Feasibility of employing permanent chemical modifiers for the determination of cadmium in coal using slurry sampling electrothermal atomic absorption spectrometry

Iridium and ruthenium, alone and in combination with tungsten, thermally deposited on the platform of a transversely heated graphite tube, were investigated for their suitability as permanent chemical modifiers for the determination of cadmium in coal slurries by electrothermal atomic absorption spectrometry (ET AAS). The conventional mixed palladium and magnesium nitrates (Pd–Mg) modifiers, added in solution, were also investigated for comparison. The latter one showed the best performance for aqueous solutions, and the mixed W–Ir and W–Ru permanent modifiers had the lowest stabilizing power. All of the investigated modifiers lost some of their stabilizing power when coal slurries were investigated. The Pd–Mg modifier, pure Ir and Ru, and a mixture of 300 μg W + 200 μg Ir could stabilize Cd at least to a pyrolysis temperature of 600 °C, whereas all the other combinations already failed at temperatures above 500–550 °C. Additional investigations of the supernatant liquid of the slurries supported the assumption that the high acid concentration of the slurries and/or a concomitant leaching out of the coal might be responsible for the reduced stabilizing power of the modifiers. The maximum applicable pyrolysis temperature of 600 °C was not sufficient to reduce the background absorption to a manageable level in the majority of the coal samples. High-resolution continuum source ET AAS revealed that the continuous background absorption was exceeding values of A = 2, and was overlapping with the analyte signal. Although the latter technique could correct for this background absorption, some analyte was apparently lost with the rapidly vaporizing matrix so that the method could not be considered to be rugged. A characteristic mass of 1.0 pg and a detection limit of 0.6 ng g^− 1 could be obtained under these conditions.     

Efficient synthesis of an enantiopure beta-lactam as an advanced precursor of thrombin and tryptase inhibitors

A new and efficient synthesis of a beta-lactam that is an advanced precursor of inhibitors of thrombin and tryptase is reported. The reaction sequence is based on the use of an inexpensive enantiomerically pure starting material and is designed to allow access to both enantiomers of the target molecules by epimerization of a side-product obtained along the synthesis. An improved procedure for the epimerization step that takes advantage of the use of a polymer-supported and recyclable phase-transfer catalyst is described.     

Diaryl-2-pyrrolidinemethanols catalyzed enantioselective epoxidation of α,β-enones: new insight into the effect of structural modification of the catalyst on reaction efficiency

Catalytic enantioselective epoxidation of α,β-unsaturated ketones promoted by diaryl-2-pyrrolidinemethanols and tert-butyl hydroperoxide (TBHP) is described. Investigation on structural modifications of the diaryl-2-pyrrolidinemethanols showed that fine tuning of the stereoelectronics of the substituents on the aryl moiety is important to achieve high efficiency. By employing a structurally optimized organocatalyst, significantly reduced loading (10 mol %) can be used to produce the epoxides in high yield and up to 90% ee at room temperature.     

Development of an integrated capillary electrophoresis/sensor for L-ascorbic acid detection

A CE/biosensor for measuring ascorbic acid was developed by coupling a polyaniline optical sensor and capillary electrophoresis (CE). The capillary column was partially modified with a thin film of polyaniline redox sensitive material. Ascorbic acid was detected by monitoring the changes in optical absorbance occurring to the polyaniline film upon the reduction reaction. The sensor response (change in optical absorbance at 650 nm) is proportional to the concentration of ascorbic acid over a range of 2.5-250 mg/L and the response range has shown a clear dependence on the characteristics of the polymerized film. High specificity and sensitivity of the present method, low sample consumption, short times of response (ca. 2 min) and the reproducibility of the results demonstrate that the CE/polyaniline-sensor could be further employed in the study of the relation between the content of L-ascorbic acid in body fluids and clinical parameters, e.g., cell ageing.     

Cooking activities during the Middle Ages: organic residues in ceramic vessels from the Sant'Antimo Church (Piombino-Central Italy)

A combined gas chromatography-electron ionization (GC-EI), atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and MS/MS approach has been used for characterizing organic residues of ceramic vessels of different forms and dimensions recovered from a vault of the apse of the 13th century church of Sant'Antimo in Piombino (Central Italy). The artifacts studied in this investigation are pots, jugs, colanders and pans probably used for cooking meals or as food containers. GC-MS has shown the presence of different fatty acids and other nonpolar markers, while APCI ionization proved to be particularly useful in the detection of diterpenoids and diacylglycerols. The data show that some organic markers may be of animal origin, while others are typical constituents or biodegradation products of vegetables. This allows one to propose the main use of these articles as vessels for cooking meat and maybe vegetable broths and soups. As there is no strict correlation between organic markers and shape, form and dimension of the ceramic vessel, it appears that the different objects probably served the same function. Chemical characterization of the organic residues of ceramic vessels, together with all the other archaeological data, contributes to a better understanding of their uses and the customs of people in the Middle Ages in Central Italy.     

