The ortho effect in the mass spectra of ortho/para isomers of bisphenol a derivatives and related compounds

New examples of the ortho effect in bisphenol A derivatives including interaction of the hydrogen of the ortho-hydroxy group with the neighbouring aromatic ring have been observed. The characteristic ions [M ? PhOH]^+middot; (m/z = 134) and [M ? CH₃ ? PhOH]⁺ (m/z = 119) were shown to form through the hydrogen transfer from hydroxy and isopropyl groups, respectively. The spectra of cyclic derivatives having ortho-hydroxy functions show [M ? 43]⁺, [M ? C₈H₉O]⁺, m/z = 147, m/z = 135 and [M ? C₉H₁₀O]⁺ ions. The proposed mechanims of the corresponding transformations were supported by mass spectra of deuterated analogues, methyl and trimethyl silyl ethers.     

NMR determination of enantiomeric composition of 1-substituted 3-amino-1,2-dicarba-closo-dodecaboranes using Eu(hfc)3

Experimental conditions for determination of enantiomeric composition of 1-substituted 3-aminocarboranes by ¹H and ¹³C NMR spectroscopy using chiral shift reagent Eu(hfc)₃ have been found.     

Fractionation of metals and metalloids by chemical bonding from particles accumulated by electrostatic precipitation in an Argentine thermal power plant

A study was undertaken to evaluate the distribution of Al, As, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn in fly ashes collected in the electrostatic precipitator of a thermal power plant in San Nicolás (Argentina). Five samples were collected during one week of operation. For the fractionation, the scheme applied consisted in extracting the elements in four fractions namely (i) soluble and exchangeable elements; (ii) carbonates, oxides and reducible elements; (iii) bound to sulfidic metals; and (iv) residual elements. Metals and metalloids at μg g^− 1 level were determined in each fraction by inductively coupled plasma optical emission spectrometry (ICP OES). For validation, a standard reference material (SRM 1633 coal fly ash) from NIST was subjected to the same chemical sequential extraction procedure that the samples. X-ray diffraction powder (XRD) analysis and scanning electron microscopy (SEM) were used to characterize the major minerals present in the matrix. Total analyte concentration (in μg g^− 1) varied from 10.6 for Pb to 17,622 for Al. Minimum and maximum concentrations (in μg g^− 1) found in individual samples in the four fractions were: Al, 92.7–9668; As, < 0.3–143; Cr, 2.0–10.4; Cu, < 0.2–35.6; Fe, < 0.3–4992; Mn, < 0.1–128; Ni, < 0.3–139; Pb, < 0.5–9.1; Ti, < 0.3–2243; V, 17.0–112.9; and Zn, < 0.1–68.2. The leachability of the 11 elements under study proved to be different. Low percentages of Al (1%), V (7%) and Cr (8%) were detected in the most bioavailable fraction. Arsenic was found to be most abundant in the non-silicate phase, represented by the second and third fractions, while Cr, Fe, Ni, Pb and Zn were mostly associated to the residual fraction.     

Determination of metal concentration in fat supplements for swine nutrition by atomic absorption spectroscopy

The presence of some essential and toxic metals in fat supplements for swine diet was investigated. Collected samples represented a relevant production of the Italian industry. In particular, some samples were enriched with antioxidants or waste cooking oils. The method for the determination of Ca, Cu, Cd, Fe, Mg, Mn, Ni, Pb, and Zn in fat samples was developed by means of a certified reference material (CRM 186) and a representative fatty sample (RFS). All samples were digested in closed vessels in a microwave oven and then analyzed by flame atomic absorption or graphite furnace atomic absorption spectrometry. The entire analytical method provided a satisfactory repeatability and reproducibility confirmed by agreement between the experimental recovery data obtained for the CRM 186 sample and, with the method of standard additions, for the RFS material. The samples generally showed a small amount of metals compared with the recommended daily intake for the essential elements. On the other hand, some samples contained a significant concentration, from an analytical point of view, of Cd, Ni, and Pb. Principal component analysis (PCA) was applied to inspect the experimental data obtained from samples analysis. Basically no differences were detected in terms of metal concentration among the fat supplements analyzed.     

Complexing processes in M(II)-dithiomalonamide-diacetyl triple systems (M= Ni,Cu) in ethanol solution and in a metal(II)hexacyanoferrate(II) gelatin-immobilized matrix materials

The complexing processes in the M ^II -dithiomalonamide-diacetyl triple system (M=Ni, Cu) occuring in the nickel(II)- and copper(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous alkaline solutions (pH~12) containing dithiomalonamide and diacetyl at room temperature, and between MCl₂, dithiomalonamide and diacetyl in EtOH solutions upon heating to$80°C, have been studied. In the Ni ^II -dithiomalonamide-diacetyl system, template synthesis occurs in EtOH solution but does not occur in the gelatin-immobilized matrix, whereas in the Cu ^II -dithiomalonamide-diacetyl system, template synthesis occurs in the gelatin-immobilized matrix but not in EtOH solution. Dithiomalonamide and diacetyl are the ligand synthons in the processes indicated.     

