The effect of sample preparation on metal determination in soil by FAAS

Different methods for the determination of several metals in soils by flame atomic absorption spectrometry (FAAS) were investigated. Different procedures for total dissolution of soil: I – HF+HClO₄, H₃BO₃, HCl digestion (conventional heating), II – HF+HClO₄, H₃BO₃ digestion followed by fusion with LiBO₂ (conventional heating) and III – HF+HCl+HNO₃, H₃BO₃ digestion (microwave heating), as well as a leaching procedure with HNO₃+HClO₄, HCl were tested and compared. For quality assessment, the certified reference material S-1 soil was used. For most of the investigated metals, the best accuracy and precision were achieved when the procedure I or III were used. The developed procedure was applied to the analysis of soil samples from crude oil refinery and dump of petroleum origin wastes regions.     

Preparation and study of rare earth 4-aminosalicylates

Summary p-Aminosalicylates of Y, La and lanthanides prepared in the reaction of the ammoniump-aminosalicylate and lanthanide chlorides in solutions have the general formulaLn(C₇H₆O₃N)₃·nH₂O, wheren=3 for La, Ce;n=2 for Pr, Nd, Sm, Eu;n=0 for Y, Gd—Lu. Their solubilities in water are of the order of 10^–3 mol dm^–3. Heating above 350–450 K leads to dehydration and decomposition at the same time. The IR and X-ray spectra for the obtained complexes were recorded. It was found that only complexes of La—Nd are crystalline compounds. The way of metal-ligand coordination is discussed.

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Darstellung und Charakterisierung der Komplexe von Seltenen Erdmetallen mitp-Aminosalicylsäure

Zusammenfassung Zur Darstellung der Verbindungen des TypsLn(C₇H₆O₃N)₃·nH₂O (mitn=3 für La, Ce;n=2 für Pr, Nd, Sm, Eu;n=0 für Y, Gd—Lu) wurde die berechnete Menge von Ammonium-p-aminosalicylat undLnCl₃-Lösungen beipH5.8 gemischt und zur Kristallisation gebracht. Ihre Wasserlöslichkeit bei 298 K ist in der Größenordnung 10^–3 mol dm^–3. Beim Erhitzen erfolgt bei 350–450 K Entwässerung und Zersetzung zugleich. Die Infrarot- und Röntgenspektren der erhaltenen Komplexe wurden gemessen und dabei festgestellt, daß nur die La—Nd-Komplexe kristalline Verbindungen sind. Die Art der Koordination der Seltenerdmetalle mit den Liganden wird diskutiert.

     

Highly enantioselective photocyclization of 1-alkyl-2-pyridones to beta-lactams in inclusion crystals with optically active host compounds

[reaction: see text] Upon photoirradiation of a 1:1 inclusion complex of (-)-3 and 2-alkyl-1-pyridone (1) (R = Et, n-Pr, i-Pr, n-Bu, i-Bu) in the solid state, optically active beta-lactams (2) of 91-99.5% ee were obtained in good yield.     

Correlation between thermodynamic properties and coordination states of aqueous bivalent transition metal sulfates

The osmotic coefficients for CoSO₄, NiSO₄, CuSO₄, MnSO₄, and ZnSO₄ have been found to be approximately the same up to very highest concentrations, while they are significantly higher for MgSO₄. Negligible changes in the visible spectra of CoSO₄ and NiSO₄ induced by increasing concentration indicate little, if any, coordination of the sulfate anion, while the UV spectral effects indicate outer-sphere association. More distinct spectral effects are observed for CuSO₄. However, the free sulfate anion concentration is found to be the same in equimolal solutions of CoSO₄, NiSO₄, and ZnSO₄, and probably also in CuSO₄, while it is higher in the solutions of MgSO₄. The conclusion is drawn that the four isopiestic transition metal sulfates at any given molality are in corresponding coordination states. The general problem of correlation between thermodynamic properties of solutions and the coordination states of the dissolved salts is discussed.     

Complexes of Y,La, and lanthanides withm-aminobenzoic acid

Summary m-Aminobenzoates of Y, La and lanthanides prepared in the reaction of the hydroxides of metal withm-aminobenzoic acid in solution have the general formulaLn(m-C₆H₄NH₂COO)₃·nH₂O wheren=4 for Ho, Tm,n=5 for Y, Sm, Dy, Er, Lu, andn=6 for La-Nd, Eu, Gd, Tb, Yb. The water molecules in the hydrated compounds are in the outer coordination sphere. On heating in air at 350–410 K dehydration occurs and anhydrousm-aminobenzoatesLn(m-C₆H₄NH₂COO)₃ are formed. On the basis of the IR spectra it was found that the metal in hydratedm-aminobenzoate of lanthanides is simultaneously coordinated through amino- and carboxyl groups whereas in anhydrousm-aminobenzoates of lanthanides only trough the bidentate carboxyl group. From X-ray analysis it was stated that the hydratedm-aminobenzoates of lanthanides are isostructural in the whole range Y, La-Lu.

