Development and Validation of Method for the Quantitative Determination of Zinc in its Chelate Complexes Using Energy Dispersive X-ray Fluorescence Spectroscopy

Introduction. The production, standardization and quality control process of various dietary supplements containing chelated zinc requires validated quantitative assessment methods. In this work, we propose an X-ray fluorescence spectroscopy (XRF) technique for determining the zinc content in the composition of coordination compounds using the example of a synthesized chelate complex with methionine.Aim. To synthesize Zn(Met)2 chelate complex, to develop and validate a method for its quantitative analysis using the XRF method.Materials and methods. The synthesized zinc chelate complex was investigated by IR spectroscopy. The XRF method was used to develop a method for quantifying the zinc content in the synthesized complex. We used dry mixtures of zinc sulfate monohydrate and L-methionine (Met) in a molar ratio of Zn to Met – 1 : 1, 1 : 2, 1 : 4, 1 : 8 and 1 : 16 and also aqueous solutions of zinc sulfate and L-methionine in a molar ratio of Zn to Met 1 : 2 with Zn concentrations from 0.5 to 100 mmol/l as calibration standards. Complexometric titration was used as an arbitration method for the quantitative determination of zinc content in the samples under study.Results and discussion. The IR spectrum of chelate complex confirmed the presence of a donor-acceptor bond between Zn2+ and the nitrogen atom of amino group in methionine. The titration results showed chelate compounds have a composition corresponding to the stoichiometric formula Zn(Met)2. XRF analysis of dry standard mixed samples demonstrated the presence of matrix effect, that makes impossible an accurate assessment of zinc content in the chelate compound. According to the XRF spectra of aqueous solutions containing zinc sulfate and methionine in a ratio of 1 : 2 at a zinc concentration of 0.5; 1; 2; 3; 4; 5; 10; 25; 50 and 100 mmol/L, a calibration graph was constructed – the dependence of the fluorescence signal intensity for the Kα line of zinc on the concentration of zinc in the solution (r = 0.9996). The method was evaluated by the following validation parameters: specificity, linearity, correctness, precision, and analytical range. The specificity of the validated method was proven in the presence of copper, iron, and silver.Conclusion. The developed method make it possible to determine with sufficient precision and correctness the content of Zn2+ in its aqueous solutions of inorganic and organic nature by the XRF method in the concentration range from 3 to 100 mmol/l without the influence of the matrix.

A bis-chelate o-vanillin-2-ethanolamine copper(II) complex bearing both imine and amine forms of the ligand

The molecular bis-chelate complex (2-{[(2-hydroxyethyl-κO)amino-κN]methyl}-6-methoxyphenolato-κO)(2-{[(2-hydroxyethyl)imino-κN]methyl}-6-methoxyphenolato-κO)copper(II), [Cu(C10H14NO3)(C10H12NO3)] or [Cu(HL im)(HL am); HL im = C10H14NO3; HL am = C10H12NO3, represents the first compound containing a salicylidene-2-ethanolamine type ligand in both imino HL im (Schiff base) and amino HL am (reduced Schiff base) forms that has been structurally characterized on the basis of X-ray data. Two molecules of the monodeprotonated ligands coordinate the CuII ion in an (N,O phen)-bidentate and an (N,O phen,O alc)-tridentate fashion in the case of the imino and amino forms, respectively. The shape of the CuN2O3 coordination polyhedron is a distorted square-pyramid (geometry index τ5 = 0.26). Intermolecular N—H...O and O—H...O hydrogen bonds, involving H atoms of the amino and hydroxyethyl groups, create a two-dimensional supramolecular array extending parallel to (010).

Optimal 18F-fluorination conditions for the high radiochemical yield of [18F]AlF-NOTA-NHS complexes

18F-fluorination using aluminum-fluoride ([18F]AlF) chelate technique has been reported to give a low-to-moderate radiochemical yield, between 5 and 20%. Therefore, the work described here outlines the optimum 18F-fluorination condition for the formation of [18F]AlF2+ and [18F]AlF-NOTA-NHS complex with the radiochemical yield (RCY) and purity (RCP) of more than 90% as a prerequisite step before proceeding with the radiopharmaceutical preparation using the [18F]AlF-bifunctional chelator technique. As well as being simple, the suggested method is practical and relevant for beginners interested in 18F-fluorination with [18F]AlF-chelate complex technique or also for a researcher who aims to proceed on an extensive scale.

THE INVESTIGATION OF THE PENETRATION OF MICROELEMENTS OF A DIETARY SUPPLEMENT IN CRUCIAN MEAT BY VARIOUS METHODS OF SALTING

The expediency of improving the technological methods of processing unprofitable small fish and expanding the range of food products from them is substantiated. It is proposed to enrich the meat of freshwater fish with trace elements by adding to salt or brine during the salting of raw materials dietary supplements based on chelate complexes. The kinetics of penetration of micronutrients of a dietary supplement based on a chelate complex into the muscle tissue of crucian carp was studied by electronic paramagnetic resonance. The ambassador was held in three ways. According to the first dry method of salting, the fish was mixed with sodium chloride NaCl with the addition of a dietary supplement based on a chelate complex in the amount of 20… 25% and 0.1% by weight of raw materials, respectively. According to the second brine method, the fish was salted in brine, which was a solution of sodium chloride NaCl in the amount of 2 kg of salt per 1 kg of raw material. The amount of dietary supplement based on the chelate complex was 0.1% by weight of raw materials. According to the third method, the ambassador was carried out in brine with the same concentrations of sodium chloride and dietary supplements, but previously the fish raw materials were treated with ultrasound. Salting of fish was carried out for 6 days. The distribution of Mn ions in the plane (i, j) is investigated. The kinetics of the penetration of a microelement into the volume of crucian muscle tissue was studied by the EPR method. The kinetics of Mn2 + ion distribution in the studied muscle tissue samples and the tomogram of these surfaces were determined. The values of the area under the EPR spectra are normalized to the values of the area under the maximum EPR signal. For the maximum EPR signal for dry pickling, the signal from the liquid in which the raw material was during salting, and during the brine - the signal from the brine sample was selected. It is noted that the kinetics of penetration of the trace element is determined by the area of contact of the raw material with diffusing substances and the method of intensification of the internal transfer of these substances within the raw material. It was found that for brine and brine with pre-sonication, the amount of trace element in the depth of the crucian muscle tissue differs within the error. This indicates the homogeneity of the distribution of the trace element of the dietary supplement based on the chelate complex by such methods of salting.