An ion-imprinted thiocyanato-functionalized mesoporous silica for preconcentration of gold(III) prior to its quantitation by slurry sampling graphite furnace AAS

A gold(III)-imprinted thiocyanato-functionalized silica network of type SBA-15 was prepared by co-condensation of tetraethoxysilane (TEOS) with thiocyanatopropyltriethoxysilane (TCTES) in the presence of Pluronic123 and Au(III) ions. Compared to the non-imprinted material, the imprint has a higher selectivity and adsorption capacity for Au(III). The maximum static adsorption capacity for Au(III) is 475 mg·g^?1 for the ion-imprinted, and 62 mg·g^?1 for the non-imprinted sorbent. The imprint was applied to the sorption of Au(III) from digested geological samples prior to its determination by graphite furnace atomic absorption spectrometry. Adsorption is fast and does not substantially prolong the analytical procedure. Under optimum conditions, the detection limit for Au(III) is 2 ng·g^?1. The method was validated by analyzing certified reference materials, and results were in good agreement with certified values. The procedure was successfully applied to the separation and determination of gold in complex geological samples.

Open image in new window

Graphical abstract Schematic presentation of the preparation of ion-imprinted thiocyanato-functionalized mesoporous silica and its application for the preconcentration of gold from digested soils before its determination by slurry sampling graphite furnace atomic absorption spectrometry (GF AAS).

     

E-optimality of some row and column designs

In this paper we consider experimental settings where treatments are being tested in b ₁ rows and b ₂ columns of sizes k _1i and k _2j , respectively, i=1,2,..., b ₁, j=1,2,..., b ₂. Some sufficient conditions for designs to be E-optimal in these classes are derived and some necessary and sufficient conditions for the E-optimality of some special classes of row and column designs are presented. Examples are also given to illustrate this theory.     

Properties of hydration shells of protein molecules at their pressure- and temperature-induced native-denatured transition.

Properties of water at the surface of biomolecules are important for their conformational stability. The behaviour of hydrating water at protein transition (t) pressures P(t) and temperatures T(t) , with the points (P(t),T(t) ) lying in the Native-Denatured (N-D) transition line, is studied. Hydration shells at the hydrophilic regions of protein molecules with surface charge density sigma are investigated with the help of the equation of state of water in an open system. The local values of sigma rather close to each other (sigma(D) approximately 0.3 C m(-2)) are found for six different experimental lines of the N-D transition found in the literature. The values sigma(D) correspond to the crossings of the total pressure (P(t)+Pi) vs sigma isotherms at different T(t) (Pi-electrostriction pressure). The pressures P(t) and temperatures T(t) appear to be related with some selected sites at the surfaces of the protein molecules.     

Crystal structure of 7-cyano-6,7-dimethyl-1-phenyl-1,3,6,7-tetrahydro-2,1-benzoxaphospole 1-oxide

The crystals (C₁₆H₁₈NO₂P,M _r=287.30) are orthorhombic, space group Pbca witha=8.200(2),b=14.857(2), andc=24.396(5)Å,V=2972.1 ų,Z=8,D _x=1.284 mg m^–3,(MoK)=0.71069 Å,=1.90 cm^–1,F(000)=216,T=295K. FinalR=0.044 for 1673 observed reflections collected on a diffractometer. Structure solved by direct methods.Cis-junction and double bond in the six-membered ring cause its almost ideal sofa conformation. The two neighboring methyl groups are cis, and cyano substituent is in an equatorial position. There is a shortintramolecular H(o-phenyl)O(endocyclic) contact of 2.53(3)Å and the phenyl ring is in a less favorable rotational orientation due to molecular packing.     

Conformational mobility in chemically-modified cyclodextrins

The observation that per-2,6-O-methyl-3-O-benzoyl--cyclodextrin (1) displays some unusual conformational behaviour in solution has led to a detailed investigation by (dynamic) NMR spectroscopy of the equilibration process that occurs in solutions of per-2,3-O-benzoyl--cyclodextrin (3) and some related compounds (7–9) between conformational isomers with averagedC ₆ andC ₃ molecular symmetries in certain organic solvents such as benzene, dichloromethane, and chloroform. The solvent dependence of the conformational equilibrium is also reflected in a spread of values for the specific optical rotations for 3 from +9° in 1,1,2,2-tetrachloroethane, where there is a degenerate equilibrium between species withC ₃ molecular symmetry, to +92° in acetone where a species with averagedC ₆ symmetry is present.This paper is dedicated to the memory of the late Dr C. J. Pedersen.     

