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RIP-Pd-Test reagent indicator paper based on 1-phenyl-5-(3,4-dihydro-6-methyl-4-oxo-3H-pyrimidin-2-yl)-formazan-6-cellulose has been proposed for determining the palladium content using the sorption-reflectometry and visual-test methods in objects of complex composition. The RIP synthesis technique was described. The estimated composition of the metal complex formed as a result of the heterogeneous indicator reaction at pH 1.5–2.5 was indicated, and the forced coordination of palladium : reagent = 1:1 was ensured. When the RIP interacted with palladium (II) ions, the yellow indicator strip became green with different intensities. Under the selected conditions, the high selectivity for the detection and determination of Pd(II) was shown. With the help of the «Ecotest-2040» portable reflectometer, the reflectometry measurements were carried out using the red LED with the radiation wavelength of 660 nm. For the visual testing, the color scales were used. The indicator reaction was proposed to be carried out in three modes: without concentration and with concentration of the test solution in 100 and 1000 times on the reaction indicator zone of the paper strip (using the pocket pumping device). By the statistical method, the limit of Pd(II) determination for the visual test method (40, 0.47, 0.042 mg/l) was estimated. The palladium detection limit using the reflectometer (19, 0.22, 0.018 mg/l) for the three modes, respectively, was calculated by 3s criterion. The found values of the limiting concentrations were comparable with the metrological characteristics of the known analysis methods in which solid-phase reagents were used. The trueness of the palladium determinations in technological objects of complex composition and drugs has been proven by the independent methods - atomic emission, spectrophotometric and gravimetric methods of analysis. The value of the relative standard deviation of the determined Pd(II) concentration using the portable reflectometer did not exceed 7%. Keywords: palladium(II), formazan, reagent indicator paper, sorption, reflectometry, visual test analysis DOI: http://dx.doi.org/10.15826/analitika.2020.24.2.007 V.M. Ostrovskaya 1 , E.A. Reshetnyak 2 , O.S. Chernyshova 3 , E.Yu. Bryleva 3 1 25 State research institute of the Ministry of Defence of Russian Federation" , 10 Molodogvardeyskaya St r. , Moscow , 121467, Russia n Federation 2 V.N. Karazin National University, 4 Svoboda Sq., Kharkiv, 61022 , Ukraine 3 SSI "Institute for Single Crystals" NAS of Ukraine, 60 Nauky Ave, Kharkiv, 61072 , Ukraine

Sm3+, Pr3+ and Dy3+-doped Ca3Nb1.6875Ga3.1875O12 - CNGG and Ca3Li0.275Nb1.775Ga2.95O12 - CLNGG crystals are of interest as solid-state laser materials emitting in the yellow-orange spectral range, especially for diode pumping due to their partially disordered nature. In this work, for the first time to our knowledge, single crystals of Sm, Pr and Dy-doped CNGG and CLNGG crystals were grown by the Czochralski method. For the doping of CNGG and CLNGG crystals, five new stoichiometric garnets were synthesised by solid-state reaction method: praseodymium-gallium-garnet (PrGG), dysprosium-gallium-garnet (DyGG) and praseodymium-lithium-niobium-gallium-garnet (PrLNGG), samarium-lithium-niobium-gallium-garnet (SmLNGG), and dysprosium-lithium-niobium-gallium-garnet (DyLNGG). Samarium-gallium-garnet (SmGG) was also sintered and used for the doping of Sm:CNGG crystal. Structural properties of sintered materials and grown crystals were investigated by X-ray diffraction and the chemical compositions of the grown crystals were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) method. The spectroscopic investigations of the grown crystals have shown that they are promising laser materials in the yellow-orange spectral range.

Spectroscopic investigation of Dy3+ doped Ca3(Nb,Ga)5O12 (CNGG) and Ca3(Li,Nb,Ga)5O12 (CLNGG) single crystals were performed in order to assess their potential as laser materials for yellow emission. Dy:CNGG and Dy:CLNGG single crystals were grown by the Czochralski method and investigated by high-resolution spectroscopic measurements for the first time. The Judd-Ofelt intensity parameters for the f-f transitions of Dy3+ in CNGG and CLNGG single crystals, were used to determine radiative transition rates Ar, branching ratios β, and radiative lifetime τr of the fluorescent Dy3+ levels. Based on low temperature absorption and emission spectra, partial energy levels diagram of Dy3+ doped CNGG and CLNGG single crystals were obtained. The emission cross-sections for the 4F9/2 → 6H13/2 transition of special interest for laser application were determined. The room temperature decay curves were analyzed through the framework of Inokuti–Hirayama (I-H) model and the results shows that electric dipole-dipole interaction are responsible for the energy transfer processes between Dy3+ ions in CNGG and CLNGG single crystals.

MnO(OH) particles were produced by reacting KMnO4 with MnCl2 in an alkaline medium. It was found that the specific surface area of MnO(OH) particles grows within the range 160–360 m2 g–1 as temperature is lowered and the total concentration of manganese in solution decreases. The extraction efficiency of Ce, Eu, Co, and Sr metals from aqueous solutions was studied. IT was shown that the degree of extraction of all the metals exceeds 90% at pH 3–9. The specific surface area has no significant effect on the sorption capacity for Ce, Eu, and Sr, which is 100, 49, 45 mg g–1 at pH 5, respectively. The sorption capacity for cobalt (pH 6.5) grows with the specific surface area increasing from 20 to 32 mg g–1.

