Anti-aging cosmetics are often sought after in order to slow down the aging process. Free radicals are one of the main causes of skin aging, and therefore antioxidants are used in anti-aging cosmetics. The aim of this study was to investigate which method is the most suitable for determining the antioxidant capacity of these products. Having samples extracted, the antioxidant capacity of the extracts obtained was determined by the following spectrophotometric methods: DPPH, Folin-Ciocalteu, FRAP, the ABTS method and the ferroion chelation method with ferrosine. The antioxidant capacity of the samples varied depending on the extract type and the method used. DPPH and ferroion chelation measurements with ferrosine were carried out in the part of the spectrum where plant pigments absorb. These pigments are often found in anti-aging products affecting these methods measurement results. The Folin-Ciocalteu method is suitable for researching the antioxidant capacity of hydrophilic extracts, but not lipophilic ones, where turbidity and the formation of a gelled ring occur. The FRAP method revealed similar results for all the samples and proved to be less sensitive than the others. The ABTS method for both types of extracts has proven to be the most suitable and sensitive method for determining the antioxidant capacity of anti-aging products.

In this study, the preservation of As(III) in model solutions and natural groundwater samples from four locations in Croatia was conducted. Model laboratory samples were spiked with As(III) and As(V), and different complexing agents. Solutions were analysed in intervals of 24, 48 h and during ten days after preparation. Model samples containing citric acid, sodium citrate, sodium oxalate and potassium sodium tartrate in combination with acetic acid, spiked with As(III)and As(V), showed good species preservation. As(III), in model samples, was preserved for 7 days with citric acid, and citric acid in combination with acetic acid, as well as with tartrate. As(III), in natural samples, was preserved for 6 to 12 days with potassium sodium tartrate, citric acid, and citric acid in combination with acetic acid and showed improvement, compared with unpreserved samples (oxidation in 3 days). The results showed that acetic acid alone was not successful in preserving As speciation. Good resolution of inorganic arsenic species was achieved using differential pulse anodic stripping voltammetry technique (DPASV). Since this technique is comparatively cheaper and more convenient to use than other available techniques it could become a method of choice for arsenic speciation in water.

This study aimed to develop a rapid method for the separation of stigmasterol, campesterol and β-sitosterol in Prunus spinosa L. (blackthorn) fruit extracts by HPLC system. Samples were prepared by Soxhlet extraction method and separated on a C18 column using acetonitrile-methanol mobile phase and photodiode array detector (PDA). The optimized method resulted in a linear calibration curve ranging from 1.70–130 μg mL–1 for all three phytosterols. Analyses of external phytosterol standards showed good linearity (R2 of 0.998 to 0.999); LOD and LOQ were determined to be 0.32–9.30 μg mL–1 and 0.98–28.1 μg mL–1, respectively. Repeatability and reproducibility precision analyses showed acceptable values of %RSD. β-sitosterol was the predominant phytosterol (51.53–81.03% of total) among all samples. Method validation parameters indicated that this analytical method can be applied for accurate and precise determination of campesterol, stigmasterol and β-sitosterol, in selected extracts.