Blood lead monitoring in Italy: Assessment of the quality of results obtained between 1992 and 1994

Between 1992 and 1994, a new screening campaign for blood Pb monitoring in the Italian general population was carried out. Since the first campaign (started in 1978, in accomplishment of the European Community Directive 77/312/EEC) a working group of the Laboratory of Clinical Biochemistry at the Italian National Institute of Health (Istituto Superiore di Sanità), as the Reference Centre (RC), has coordinated the activity of various laboratories spread over the national territory. Appropriate quality assurance procedures, including an external quality assessment scheme (EQAS), were elaborated. Within the EQAS, three or four trials were carried out every year. Each laboratory participating in the trial analyzed eight control samples prepared from cow blood at different Pb concentrations. The results obtained by each peripheral laboratory and the RC between 1992 and 1994 have been compared by regression analysis. The same statistical method was adopted to compare the results obtained by each peripheral laboratory and the RC in the duplicate analysis of about 10 per cent of the human samples collected during the 1992–1994 monitoring campaign. There was no evidence of systematic differences between the regression lines obtained on control and human samples. In spite of the lower Pb concentration in the control samples analyzed during the 1992–1994 campaign, the analytical performance of the laboratories was better than that obtained in the previous screening campaign (1985–1986). Blood Pb levels observed in human samples collected between 1992 and 1994, confirm the downward time trend observed in the campaigns carried out in 1978–1979, 1980–1981 and 1985–1986. This study confirms that the results obtained in an EQAS are representative of the actual performance in the analysis of real (human) samples.     

Rigid optically-active D2 and D3 macrocycles

The synthesis and characterization of novel optically-active macrocycles, obtained by esterification reaction from a binaphthyl-containing diol and phthalic or terephthalic acids, and possessing overall D2 or D3 symmetry, is described.     

A general NMR method for rapid, efficient, and reliable biochemical screening

High-throughput screening is usually the method of drug-lead discovery. It is now well accepted that, for a functional assay, quality is more important than quantity. The ligand-based or protein-based NMR screening methodologies for detecting compounds binding to the macromolecular target of interest are now well established. A novel and sensitive NMR method for rapid, efficient, and reliable biochemical screening is presented. The method named 3-FABS (three fluorine atoms for biochemical screening) requires the labeling of the substrate with a CF(3) moiety and utilizes (19)F NMR spectroscopy for the detection of the starting and enzymatically modified substrates. The method allows for high-quality screening of large compound or natural product extract collections and for measuring their IC(50) values. Applications of this technique to the screening of inhibitors of the Ser/Thr kinase AKT1 and the protease trypsin are presented. In addition, an interesting application of 3-FABS to functional genomics is also presented.     

Structural characterization techniques for the analysis of semiconductor strained heterostructures

A combined method for structural characterization of strained epitaxial heterostructures involving different techniques such as Rutherford backscattering spectrometry (RBS), multiple crystal X-ray diffractometry (MCD) and transmission electron microscopy (TEM) is presented. In order to obtain a complete characterization of the analysed structure, three different quantities are measured independently: the epilayer thickness, the density of misfit dislocations which may appear at the interface, and the significant components of the strain tensor, mainly the tetragonal distortion, affecting the epilayer lattice. In this way the thermodynamic state and the mechanisms of plastic deformation of the structures can be fully investigated. In this contribution we present and discuss the experimental results concerning a set of InP/GaAs samples having different layer thicknesses ranging from 5 to 500 nm. The thickness of the samples has been determined by RBS. Measurements of in-plane strain and tetragonal distortion have been performed by MCD and RBS-channelling respectively, finally TEM has been used for determining the defects densities and distribution.     

High-intensity ultrasound and microwave, alone or combined, promote Pd/C-catalyzed aryl-aryl couplings

Pd-catalyzed homo- and cross-couplings of boronic acids and aryl halides were successfully carried out both in aqueous media under high-intensity ultrasound (US) and in DME under microwave (MW). Heterogeneous catalysis with Pd/C was employed, avoiding phosphine ligands and phase-transfer catalysts. In a trial series involving 15 different iodo- and bromoaryls and 7 boronic acids, both energy sources drastically reduced reaction times affording biaryls in acceptable to good yields. With palladium(II) acetate as catalyst, electron-deficient aryl chlorides also reacted, affording a few biaryls in acceptable yields. Ullmann-type zinc-mediated homocoupling of iodo- and bromoaryls in the presence of Pd/C under CO₂ atmosphere was achieved in aqueous media under US, though not under MW. Suzuki homo- and cross-couplings were also carried out in a new reactor developed in our laboratory, featuring combined US and MW irradiation, further improving a green synthetic method.