of the second derivative spectra allowed a selective determination of the analytes free from matrix interferences and without pretreatment of samples. Standard solutions of the analytes were analyzed by the proposed procedure in order to select the appropriate wavelengths to solve the mixture. After this, the procedure was validated using commercial sunscreen formulations the concentrations of which were determined by an HPLC procedure. The two procedures gave comparable results. The sensitivity for oxybenzone determination by the proposed method was (9.2±0.1)×10 −5 ml μg −1, and the limit of instrumental detection was 0.5 μg ml −1. Determination of 2-ethylhexyl 4-methoxycinnamate had a sensitivity of (4.6±0.1)×10 −5 ml μg −1 and a limit of detection of 2.1 μg ml −1. The proposed flow injection procedure allowed on-line dilution of samples, and a sampling frequency of 360 h −1. The accuracy, speed and selectivity of the procedure make it suitable for this type of formulations.