Validation of a high performance liquid chromatography method for sunscreen determination in cosmetics

The aim of this research was the development and validation of a high performance liquid chromatography (HPLC) method for the simultaneous and quantitative determination of benzophenone-3, octyl methoxycinnamate and octyl salicylate contained in sunscreen emulsions. The separation and quantitative determination was achieved using a LiChrospher((R)) 100 RP-18 (5 microm) Merck column, a mobile phase constituted of methanol/water (85/15, v/v), a flow-rate of 1.0 mL min(-1) and UV detection at 310 nm. The correlation coefficients and percentage of recovery for benzophenone-3, octyl methoxycinnamate and octyl salicylate were 0.9999 and 99.46%; 0.9995 and 98.85%; 0.9998 and 98.84%, respectively. The relative standard deviations (RSD) for commercial samples were between 0.50 and 0.70%.     

Importance of sunscreen products spreading protocol and substrate roughness for in vitro sun protection factor assessment

The purpose of this study was to evaluate the impact of substrate roughness and of product spreading method on in vitro sun protection factor (SPF) measurement and to define the experimental conditions most appropriate to reach the best level of correlation to in vivo SPF. In vitro SPF assessment was carried out on 13 products (including different formulation types with SPF from 20 to 75) using various in vitro SPF protocols and comparing related predictive potential regarding in vivo SPF. In the first part, two spreading methods were compared on two types of PMMA (Polymethyl methacrylate plate with different roughness. The impact of a second spreading step after product drying was also evaluated. From the various investigated parameters, it was shown that (i) a higher roughness (Ra = 4, 5 μm) was preferred for O/W formulations (ii) using a defined sequence of light linear and circular strokes was more adequate than monitoring product spreading in terms of time and pressure (iii) both correlation to in vivo SPF and results variability were improved when a second spreading step was added. The altered protocol showed a good predictive potential regarding in vivo SPF values for O/W formulations (correlation coefficient 0.92, correlation curve slope 0.98) and coefficient of variation of in vitro results (14% of the mean SPF value) close to what is usually obtained in vivo . The repeatability of the protocol was also demonstrated. In the second part, we evaluated the impact of PMMA plate pre-treatment with paraffinum liquidum before spreading the product to get a better correlation between in vivo and in vitro SPF values for W/O formulations. This allowed us to define a protocol suitable for both O/W and W/O formulations.     

Transparent formulations of a liposoluble sunscreen agent in an aqueous medium

Transparent formulations of a liposoluble sunscreen in an aqueous medium were studied, taking into account the different chemicals of a selected system situated in the vertices of a regular tetrahedron: sunscreen agent, co-solvent, (surfactants ± mineral oil) mixture (in the tetrahedron base) and water as the fourth component. Several compositions were selected at optimized component ratios after which water was added progressively. Clear gel and liquid compositions were obtained yielding a sunscreen agent that it suitable for conventional use. The physico-chemical properties of some compositions were assessed in terms of water/sunscreen agent content.     

Evaluation of antimicrobial effectiveness of C-8 xylitol monoester as an alternative preservative for cosmetic products

Xylitol is a natural sugar derived from plants, fruits and vegetables, whose antimicrobial properties are described in the literature. This study aimed to evaluate the antimicrobial effectiveness of C-8 xylitol monoester, for its use as a preservative in cosmetic formulations. The minimum inhibitory concentration (MIC) was determined by the broth macrodilution method, and the antimicrobial effectiveness of C-8 xylitol monoester was determined by using challenge test method. The results obtained in the determination of minimum inhibitory concentration are between 1.0% and 1.25% for Staphylococcus aureus, Escherichia coli and Candida albicans and between 1.0% and 1.5% for Pseudomonas aeruginosa and Aspergillus niger. The amount of 1% of C-8 xylitol monoester was added to the lotion used in the challenge test, observing a rapid decline in the number of CFU g(-1) in stages of evaluation after contamination of the product by all bacteria. The same occurs in relation to C. albicans, which shows a 90% reduction in the number of CFU g(-1). Regarding A. niger, similar reduction is observed when pH value of the lotion is adjusted from 5.5 to 7.0. The results indicate that under the tests conditions, C-8 xylitol monoester has antimicrobial activity and could be considered as an alternative preservative for cosmetic formulations.     

