A reliable and environmentally-friendly liquid-chromatographic method for multi-class determination of fat-soluble UV filters in cosmetic products

An environmentally-friendly analytical method for the simultaneous determination of 15 fat-soluble ultraviolet (UV) filters currently authorized by the European Union regulation on cosmetic products has been developed. The determination was performed by liquid chromatography with UV spectrophotometric detection. Different parameters, such as type of column, oven temperature, mobile phase composition and flow rate were studied. The best chromatographic separation was obtained under the following conditions: C18 column set at 60 °C and gradient ethanol:water (containing 1% formic acid and 20 mM of 2-hydroxypropyl-β-cyclodextrin) as mobile phase pumped at 1 mL min⁻¹. 2-Hydroxypropyl-β-cyclodextrin was added as mobile phase modifier to achieve the complete resolution of some of the chromatographic peaks. The 15 target compounds were separated in less than 30 min. The method was satisfactorily validated by analyzing three laboratory-made cosmetic samples besides of eleven commercially available cosmetic products containing different combination of the target UV filters. Good accordance of the found levels compared with those of the laboratory-made samples and those of the commercial samples (when available) was achieved. Moreover, excellent recoveries (97–104%) and good intra-day and inter-day precision values at different concentration levels, besides limits of detection values below the μg mL⁻¹ level, were obtained. These good analytical features, as well as their environmentally-friendly characteristics, make the presented method suitable not only for routine analysis in cosmetics industries, but also as candidate reference method for sunscreen analysis.     

Qualitative detection of diuretics and acidic metabolites of other doping agents in human urine by high-performance liquid chromatography–tandem mass spectrometry: Comparison between liquid–liquid extraction and direct injection

Direct injection of urine has gained interest in the field of analytical toxicology, including doping control analysis. However, implementation of a direct urinalysis method for the LC–MS/MS detection of 34 diuretics and 9 other doping agents yielded several analytical problems, which were not observed using a traditional liquid–liquid extraction. Therefore a comparative study was made between liquid–liquid extraction and direct injection. Comparison of validation results showed that the liquid–liquid extraction at pH 7 allows to analyze samples without major drawbacks regarding matrix effects. Hence, good sensitivity was observed and detection limits ranged between 1 and 250 ng/mL for all compounds. In the direct injection approach shifted retention times were observed for several acidic and basic compounds due to unwanted matrix effects. This shift was reduced by a 25-fold dilution of the urine samples. Besides the improved retention time stability the diluted samples also exhibited lower ion suppression than the undiluted ones. After 25-fold dilution, detection limits ranged between 10 and 250 ng/mL for all compounds. Since these detection limits are at or below the minimum required performance level, imposed by the World Anti-Doping Agency, the method could be applied to routine anti-doping analysis. Samples, previously declared positive, were reanalysed using both the liquid–liquid extraction and direct injection. With both techniques all 26 samples were found to be positive, showing the applicability of direct injection for the analysis of diuretics.