Uncertainty evaluation for the quantification of low masses of benzo[a]pyrene: Comparison between the Law of Propagation of Uncertainty and the Monte Carlo method

A proper evaluation of the uncertainty associated to the quantification of micropollutants in the environment, like Polycyclic Aromatic Hydrocarbons (PAHs), is crucial for the reliability of the measurement results. The present work describes a comparison between the uncertainty evaluation carried out according to the GUM uncertainty framework and the Monte Carlo (MC) method. This comparison was carried out starting from real data sets obtained from the quantification of benzo[a]pyrene (BaP), spiked on filters commonly used for airborne particulate matter sampling. BaP was chosen as target analyte as it is listed in the current European legislation as marker of the carcinogenic risk for the whole class of PAHs.     

Deposition and characterization of a CoHCF nanorod array in a templated ormosil film on an electrode and application to electrocatalysis

Cobalt hexacyanoferrate (CoHCF) was electrodeposited into an organically modified silica (ormosil) film with a nanoarray of parallel, cylindrical channels, which were obtained using 20-nm poly(styrene sulfonate), PSS, beads as a templating agent. The PSS was bound to the electrode surface with 3-aminopropyltriethoxysilane, APTES. Methoxytrimethylsilane was the ormosil precursor. Electrochemically assisted processing at a positive potential where the hydrogen ion catalyst was generated was used to deposit the ormosil film. Subsequently, the PSS and APTES were removed to provide the pores. The CoHCF was deposited in the 20-nm channels by cyclic voltammetry of a freshly prepared K₃Fe(CN)₆, CoCl₂ mixture with 1.0 mol dm^?3 KCl as the supporting electrolyte. Limiting the number of electrodeposition cycles to 10–20 resulted in CoHCF nanorods in the pores, whereas with 50 cycles bulk-form CoHCF spilled over the outer ormosil surface. Electrocatalytic oxidation of cysteine was successfully performed on these nanorod arrays, which showed greater catalytic activity than bulk-form CoHCF.     

Reversible gas uptake by a nonporous crystalline solid involving multiple changes in covalent bonding

Hydrogen chloride gas (HCl) is absorbed (and reversibly released) by a nonporous crystalline solid, [CuCl2(3-Clpy)2] (3-Clpy = 3-chloropyridine), under ambient conditions leading to conversion from the blue coordination compound to the yellow salt (3-ClpyH)2[CuCl4]. These reactions require substantial motions within the crystalline solid including a change in the copper coordination environment from square planar to tetrahedral. This process also involves cleavage of the covalent bond of the gaseous molecules (H-Cl) and of coordination bonds of the molecular solid compound (Cu-N) and formation of N-H and Cu-Cl bonds. These reactions are not a single-crystal-to-single-crystal transformation; thus, the crystal structure determinations have been performed using X-ray powder diffraction. Importantly, we demonstrate that these reactions proceed in the absence of solvent or water vapor, ruling out the possibility of a water-assisted (microscopic recrystallization) mechanism, which is remarkable given all the structural changes needed for the process to take place. Gas-phase FTIR spectroscopy has permitted us to establish that this process is actually a solid-gas equilibrium, and time-resolved X-ray powder diffraction (both in situ and ex situ) has been used for the study of possible intermediates as well as the kinetics of the reaction.     

Homo- and hetero-dinuclear anion complexes

The tripodal system 4, in which urea fragments are appended to the three terminal amine nitrogen atoms of a tris(2-aminoethyl)amine (tren) subunit, includes a Cu(II) ion and two anions X-, according to a cascade mechanism through three well defined stepwise equilibria in a DMSO solution. The first anion X- (halide, N3-, NCS-, NO2-, H2PO4-) seeks the Cu(II) centre coordinated by the tren moiety; the second anion X- interacts with the trisurea cavity, but this occurs only if the stronger H-bond acceptors, such as N3- and H2PO4-, are used. Binding of the second X- ion is favoured by the preorganising effect exerted by the metal and disfavoured by the steric and electrostatic repulsions between the anions. Under the appropriate conditions, heterodinuclear complexes of formula [Cu(II)(4)(Cl)(H2PO4)] can be obtained in solution, in which Cl- is bound to the metal centre and H2PO4- interacts with the trisurea compartment.     

2-substituted benzofuran fragment ion formation in the electron ionization mass spectra of 6-alkyl- and 6-aryldibenzo(d,f)(1,3)dioxepine derivatives. 1. Spirocyclization of the molecular ions in the gas phase

The formation of 2-substituted benzo[b]furan ions in the electron ionization (EI) mass spectra of a series of 6-alkyl- and 6-aryldibenzo(d,f)(1,3)dioxepines has been studied by means of exact mass measurements and multiple-stage mass spectrometry conditions using an ion trap mass spectrometer. The proposed mechanism of formation of benzo[b]furan ions requires the formation of a spirocyclic cyclohexadienone system, which undergoes elimination of a cyclopentadienone molecule. A parallel with the chemical conversion of arylmethyl-substituted dibenzo(d,f)(1,3)dioxepines into an analogous spirocyclic system was also underlined.     