Polymerization of 1,3,5-trithiane in the solid state initiated by UV-irradiation. II. Investigation of the initiation process

The influence of the irradiation and polymerization atmosphere on polymer yield was observed. It was shown that in the initiation process oxygen presence is necessary. ESR studies of UV-and γ-irradiated 1,3,5-trithiane were done. The influence of the irradiation atmosphere on generated radicals and the influence of UV-action on radicals formed by γ-irradiation was also investigated. The possible initiation mechanism of cationic polymerization of 1,3,5-trithiane is discussed. A comparison of the 1,3,5-trithiane is polymerizations initiated chemically and by UV- or γ-irradiation is also given.     

Equivalence of two series of spherical representations of a free group

Summary The spherical principal series of a non-commutative free group may be analytically continued to yield a series of uniformly bounded representations, much as the spherical representations (in1/2) + it of SL (2,R) may be analytically continued in the strip 0 < Rez < 1. This series of uniformly bounded representations was constructed and studied by A. M.Mantero and A.Zappa. Independently T.Pytlik and R.Szwarc introduced and studied representations of the free group which contain a series of subrepresentations indexed by spherical functions. Both series consist of irreducible representations and include the spherical complementary series. The aim of this paper is to prove that the non-unitary uniformly bounded representations of the two series are also equivalent.     

Eigenvibrations of the expanding universe

A theoretical interpretation of the observed periodicity of large-scale (128 Mpc) correlations of galaxies is proposed as due to eigenvibrations of the closed expanding universe. Eigensolutions of the equations of motion for a scalar field in an inflationary model allow one to compute the energy density, interpreted as matter density. Isotropic eigensolution give rise to a matter density distribution having a periodic structure centered at the north pole of the closed Robertson-Walker universe represented by S³/Z₂. It is able to reproduce well the striking periodicity of the observational data, in the galactic north-south directions. The dipole and quadrupole eigensolutions and the location of the co-moving observer in a point of S³/Z₂ different from the center of the vibrational structure would imply, in a theoretically well predictable way, a decrease of the observed periodicity in some other directions.Partially supported by the State Committee for Scientific Research, Grant No. 2-0206-91-01.     

Potentiometric method for the determination of calcium in blood serum

A procedure for the determination of calcium in serum based on the complexation of calcium by a fixed amount of iminodiacetate at pH 9.6 with detection with a calcium-selective electrode is described. The effect of common concomitants was investigated; no interference was observed. When the procedure was tested on control sera, the bias was < 3% (6–8 replicate measurements); the relative standard deviation was < 5%.     

A simple method for determining the multilayer effects in adsorption of alcohols on silica gel

The excess adsorption isotherms ofn-pentanol, pentan-2-ol and 2-methylbutan-2-ol from binary and ternary solutions in benzene andn-heptane were measured. Experimental adsorption data are discussed in terms of a multilayer model of the surface phase. The main assumption of this model is that the surface layers being near the solid surface contain the molecules of the preferentially adsorbed component only. The phase-exchange reaction of molecules between bulk phase and last surface layer has been taken into account.On the basis of this theory it has been established for the investigated systems that the surface phase contains three molecular layers. Simultaneously appropriate surface phase capacities were determined.

---

Eine einfache Untersuchungsmethode für Mehrschicht-Effekte bei der Adsorption von Alkoholen an Kieselgel

Zusammenfassung Die Adsorptionsisothermen binärer und ternärer flüssiger Mischungen vonn-Pentanol, 2-Pentanol oder 2-Methyl-2-butanol in Benzol und/odern-Heptan wurden bezüglich Kieselgel gemessen. Die experimentellen Daten der Adsorption wurden mittels des Mehrschichts-Modells der Oberflächenphase diskutiert. Die Hauptvoraussetzung dieses Modells ist die Annahme, daß die Oberflächenschichten, die sich in der Nähe des Kieselgels befinden, nur Moleküle der bevorzugt adsorbierten Komponente enthalten. Es wurde auch die Phasen-Austauschreaktion von Molekülen zwischen Phaseninnerem und der letzten Oberflächenschicht in Betracht gezogen.Auf der Basis dieser Theorie wurde für die untersuchten Systeme festgestellt, daß die Oberflächenphase aus drei Molekülschichten besteht. Außerdem wurden die ermittelten Volumina der Oberflächenphase berechnet.