Chemico-physical and functional properties of inorganic sunscreens in cosmetic products

This paper reports preliminary results of a study carried out on liquid crystal emulsions added to three different inorganic sunscreens: ultrafine zinc oxide, ultrafine titanium dioxide (inorganic-treated) and ultrafine titanium dioxide (organic-treated hydrophobically).
The aim of the work was to investigate the influence of chemico-physical properties of inorganic sunscreens on the microstructure of cosmetic emulsions. The study was carried out using three different techniques: rheological measurements performed in dynamic conditions, to study the homogeneity of samples and their structural features; dispersion of powders in emulsions by optical microscopy and SEM/EDX analysis; and functionality of emulsions by UV spectroscopy, with adhesive tape as substrate.
Results show that the different chemico-physical properties of the micropigments lead to different interactions with emulsion components; these interactions may affect the functionality and microstructure of the whole system, with loss of stability.     

Adequacy of cosmetic preservation: chemical analysis, microbial challenge and in-use testing

The adequacy of preservation of seven previously unopened commercial cosmetic products was tested by individual challenges with Aspergillus niger ATCC 9642, Candida albicans ATCC 10231, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 15422, and Staphylococcus aureus ATCC 6538, using the Cosmetic, Toiletry, and Fragrance Association (CTFA) method. Each product was consecutively challenged three times, 28 days apart. Inoculated composite products were counted by conventional techniques at eight prefixed intervals. Six of seven cosmetics passed the CTFA acceptance criteria. On the basis of viable counts seven days after inoculation (CTFA criteria), the products were classified as follows: five products were well preserved, one was marginally preserved, and one was poorly preserved. The poorly preserved product failed the CTFA criteria for all three bacteria tested. Concentrations of preservative ingredients in uninoculated composites were determined by high performance liquid chromatography. All preservatives listed on the labels of the seven cosmetic products were identified by chemical analysis. Tentative in-use validation of the CTFA criteria was performed for three of the seven cosmetic formulations. The results suggested that some cosmetic products may be underpreserved.     

Utilization of electrochemical silver ions as preservative agent in cosmetic dispersions

The use of anodic silver ions as preserving agents in cosmetics was tested by a challenge test in a set of cosmetic dispersions with the addition of known preservative inhibitors or micro-organism growth-promoters such as humectants, hydrosoluble collagen and vegetable extracts. Silver's microbicidal efficacy, compared to that of imidazolidinyl urea or methyl p-hydroxybenzoate, showed a more efficient activity especially in the presence of proteinaceous material. This agent may represent a good and safe protection for finished products both in manufacture and during use.  

Re´sume´

Nous avons ve´rifie´, avec des `challenge tests', l'hypothe`se de l'utilisation du pouvoir microbicide des ions argent e´lectrochimiques dans les produits cosme´tiques. Ces ions produisaient une excellent pre´servation me^me en pre´sence des additifs, comme les hydratantes, les de´rive´s prote´iques ou les extraites ve´ge´tales, capables d'une remarquable inhibition contre les pre´servatifs ou capables de soutenir la croissance des micro-organismes. Les re´sultats expe´rimentaux, obtenus en diffe´rentes dispersions cosme´tiques, indiquent que les ions argent e´lectrochimiques peuvent e^tre utilise´s avec succe`s pour re´aliser une protection sure et tre`s efficace.     

A novel ex vivo technique to assess the sand/rub resistance of sunscreen products

A novel ex vivo technique has been used to assess the sand/rub resistance of topical sunscreens. The technique is based on transmission spectrometry using excised human epidermis as the substrate. The sun protection factors (SPFs) of 10 sunscreen products were measured prior to, and after agitation with sand. It was found that the different products retained varying amounts of their photoprotection after agitation, ranging from 40 to 85%. This technique provides a less expensive, less time-consuming and less experimentally problematic alternative to in vivo testing.     

Preservative systems containing essential oils in cosmetic products

The aim of this study was to evaluate the antimicrobial activity of selected essential oils ( Laurus nobilis , Eucalyptus globulus and Salvia officinalis ), both alone and in combination, in cosmetic preparations characterized by an increasing risk of microbial contamination, i.e. an O/W skin cream, a hydrogel and a non-alcoholic hydrolyte. Their potential synergistic effect in combination with the usual cosmetic preservatives at low concentrations (up to 200-fold less than usual) was also investigated.     

Dispersions of lamellar phases of non-ionic lipids in cosmetic products

Although aqueous dispersions of lipids in the form of particles having a lamellar structure (liposomes) are already known as excellent vehicles for pharmaceutical substances, their usefulness in cosmetic formulations has not been demonstrated. The present work shows the advantages obtained by application of such systems to the skin, and in particular the use of non-ionic lipids in aqueous dispersions. Thus, in comparison with classical formulations such as emulsions, these systems exhibit lower toxicity and permit closer control of the availability of active substances at the stratum corneum. As examples, compositions suitable for skin moisturising and for tanning products are presented. Dispersions de phases lamellaires de lipides non-ioniques en cosmétique     

Capillary electrophoresis as analytical method for active ingredient determination in cosmetic matrices

Capillary electrophoresis (CE) has emerged as an important technique applied to analytical chemistry and quality control. In the cosmetic field ascorbic acid is important for soothing, bleaching and for its scavenger activity. Ascorbic acid is responsible for great number of physiological oxidations in electron transfer reactions. Many natural substances have a functional activity which is very difficult to preserve or even to prolong with the requested and expected treatment. This paper reports the study of capillary electrophoresis for the characterization of ascorbic acid as the active ingredient in a new delivery system that is able to preserve stability and to prolong release of ascorbic acid according to the concentration needs of a cosmetic formulation.     

