Fine-powder Al2O3 and SiO2 for preparation of multielement standards for rare-earth element analysis

The present paper based on experimental results contains discussions and suggestions on the possible use of fine-powder Al₂O₃ and SiO₂ with their original content of microimpurities of up to 40 elements, as multielement standards for neutron activation analysis. For example, activation analysis of As, Au, Ba, Cr, Cs, Fe, Ga, K, Ni, Sb, Sc, Se, Sr, Ta, Th, Ti, U, W, Zn, Zr and the REE La, Ce, Nd, Sm, Eu, Tb, Tm, Yb contained in SiO₂ powder off MERCK reagents showed their concentrations to be 0.1 to 5% of those in IAEA standard SL-1. In Al₂O₃ this level is even lower, approximately 10 times and more for the majority of the above-mentioned elements. As Al₂O₃ and SiO₂ are good sorbents for the majority of elements, additional introduction of some elements may allow more methods of analysis. The homogeneity of Al₂O₃ and SiO₂ samples both in the original state and after introduction of some elements was determined by neutron activation analysis, and the SD did not exceed 1% for an Al₂O₃ sample weight of 0.1 g, and 2% for SiO₂.     

Thermodynamic behavior of poly(3-alkyl thiophene) blends: Equilibrium cocrystal formation and phase segregation

The equilibrium cocrystal formation of poly(3-alkyl thiophene) (P3AT) blends has been studied by isothermal cocrystallization in a differential scanning calorimeter (DSC-7). The equilibrium melting points (T(m)0) of the cocrystals are measured using the Hoffman-Weeks extrapolation procedure. The equilibrium phase diagrams are of three different types: (a) concave upward, (b) linear, and (c) linear with phase separation at higher content of lower melting component. The phase diagram nature depends on the regioregularity difference and also on the difference in the number of carbon atoms in the pendent alkyl group of the components. The origin of biphasic nature of type "c" phase diagram has been explored from the glass transition temperature (Tg) measurement using a dynamic mechanical analyzer. The biphasic compositions show two glass transition temperatures (Tg) as well as two beta transition temperatures (T beta). The T(g)s of phase-separated regions correspond to almost the component values but the T(beta)s correspond to that of a lower (T beta) component value, and the other is higher than that of the higher (T beta) component value. Possible reasons are discussed from the interchain lamella thickness in the P3AT blends and molecular modeling using molecular mechanics program.     

Emission behavior of 1-methylaminopyrene in aqueous solution of anionic surfactants

A new fluorescent probe, methylamino derivative of pyrene, has been considered to characterize the concentration dependent emission behavior of an aqueous solution of anionic surfactants, viz., SDS, DSS, and SDBS. It was found that the emission of the probe is uniquely sensitive to the changes in surfactant (anionic) concentration due to the functional group effect of the probe over the parent moiety, pyrene. Here, 1-methylaminopyrene (MAP) showed significant quenching of emission well below the critical micellar concentration (cmc) of the surfactant. Excimer emission of the probe due to the formation of premicellar aggregates of the surfactant solutions at a concentration close to but below the cmc and again an enhanced emission of the probe above the cmc were observed as a consequence of definite MAP-surfactant interactions. These observations assisted the possible quantification ofsurfactant concentrations and their chain length dependent premicellar aggregate formations. Significant monomer emission in relation to probe distribution in micelle was analytically authenticated. Dynamic light scattering (DLS) studies revealed the incorporation of the probe molecules in the micellar core. The fluorophore emission showed nonlinear behavior when the surfactant concentration was far above the cmc. Abrupt changes in the emission characteristics in relation to the micellar concentration led to the determination of the cmc of the surfactants.     

Manganese(II) Silylamides

Mn[N(SiMe₃)₂]₂(THF) ( I ) (Me = methyl, THF = tetrahydrofuran) was obtained on large scale from “active” MnCl₂ and LiN(SiMe₃)₂ in THE in 85–93% yield. The novel, theoretically interesting tetra-coordinated Mn[N(SiMe₃)₂]₂L₂ series was derived from I , where L = THF, pyridine and t-butyleyanide. All these species are quite stable thermally and exhibit exteme oxygen sensitivity. Preparation, properties, and reactions of unsymmetrically substituted (“hemi”) X? Mn? Y type compounds are presented also, where X = ? Cl, ? NO₃ and n = butyl, and Y = ? N(SiMe₃)₂ and ? OR. From Cl? Mn? N(SiMe₃)₂, with or without coordinated THF being present, the unusual (Mn{SiMe₃)₂, was isolated as yellow crystals. The “hemi” Mn(II)-system exhibits only moderate thermal stability and tends to disproportionate. Many derivatives are photosensitive, especially with UV light.     

