Application of microextraction techniques for indirect spectrophotometric determination of fluorides in river waters.

The present study is dedicated to development of improved method for determination of trace amounts of fluorides in natural waters which is based on the interaction of fluorides with ion associate (IA) of Al(III), salicylic aldehyde acylhydrazones (benzhydrazone (SABH) and 4-picolinhydrazone (SAPH)) and polymethine dye Astra Phloxine FF (AP). Comparison of analytical forms [Al(SABH)2]⋅AP and [Al(SAPH)2]⋅AP showed that the analytical system Al(III)-SAPH-AP is more effective, namely, a higher level of preconcentration of the analytical form is ensured by and extraction equilibrium is achieved faster. Based on the study, we propose a new, fast, simple, reliable, sensitive, and accurate method of the indirect UV-Vis-spectrophotometric determination of fluorides grounded on the interaction of fluorides with IA of Al(III), SAPH and AP with the utilization of vortex-assisted liquid-liquid microextraction (VALLME). The method is based on the discoloration of the microextract of IA of Al(III), SAPH and AP (Al-SAPH-AP) in presence of fluoride ions due to the formation of fluoride complexes of aluminum with higher stability. The effect of various factors has been studied. The optimal conditions of the UV-Vis-spectrophotometric determination of fluorides were defined as: pH 7.0-10.0, 1.0⋅10-6 mol⋅L-1 Al(III); 4.0⋅10-5 mol⋅L-1 SAPH; 1.0⋅10-6 mol⋅L-1 AP; λ = 560 nm. VALLME have been carried out in 250 µL of CCl4 at 20:1 vol ratios of aqueous and organic phases, with vortexing at 3000 rpm for 15 s followed by centrifugation at 2000 rpm for 2 min. The determination of fluorides is feasible in the presence of various interferences. The calibration curve shows the linear dependence in the range of 0.3-114 µg⋅L-1 of the fluorides concentration (R2 = 0.993) with the limit of detection of 0.086 µg⋅L-1 and the limit of determination of 0.284 µg⋅L-1. The accuracy of the proposed protocol of fluorides determination was verified towards a reference method on the samples of natural rivers waters (RSD 2.6-3.1%, recovery 98.3-101.4%).

Biologically Active Substance Content in Edible Plants of Zakarpattia and Their Elemental Composition Model.

Consumption of edible plants satisfies a significant part of human body needs in macro- and micronutrients while biologically active substances contain strong antioxidant properties and reduce the risk of a number of diseases. Balanced nutrition and design of personalized diets and treatment rely on the data on the content of macro- and micronutrients and biologically active substances. We determined polyphenol and anthocyanin content in 22 species of local edible plants using modified spectrophotometric method with Folin-Ciocalteu reagent as well as chemical elements' content in a mixture of edible plants from 13 regions using standard procedures. We performed correlational analysis of the obtained data and analysis of the main components in OriginLab, developed regional models of chemical elements' content for a mixture of edible plants, and conducted cluster analysis using common tools in Python. The results of biologically active substances' study demonstrated that the highest content of polyphenolic compounds and anthocyanins was found in grape meal of Vitis vinifera L. The study of chemical elements' content demonstrated that edible plants from lowland areas are the best and revealed clear dependences of the elements on each other and geographical conditions. The analysis of the principal components confirmed this finding. Based on the obtained data, a number of regional models of chemical elements' content in a mixture of edible plants were built, tested, and evaluated. Obtained results are the basis for designing various diets, filling composite databases of the region's food, and creating the newest biologics-pharmabiotics.

Screening of the microelements composition of drinking well water of Transcarpathian region, Ukraine.

BACKGROUND: For Transcarpathian region, with a pronounced landscape diversity of territories and significant areas of nature reserves, well water is an important source of drinking water. Screening of the microelement composition of drinking well water in Transcarpathia has not been carried out before. The microelement composition of such well water can be considered as the natural (baseline) indicator of quality. METHODS: We screened of the microelement (Cu, Zn, Fe, P, Ca, Mg, Mn, Mo, Co, As, Se, I, Br and F) composition of drinking well water in Transcarpathian region (for all 13 districts). Standard methods were used to determination the concentration of chemical elements in well water: electrothermal atomic absorption spectroscopy (Cu, Zn, Fe, Mn, Mo, Co), flame photometry (Ca, Mg), inverse voltammetry (total iodine), potentiometry (F, Br), fluorimetric (Se) and spectrophotometric methods (P, As). RESULTS: The content of chemical elements in well water varies over a wide range, in particular for Cu: 3.27-11.6 µg⋅L-1, Zn: 8.16-38.2 µg⋅L-1; Fe: 37.9-411 µg⋅L-1; P: 51.4-193 µg⋅L-1; Ca: 85-139 mg⋅L-1, Mg: 10.2-18.9 mg⋅L-1, Mn: 22.8-78.1 µg⋅L-1; Mo: 2.33-8.96 µg⋅L-1; Co: 1.72-3.38 µg⋅L-1; As: 2.9-17.4 µg⋅L-1; Se: 0.95-3.6 µg⋅L-1; I: 0.94-4.4 µg⋅L-1; Br: 712-3098 µg⋅L-1; F: 71-149 µg⋅L-1. The tendency that the content of microelements (Cu, Zn, Mn, Mo, Co, As, Se, I, Br, and F) in well waters of different landscape zones was evaluated through Spearman's coefficients. The content of trace elements in the waters of different landscape zones increases in the series: lowland landscape > foothill landscape > mountainous landscape (Spearman's coefficients: Cu - 0.62, Zn - 0.85, Mn - 0.69, Mo - 0.83, Co - 0.79, P - 0.74, As - 0.72, Se - 0.75, I - 0.80, Br - 0.91, F - 0.73). CONCLUSION: It is shown that the chemical composition of well water can be considered as the natural (baseline) indicator of quality of groundwater in Transcarpathia, taking into account topographic and geochemical features of the territories. Among the main problems of drinking well water in Transcarpathia are the relatively high content of Fe (typical for different landscape zones), as well as the low content of Se, I and F. The correlation of inter-elements content of chemical elements in drinking well waters of Transcarpathia has been revealed. The most pronounced correlations are observed for such pairs of microelements: Co-Mo (r > 0.95), I-Br (r > 0.92), Zn-Br (r > 0.89), Cu-Co (r > 0.84), Se-Co (r > 0.84), Mo-P (r > 0.84), Mo-I (r > 0.82) and Zn-Mo (r > 0.80).