Predicting the efficacy of sunscreens in vivo veritas

A novel in vitro technique for measuring the efficacy of sunscreens over the skin surface is described. It is demonstrated that those products that spread easily are associated with both a low variance in delivered SPF and a subjective assessment of a product that is pleasing to use, which in turn results in a higher application thicknesses and greater delivered photoprotection leading to improved health benefits of sunscreen use.     

Poly(D,L-lactide) nanoencapsulation to reduce photoinactivation of a sunscreen agent

The use of sunscreens is the 'gold standard' for protecting the skin from ultraviolet light. Octyl methoxycinnamate (OMC) is one of the most widely used UVB filter but it can act as a sensitizer or photoallergen. When exposed to sunlight, OMC can change from the primary trans-form to cis-form and the isomerization, not reversible, conducts to a reduction of the UVB filtering efficiency because the trans-form has a higher extinction coefficient. Photostability is the most important characteristic of effective sunscreens and it can be influenced by formulation ingredients and by applying technological strategies. In this work, photostability experiments, performed on emulsion-gels containing different percentages of OMC free or loaded in poly(D,L-lactide) nanoparticles, were carried out. The presence of a polymeric envelop may act to protect the active ingredient. In this study, the influence of poly(D,L-lactide) matrices on the photochemical stability of the sunscreen agent was investigated. As highlighted in this study, free OMC in different formulations has different photoisomerization degree. Moreover, a dissimilar behaviour was observed by studying different sunscreen concentrations in the same cosmetic formulation. Photostability results show a significant reduction in photoisomerization degree for formulations containing sunscreen loaded in nanoparticles, highlighting that the encapsulation is a suitable strategy to improve OMC photostability. Moreover, sun protection factor (SPF) results show that the UVB filter protective power is also maintained after encapsulation.     

Applications of ternary systems in specific cosmetic formulations

The study of ternary systems leads to the understanding of the physico-chemical aspect and allows the contribution of the different components to a cosmetic formulation to be developed.
The present investigation was centred in the zone of transparent get belonging to a previously studied ternary system containing a broad variety of different structural compositions. The possibility of including an active sunscreen as well as the ability to increase the water content of the gel was studied.
The microscopical study of the compositions with polarized light allowed us to assign the corresponding different structures. A correlation between these structures and their physico-chemical properties, with special emphasis to rheology, has been established.     

Glyceridic esters of p-methoxycinnamic acid. A new sunscreen of the cinnamate class

Synopsis
The aim of this work was to investigate whether a 1,3-diacylglycerol moiety can act as enhancer of the photoprotecting action of a new sunscreen of the cinnamate class, owing to its affinity with skin constituents and lower susceptibility to hydrolysis at C-2. The sun protection factors (SPF) for 1,2,3-propanetriol 1,3-dipalmitate-2- p -methoxycinnamate and 1,2,3-propanetriol 1,3-dioctanoate-2- p -methoxy-cinnamate (2.0, 4.5 and 7.5%) were determined. The sunscreen preparations presented SPF values between 4.7 and 16. The results show that although glyceridic esters present higher lipophilicity and are more stable towards enzymatic hydrolysis in vitro , the synthesized triacylglycerols and the standard sunscreen 2-ethylhexyl p -methoxycinnamoyl (EHPM) showed equivalent SPF values for both methods.
Résumé
L'objectif de ce travail a été l'évaluation du groupe 1,3-diacylglycérol en tant qu'un agent d'intensification de la propriété photoprotectrice d'un nouveau filtre solaire de la classe cinnamate, en considérant l'affinité de cet groupe avec les matériels constitutifs de la peau et leur stabilité vis-à-vis l'hydrolyse enzymatique sur la position C-2. Les facteurs de protection solaire (FPS) des produits 1,2,3-propanetriol 1,3-dipalmitate-2-ρ-methoxy-cinnamate et 1,2,3-propanetriol 1,3-dioctanoate-2-ρ-methoxy-cinnamate ont étéévalués (2.0, 4.5 et 7.5)., Selon la concentration des produits, les préparations ont les valeurs de FPS entre 4.7 et 16. Les produits synthétisés ont les FPS équivalents au filtre solaire utilisé comme référence ( ρ -methoxy-cinnamate 2-ethylhexyl). Néanmoins, ils ont une plus important lipophilie et une plus grande stabilité vis-à-vis l'hydrolyse enzymatique in vitro.     