The hydrolysis mechanism of the anticancer ruthenium drugs NAMI-A and ICR investigated by DFT-PCM calculations

(ImH)[trans-RuCl(4)(DMSO-S)(Im)], (Im = imidazole, DMSO-S = S-bonded dimethylsulfoxide), NAMI-A, is the first anticancer ruthenium compound that successfully completed Phase I clinical trials. NAMI-A shows a remarkable activity against lung metastases of solid tumors, but is not effective in the reduction of primary cancer. The structurally similar (ImH)[trans-RuCl(4)(Im)(2)], ICR (or KP418), and its indazole analog (KP1019) are promising candidate drugs in the treatment of colorectal cancers, but have no antimetastatic activity. Despite the pharmacological relevance of these compounds, no rationale has been furnished to explain their markedly different activity. While the nature of the chemical species responsible for their antimetastatic/anticancer activity has not been determined, it has been suggested that the difference between reduction potentials of NAMI-A and ICR may be the key to the different biological responses they induce. In this work, Density Functional Theory calculations were performed to investigate the hydrolysis of NAMI-A and ICR in both Ru(III) and Ru(II) oxidation states, up to the third aquation. In line with experimental findings, our calculations provide a picture of the hydrolysis of NAMI-A and ICR mainly as a stepwise loss of chloride ligands. While dissociation of Im is unlikely under neutral conditions, that of DMSO becomes competitive with the loss of chloride ions as the hydrolysis proceeds. Redox properties of NAMI-A and ICR and of their most relevant hydrolytic intermediates were also studied in order to monitor the effects of biological reductants on the mechanism of action. Our findings may contribute to the identification of the active compounds that interact with biological targets, and to explain the different biological activity of NAMI-A and ICR.     

Smoothness of Hessenberg and Bidiagonal Forms

Our purpose in this work is to explore smoothness properties of transformations of a matrix valued function A to Hessenberg and bidiagonal form. The interplay with the rank of associated Krylov functions is exploited to clarify what one should expect for smooth functions A satisfying generic properties. This work was supported in part under INDAM-GNCS and MIUR Rome-Italy.     

Ocimum campechianum Mill. from Amazonian Ecuador: Chemical Composition and Biological Activities of Extracts and Their Main Constituents (Eugenol and Rosmarinic Acid)

The essential oil (EO), the methanolic (MeOH), and the 70% ethanolic (70% EtOH) extracts obtained from the aerial parts of Ocimum campechianum Mill. (Ecuador) were chemically characterized through gas-chromatography coupled to mass spectrometry detector (GC-MS), high-performance liquid chromatography coupled to diode array-mass spectrometry detectors (HPLC-DAD-MS) and studied for their in vitro biological activity. The radical scavenger activity, performed by spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, highlighted significant IC₅₀ values for the EO, extracts and their main constituents (eugenol and rosmarinic acid). EO (and eugenol) showed noteworthy activity against Pseudomonas syringae pv. syringae and a moderate effect against clinical Candida strains, with possible synergism in association to fluconazole against the latter microorganisms. The extracts and pure molecules exhibited weak cytotoxic activity against the HaCat cell line and no mutagenicity against Salmonella typhimurium TA98 and TA100 strains, giving indication of safety. Instead, EO showed a weak activity against adenocarcinomic human alveolar basal epithelial cells (A549). The above-mentioned evidence leads us to suggest a potential use of the crude drug, extracts, and EO in cosmetic formulation and food supplements as antioxidant agents. In addition, EO may also have a possible application in plant protection and anti-Candida formulations.     

QSAR Models for Human Carcinogenicity: An Assessment Based on Oral and Inhalation Slope Factors

Carcinogenicity is a crucial endpoint for the safety assessment of chemicals and products. During the last few decades, the development of quantitative structure–activity relationship ((Q)SAR) models has gained importance for regulatory use, in combination with in vitro testing or expert-based reasoning. Several classification models can now predict both human and rat carcinogenicity, but there are few models to quantitatively assess carcinogenicity in humans. To our knowledge, slope factor (SF), a parameter describing carcinogenicity potential used especially for human risk assessment of contaminated sites, has never been modeled for both inhalation and oral exposures. In this study, we developed classification and regression models for inhalation and oral SFs using data from the Risk Assessment Information System (RAIS) and different machine learning approaches. The models performed well in classification, with accuracies for the external set of 0.76 and 0.74 for oral and inhalation exposure, respectively, and r² values of 0.57 and 0.65 in the regression models for oral and inhalation SFs in external validation. These models might therefore support regulators in (de)prioritizing substances for regulatory action and in weighing evidence in the context of chemical safety assessments. Moreover, these models are implemented on the VEGA platform and are now freely downloadable online.