Visual-test and Sorption-spectrophotometric Determination of Melamine in Biological Objects

Melamine may have toxic effects on humans and animals. It is well known that melamine accumulates in the body and causes reproductive damages, forms bladder or kidney stones, which can lead to bladder cancer. Trace amounts of melamine at ppm levels may occur in certain food commodities due to its migration from melamine-containing disposable tableware plastics. It was intentionally adulterated to milk products to show a false increase in protein concentration. Considering these facts there is a need for establishing sensitive and reliable methods of melamine determination. As uncostly, rapid and selective melamine detection methods are highly required, the hyphenated sorption-spectrophotometric and visual test methods seem to be perspective candidates.In the present work the optimal conditions of sorption concentration of melamine from aqueous solutions ontо the silica gel surface were studied. The calibration graph for the sorption-spectrophotometric method is linear in 0.02 – 9.8 μmol.L-1 mg L-1 melamine concentration range. Proposed method allows naked-eye monitoring of biological samples.

Physico-chemical properties of β-diketone phosphorus-containing dendrimers

Protolytic, absorbance and fluorescence properties of β-diketone phosphorus-containing dendrimers based on cyclotriphosphazene core were studied. Dendrimer solutions in acetone are characterized by intense absorbance band at ≈ 340 nm (ε340≈ 8.5·104L/mol·сm) and fluorescence band with maximum at 440 nm. Position of these maxima does not change in various solvents, unlike the bands of monomer β-diketone. It was found that dendrimer aggregation is accompanied by appearance of a second absorbance band ε400≈ 4.5·103L/mol·сm, by red shift of emission spectra ∆λ ≈ 10 nm and also by decrease in surface tension of acetone solution. Ability of dendrimer aggregates to solubilize organic substrates was observed with the fluorescent indicator acridine

A Conceptual Rationale for a Contemporary Unified Code of Ethics in Ukraine

The globalization of psychology-counseling in Ukraine began about 30 years ago. Since the establishment of applied psychology in the early 1990s, the pro- fession is still forming its standards of education, training, and standards of care. Ukraine legislation has actively developed in the last ten years, especially given the needs presented with the Ukrainian-Russian war. Ukrainian psycholo- gists-counselors address the needs of hundreds of thousands of recent veter- ans and displaced people that fled occupied territories. Therefore, the stand- ards of care and the need for an updated unified ethical code are actively dis- cussed in Ukraine at present. The purpose of this paper was to discuss universal principles of ethics that could be contextualized to update the Ukrainian eth- ics code for psychological counseling. The authors apply social dominance the- ory and the contextual model of psychotherapy to illustrate ethical guiding prin- ciples that need to be considered in the developing code of ethics. Case study examples are provided to illustrate global ethical principles application with the cultural sensitivity and respect for the global environment. The paper concludes with concluding social implications to ethical practice within Ukraine and gui- dance for future research

Вісник Харківського національного університету

The adsorption of reduced forms of molybdo-phosphoric, molybdo-antimono-phosphoric and molybdosilicic heteropoly acids with few anion-exchanger on the base of tetradecylammonium nitrate absorbed onto amorphous silica was investigated. The interaction of heteropoly acids with immobilized quaternary ammonium salts was investigated via UV/VIS and solid-phase spectrophotometric methods. The significant influence of the surface groups on the chromophorous system of adsorbed heteropoly anions was shown. Unexpected strong fixing of HPA on the surface was found to be a result of formation of ion associates between heteropoly acids and immobilized tetradecylammonium nitrate and HPA interaction with active groups of the nonmodified silica surface

Platinum surface complexes as precursors for H–O recombination catalysts

In this work, the adsorption of platinum (II, IV) chloride complexes from acidic solutions on silica gel modified with quaternary ammonium salts (QAS) was studied. The uptake of the platinum chloride complexes is caused by the formation of ionic (QAS + ) 2 [PtCl x ] 2− ( x  = 4, 6) associates on the surface of silica gel. The isotherms of adsorption are fitted by the Langmuir model. The maximum capacity for [PtCl 4 ] 2− and [PtCl 6 ] 2− is 0.99 and 1.13 mmol/g, correspondingly. The respective adsorption constants K L  = 6.8 and 10 × 10 5  l/mol prove the high affinity of the adsorbates to the QAS-modified surface. Platinum metal nanoparticles supported on the surface of the silica gel were prepared by reducing the adsorbed platinum (II, IV) complexes. Such nanoparticles functioning at the moderate temperature regime have demonstrated a reasonable catalytic activity for the hydrogen and oxygen recombination, and an excellent stability over 35 cycles of the reaction

2,6-Diamino-1--methylpyrimidine as new fluorescent probe for palladium(II) determination using hyphenated technique

The selective and sensitive hyphenated technique for Pd(II) fluorescence and spectrophotometric determination was proposed. The procedure was based on preliminary solid-phase extraction of [PdCl 4 ] 2− onto silica modified with quaternary ammonium salts, with the subsequent elution from the surface by 2,6-diamino-1- N -methylpyrimidine solution and measurement of the fluorescence intensity. The luminescence enhancement effect of 2,6-diamino-1- N -methylpyrimidine in the presence of Pd(II) due to the complex formation was applied to the development of sorption-spectroscopic techniques for detecting trace amounts of palladium in solution