Mineral and microelement compositions of urinary stones

The mineral and microelement compositions of urinary stones from patients in various districts of the Novosibirsk region are analyzed. The mineral composition is determined using X-ray powder diffraction and vibrational spectroscopy. The microelement composition is identified using synchrotron radiation X-ray fluorescence analysis. Calcium oxalates (whewellite CaC₂O₄ · H₂O and weddellite CaC₂O₄ · 2H₂O) are the most frequent components of the urinary stones. Oxalate uroliths contain a variety of microelements in significant amounts. Phosphate uroliths, represented by hydroxylapatite Ca₅(PO₄)₃(OH) and struvite MgNH₄PO₄ · 6H₂O, account for about one-fifth of the collection. Apatite urinary stones contain maximal strontium amounts. The struvite uroliths have higher rubidium levels. Uric acid uroliths (C₅H₄N₄O₃) account for about 11% of the collection. Their strontium concentrations are minimal. The element composition of the urinary stones is a function of their mineral constituents, the environmental surroundings, and the metabolism specifics of the patient.     

Screening of urinary coproporphyrin using cloud point extraction and chemiluminescence detection

A simple screening test was developed for the sensitive and selective measurement of urinary coproporphyrin. In this screening test, efficient and selective extraction/pre-concentration of coproporphyrin from the aqueous medium(urine) into a much smaller volume phase containing a common non-ionic surfactant (Triton X-100) and ethyl acetate was accomplished by the addition of a relatively large amount of a cloud point depressing electrolyte (K(3)PO(4)) into the sample solution to effect cloud point separation. Sensitive and selective detection of coproporphyrin in the mixed Triton X-100 and ethyl acetate phase was performed via chemical excitation using the peroxyoxalate chemiluminescence reaction. The effects of surfactant and cations (from the cloud point depressing electrolyte) on the chemiluminescence intensity of coproporphyrin were briefly investigated. Furthermore, the spectrum of urinary coproporphyrin obtained using the present chemiluminescence method was briefly compared with that obtained from fluorescence method.     

Hydration layer of a cationic micelle, C(10)TAB: structure, rigidity, slow reorientation, hydrogen bond lifetime, and solvation dynamics

We report a theoretical study of the structure and dynamics of the water layer (the hydration layer) present at the surface of the cationic micelle decyltrimethylammonium bromide (DeTAB) by using atomistic molecular dynamics simulations. The simulated micelle consisted of 47 surfactant molecules (and an equal number of bromide ions), in good agreement with the pioneering light scattering experiments by Debye which found an aggregation number of 50. In this micelle, three partially positively charged methyl groups of each surfactant headgroup face the surrounding water. The nature of the cationic micellar surface is found to play an important role in determining the arrangement of water which is quite different from that in the bulk or on the surface of an anionic micelle, like cesium perfluorooctanoate. Water molecules present in the hydration layer are found to be preferentially distributed in the region between the three partially charged methyl headgroups. It is found that both the translational and rotational motions of water exhibit appreciably slower dynamics in the layer than those in the bulk. The solvation time correlation function (TCF) of bromide ions exhibits a long time component which is found to originate primarily from the interaction of the probe with the micellar headgroups. Thus, the decay of the solvation TCF is controlled largely by the residence time of the probe in the surface. The residence time distribution of the water molecules also exhibits a slow time component. We also calculate the collective number density fluctuation in the layer and find a prominent slow component compared to the similar quantity in the bulk. This slow component demonstrates that water structure in the hydration layer is more rigid than that in the bulk. These results demonstrate that the slow dynamics of hydration layer water is generic to macromolecular surfaces of either polarity.     

New routes to condensed polynuclear compounds—VIII : Scope of phenanthridine synthesis through cyclisation of haloanils

The new phenanthridine synthesis based on reaction of haloanils with metal amides is of wide application. The cyclisation succeeds in presence of alkyl, alkoxy, dialkylamino, cyano, carboxy, halogeno and carbonyl groups but fails in case of nitro substituents.     

Microwave-assisted synthesis of novel imidazolium-based ionic liquid crystalline dimers

Microwave promoted synthesis of novel imidazolium-based ionic liquid crystalline dimers containing calamitic-calamitic, calamitic-discotic and discotic-discotic moieties is reported. Classical reactions failed to produce these dimers. The thermotropic liquid crystalline properties of these salts were investigated by polarizing optical microscopy, differential scanning calorimetry and X-ray diffractometry. These salts, except the one having calamitic-discotic units, with bromide as counter ion were found to be mesomorphic over a wide temperature range.     

The first X‐ray structure of a hexa­ammine­cobalt(III) salt with two different complex chloro­cadmium anions: synthesis,characterization and crystal structure of [Co(NH3)6]4[CdCl6][CdCl4(SCN)(H2O)]2Cl2·2H2O

In the title complex salt, tetra­kis[hexa­ammine­cobalt(III)] hexa­chloro­cadmate(II) bis­[aqua­tetra­chloro­thio­cyanato­cad­mate(II)] dichloride dihydrate, the discrete ions, i.e. [Co(NH₃)₆]³⁺, Cl⁻, [CdCl₆]⁴⁻ (located on an inversion centre) and [CdCl₄(SCN)(H₂O)]³⁻, together with cocrystallized water mol­ecules, are assembled by means of a network of hydrogen‐bonding inter­actions. This is the first X‐ray structure determination of a hexa­amminecobalt(III) salt with two different complex chloro­cadmium anions.