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Komplexe von Y, La und Lanthaniden mitm-Aminobenzoesäure

Zusammenfassung Zur Darstellung der Verbindungen des TypsLn(m-C₆H₄NH₂COO)₃·nH₂O (mitn=4 fürLn=Ho, Tm,n=5 fürLn=Y, Sm, Dy, Er, Lu undn=6 fürLn=La-Nd, Eu, Gd, Tb, Yb) wurde die berechnete Menge vonLn(OH)₃ undm-C₆H₄NH₂COOH-Lösung bei 363 K gemischt und zur Kristallisation gebracht. Die Produkte wurden abfiltriert, mit Alkohol gewaschen und bis zur Gewichtskonstanz getrocknet. Die VerbindungenLn(m-C₆H₄NH₂COO)₃·nH₂O sind isostrukturell, mit geringer Löslichkeit in Wasser bei Raumtemperatur. Beim Erhitzen erfolgt zunächst Entwässerung bei 350–410 K, später bei 600–1 050 K unter Zersetzung zu CeO₂, Pr₆O₁₁, Tb₄O₇ undLn ₂O₃. Die Infrarotspektren der Verbindungen wurden registriert. Es wurde festgestellt, daß die Koordination der Seltenerdmetalle mit den Liganden sowohl durch Amino- als auch mit Carboxylgruppen erfolgt.

     

Calorimetric characterization of 2′,3′-dideoxyinosine water solution

A study of 2′,3′-dideoxyinosine (ddI) stability and its interaction with human serum albumin (HSA) was carried out by differential scanning microcalorimetry DSC. Scan rate dependent and irreversible endothermic thermal degradation of ddI was analyzed with use of kinetic approach. Observed process could be interpreted in terms of simple first-order one step kinetic model. Moreover it was shown that ddI bound weakly to the human serum albumin and stabilized this protein.     

Photo‐Induced Hydrogen Exchange Reaction between Methanol and Glyoxal: Formation of Hydroxyketene

We study the structure and photochemistry of the glyoxal–methanol system (G–MeOH) by means of FTIR matrix isolation spectroscopy and ab initio calculations. The FTIR spectra show that the non‐hydrogen‐bonded complex, G–MeOH‐1, is present in an inert environment of solid argon. MP2/aug‐cc‐pVDZ calculations indicate that G–MeOH‐1 is the most stable complex among the five optimized structures. The interaction energy partitioned according to the symmetry‐adapted perturbation theory (SAPT) scheme demonstrates that the dispersion energy gives a larger contribution to the stabilization of a non‐hydrogen‐bonded G–MeOH‐1 complex than compared to the hydrogen‐bonded ones. The irradiation of G–MeOH‐1 with the filtered output of a mercury lamp (λ>370 nm) leads to its photo‐conversion into the hydroxyketene–methanol complex HK–MeOH‐1. The identity of HK–MeOH‐1 is confirmed by both FTIR spectroscopy and MP2/aug‐cc‐pVDZ calculations. An experiment with deuterated methanol (CH₃OD) evidences that hydroxyketene is formed in a photo‐induced hydrogen exchange reaction between glyoxal and methanol. The pathway for the photo‐conversion of G–MeOH‐1 to HK–MeOH‐1 is studied by a coupled‐cluster method [CR–CC(2,3)]. The calculations confirm our experimental findings that the reaction proceeds via hydrogen atom exchange between the OH group of methanol and CH group of glyoxal.     

Synthesis, structural studies and reactivity of vanadium complexes with tridentate (OSO) ligand

The direct reaction between [VCl(3)(thf)3] or [VO(OEt)3] and 2,2'-thiobis{4-(1,1,3,3-tetramethyl-butyl)phenol (tbopH(2)) leads to the formation of [V(2)(micro-tbop-kappa(3)O,S,O)2Cl(2)(CH(3)CN)(2)] (1).4CH(3)CN or [V(2)(micro-OEt)2(O)2(tbop-kappa(3)O,S,O)2] (2), respectively, in high yield. Compounds 1 and 2 were characterized by chemical and physical techniques including X-ray crystallography and variable temperature magnetic susceptibility studies (J = -29.1 cm(-1)) for 1. Complexes 1 and 2 were supported on MgCl2 and when activated with aluminium alkyls, were found to effectively polymerize ethene to produce polyethylene with a narrow molecular weight distribution M(w)/M(n) approximately 3.     

Use of hop cone extract obtained under supercritical CO2 conditions for producing antibacterial all-purpose cleaners

This paper attempts to demonstrate empirically the possibility of using a hydrophobic extract of hop cone obtained under the conditions of supercritical carbon dioxide to produce all-purpose cleaner with antimicrobial activity and low irritant potential. A series of prototypes of products varied by the extract concentration was developed. The formulations were assessed for physicochemical properties: particle size, turbidity, and color. The results indicate that the hydrophobic extracts of hop cone can be a valuable component of chemical products intended for washing, having a broad spectrum of action and contributing to improvement of the product’s safety.     

Moments and Mellin transform of the asset price in Stein and Stein model and option pricing

In this paper, we derive closed formulas for moments and Mellin transform of the asset price in the stochastic volatility Stein and Stein model. Next, we present applications of our results to pricing power and self-quanto options using numerical methods.