花草美容茶饮料生产工艺研究

以5味中草药为原料,对花草美容茶饮料生产工艺进行研究.结果表明,花草茶的最佳原辅料配比为玫瑰花3%,桃花2%,茉莉3%,薄荷叶1%,甘草1%,蜂蜜6%,稳定剂(黄原胶:CMC=1:1)0.1%;该配方在100 ℃浸提30 min所得的产品黄酮含量较高.     

Comparison of sun protection factors determined by an in vivo and different in vitro methodologies: a study with 58 different commercially available sunscreen products

An extensive study on the sun protection factors (SPF) of sun care products was carried out using the COLIPA (The European Cosmetic Toiletry and Perfumery Association) method, which relates to in vivo experiments. Furthermore, in vitro methods were tested with sunscreen formulations that were prepared as films on surface-roughened plates of polymethyl methacrylate (PMMA). One of the in vitro methods, i.e. using the sunscreen tester, has been recently developed, whereas the second has been defined by a pure spectroscopic approach, which is based on spectral transmission measurements of sunscreen films. Altogether 58 different sunscreen formulations, with manufacturer declared SPF values ranging from 4 to 60 and currently available on the European market, were investigated. The quality of correlations with results from the individual products based on the different in vitro methods versus the COLIPA values that were considered as generally accepted standard values was assessed. In this context, also variations because of sample preparation and spectral measurement were discussed. For sunscreen products with in vivo SPF values larger 25, the spectral transmittance within the UVA/UVB range is rapidly decreasing, which is experienced even for products with reduced amounts reaching 0.5 mg cm(-2) and still leading to unsatisfactory correlation of the spectroscopically derived SPF values versus the results from the alternative assays. Opposite to these small amounts, a sunscreen product spread of 2 mg cm(-2) is standard for the in vivo COLIPA method, whereas an area-normalized amount of 1 mg cm(-2) is currently routinely used for the sunscreen tester method. Furthermore, an overview of the individual product characteristics, such as their specific critical wavelengths and their UVA/UVB ratios is provided; both parameters can also be calculated from the spectral absorbances of the standardized sunscreen films.     

离子液体萃取/HPLC测定水产品中司帕沙星残留研究

建立了以离子液体([HMIm]BF4)为萃取剂,HPLC检测水产品中残留司帕沙星的方法,采用反相SpherisorbC18色谱柱(250mm×4mmi.d.,5μm),流动相为甲醇,流速:0.5mL/min,检测波长:298nm。在0.06～0.18mg/mL浓度范围内,方法线性良好(R2=0.9988),回收率为88.7%～93.0%,日内和日间的RSD介于2.1%～3.7%。方法准确可靠,重现性好,灵敏度高,适用于水产品中残留药物的检测。     

Proposed protocol for determination of photostability Part I: cosmetic UV filters

The protocol described here has been developed to measure the stability of UV-B filters; a modified version is recommended for UV-A filters. It should be considered as a tool to predict the effectiveness remaining after exposure to UV-A and UV-B light. It is a simple and reliable in vitro model simulating conditions of actual use. The results show that each filter requires an appropriate choice and fine tuning of reproducible analytical conditions. While absolute values are directly influenced by uncertainties in irradiance (dosimetry), comparative measurements with respect to a known standard are very reliable.     

A rapid High Performance Liquid Chromatographic (HPLC) method for the simultaneous determination of seven UV filters found in sunscreen and cosmetics

A rapid High Performance Liquid Chromatographic (HPLC) method was developed for the simultaneous determination of seven Ultra Violet (UV) filters most commonly found in cosmetics and sunscreen. The object of the method development was to provide a reliable rapid method, that would simultaneously separate a combination of the UV Filters, most commonly found in cosmetics and sunscreen products, utilizing a minimum of environmentally friendly solvents. The compounds separated were: benzophenone 3 (BZ3), methylbenzildene camphor (MBC), octyl dimethyl PABA (ODP), octocrylene (OCR), octyl methoxycinnamate (OMC), butyl – methoxydibenzoylmethane (BDM) and octyl salicylate (OS). An adjusted mobile phase consisting of ethanol and 1% acetic acid, combined with a Thermo Hypersil C₁₈ BDS 3 micron column resulted in a method, which allowed the analysis of the seven compounds in seven minutes. The proposed method was validated utilising the International Congress on Harmonisation (ICH) and the Food and Drug Administration (FDA) guidelines. All parameters examined were found to be well within the stated guidelines.