We have studied the sorption of Eu(III) ions on Merrifield resin (chloromethylated polystyrene) impregnated and covalently modified with tetrahydroxythiacalix[4]arenes that contain hydrogen atoms, tertbutyl, and dialkoxyphosphonylmethyl moieties on the macrocyclic upper rim. The resulting materials have a sorption capacity of up to 70 mg/g and allow one to extract up to 99% of Eu(III) from aqueous solutions with medium mineral content at pH 5.5–6.

An effect of nature of anions (NO3−, Cl−, HCO3−) present in the solution of deposition on the particle formation of Fe2O3 was investigated. It was established that from nitrate solutions large shapeless agglomerates (50–200 μm) are formed, which are composed of spherical particles (specific surface Ssp = 150 m2 g−1). Introduction of chloride ions leads to the formation of cubic and oval dense particles with size of about 0.12–0.20 μm (Ssp = 30 m2 g−1). An efficiency of extraction of metals from aqueous solutions was examined. The metals under study can be arranged relative to pH50 in a series: Eu3+ > Ce3+ > Cu2+ > Zn2+ > Cd2+ > Co2+ > Mn2+ > Sr2+. It was found that the sorption capacity of the synthesized Fe2O3 particles with respect to the copper is 15.6 (Ssp = 150 m2 g−1) and 9.2 mg g−1 (Ssp = 30 m2 g−1).

Electrochemical behavior of vinpocetine at a plain carbon paste electrode and paste electrodes modified with different calixarenes and ammonium metavanadate was studied by means of cyclic and differential pulse voltammetry. The effect of pH and scan rate on the response at both plain and modified carbon paste electrodes has been revealed. Modification of an electrode with a mixture of ammonium metavanadate and some calixarenes led to considerable decrease of background current along with sensitivity increase as compared to an unmodified carbon paste electrode or an electrode modified with calixarenes only. For the most effective electrode composition, the linear working range was shown to be 2 . 10 −8 ‐6 . 10 −6 M with a detection limit of 5 . 10 −9 M.

Effects of temperature, concentration of thiourea and reaction conditions (thermal heating and microwave irradiation) on morphological properties of ZnS particles obtained by sedimentation from 0.01, 0.1 and 1 М zinc nitrate solutions are studied. It is found that ZnS particles of two shapes are formed from thiourea solutions at a thermal heating (70–90 °С): agglomerated particles of the spherical shape with the dimensions of agglomerates 50–100 nm (particle size in agglomerates of 3–5 nm) and hexagonal columns in length up to 2 μm and diameter of 80–100 nm. At the microwave heating conditions (90 °С), irrespective of thiourea concentration formation of spherical ZnS particles with the size 0.6–1.2 μm is observed.

Inductively coupled plasma atomic emission spectrometry (ICP-AES) and flame spectrometry are used to establish the stoichiometric composition of Li6Gd(BO3)3, Li5.4Na0.6Gd(BO3)3, LaB3O6, and SrB4O7 single crystals, including cerium-doped crystals. It is shown that flame spectrometry is more advantageous for analysis of pure borate crystals. ICP-AES is more universal and allows determining basic elements and admixtures independently of solvents used for decomposition of borate samples. Both methods provide sufficient accuracy of the analysis.

Solubility products of CdO (pKs,CdO = 6.80 ± 0.2), ZnO (pKs,ZnO = 10.0 ± 0.5), NiO (pKs,NiO = 11.2 ± 0.2) and EuO (pKs,EuO = 13.1 ± 0.2) in molten CsI at T = 973 K are determined by potentiometric titration of (0.02 to 0.03) mol · kg−1 solutions of the corresponding metal chlorides by strong base (KOH) using a membrane oxygen electrode Pt(O2)|ZrO2(Y2O3) as an indicator. On the basis of pKs,MeO values, all the oxides studied are referred to practically insoluble in molten CsI. The values of the oxide solubility in CsI melt are lower than the corresponding values in molten alkali metal chlorides. This can be explained by ‘softer’ basic properties of I– as compared with Cl– in the frames of the Pearson ‘hard’ and ‘soft’ acid–base concept. In the oxide samples studied, the values of the solubility fall with the decreasing cation radius. The correlation between pKs,MeO and the polarizing action by Goldshmidt ( Zr Me 2 + - 2 ) of the cation is practically linear and may be proposed for estimation of the solubility of s- and d- element oxides in molten CsI on the basis of their cation radii.

A procedure is suggested for determining the distribution constants of methyl orange dye between water and direct microemulsion droplets (N-cetylpyridinium chloride + 1-pentanol + benzene in water) as the disperse phase, which allows one to circumvent difficulties associated with the formation of low-solubility salts and premicellar associates. Within the framework of the pseudophase model of equilibria, the distribution constants of the yellow monoanion and red zwitterion methyl orange forms between microscopic droplets and the continuous phase at an ionic strength of 0.2 mol/l (NaCl + HCl) were determined from the dependence of the apparent ionization constant of the indicator on the volume fraction of the disperse pseudophase. The constants on the molar concentration scale were \( P_{B^ - }^ \otimes \) = (253 ± 0.08) × 105 and \( P_{^ + HB^ - }^ \otimes \) = (1.7 ± 0.4) × 102.