Synthesis of beta‐proline like derivatives and their evaluation as sodium channel blockers

A simple and convenient procedure for the preparation of beta‐proline like derivatives in their racemic and optically active forms has been reported. The compounds have been screened for their potential activity as sodium channel blockers.     

DFT evidence for a stepwise mechanism in the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals

Hybrid DFT calculations of the potential energy surface (PES) relative to the O-neophyl rearrangement of a series of ring-substituted 1,1-diarylalkoxyl radicals have been carried out at the UB3LYP/6-31G(d) level of theory. On the basis of the computational data, the rearrangement can be described as a consecutive reaction of the type a <--/--> b --> c (see above graphic), and the steady-state approximation could be applied in all cases to the intermediate b. The first-order rearrangement rate constants [kobs = k1k2/(k-1 + k2)] were thus obtained from the computed activation free-energies and were compared with the experimental rate constants measured previously in MeCN solution by laser flash photolysis. An excellent agreement is observed along the two series, which strongly supports the hypothesis that the O-neophyl rearrangement of 1,1-diarylalkoxyl radicals proceeds through the formation of the reactive 1-oxaspiro [2,5]octadienyl radical intermediate. This is in contrast to previous hypotheses that involve either a long-lived intermediate or the absence of this intermediate along the reaction path. The calculated rearrangement free-energies decrease upon going from the methoxy-substituted radical (Delta G degrees = -16.4 kcal x mol-1) to the nitro-substituted one (Delta G degrees = -21.8 kcal x mol-1), which follows a trend that is similar to the one observed for the CAr-O bond dissociation enthalpies (BDEs) of ring-substituted anisoles. This evidence indicates that in the O-neophyl rearrangement the effect of ring substituents on the strength of the newly formed CAr-O bond plays an important role.     

Hydrogenation of Quinoline by Rhodium Catalysts Modified with the Tripodal Polyphosphine Ligand MeC(CH2PPh2)3

As part of our modelling studies of the hydrodenitrogenation of N‐heterocycles contained in raw oil materials, we investigated the selective hydrogenation of quinoline to 1,2,3,4‐tetrahydroquinoline by rhodium catalysts modified with the tripodal polyphosphane ligand MeC(CH₂PPh₂)₃. Experiments in standard autoclaves and in high‐pressure sapphire NMR tubes, kinetic and isotope labelling studies, and independent reactions with isolated compounds have contributed to the elucidation of the catalytic mechanism as well as identification of the electronic requisites of the metal catalyst for selective and efficient hydrogenation.     

Kabuli and Apulian black Chickpea Milling By-Products as Innovative Ingredients to Provide High Levels of Dietary Fibre and Bioactive Compounds in Gluten-Free Fresh Pasta

Gluten-free (GF) products, including pasta, are often characterised by nutritional deficiencies, such as scarce dietary fibre and excess of calories. Chickpea flour is increasingly being used by the food industries. Hulls, rich in dietary fibre and bioactive compounds, are discarded after milling. The aim of this work was to evaluate the quality features of short-cut GF fresh pasta added of hull (8% w/w) derived from kabuli (KH) or Apulian black (ABH) chickpeas, in comparison with control GF pasta prepared without hull. The enriched pasta, which could be labelled as “high fibre”, was characterised by a higher level of bioactive compounds and antioxidant activity than the control. ABH-enriched pasta showed the highest anthocyanins (33.37 ± 1.20 and 20.59 ± 0.11 mg/kg of cyanidin-3-O-glucoside on dry matter in raw and cooked pasta, respectively). Hull addition increased colour intensity and structural quality of GF pasta: ABH-enriched pasta had the lowest cooking loss and the highest water absorption capacity; KH-enriched pasta showed the highest firmness. No significant differences in sensory liking were found among the samples, except for “aftertaste”. Chickpea hull can be used as an innovative ingredient to produce potentially functional GF pasta, meeting the dietary needs of consumers without affecting quality.     

Solid‐phase extraction and HPLC determination of fluoroquinolones in surface waters

An investigation on filtration procedures and SPE sorbents used for the determination of traces of the most common veterinary fluoroquinolones (FQs), marbofloxacin (MAR) and enrofloxacin (ENR) used as antibacterial agents in cattle and swine farms in the province of Pavia (Italy), was performed in natural waters. The filter composition and the sorbent used in the SPE strongly influence the correct recovery, both in terms of total and dissolved FQs concentration. An accurate comparison among different filters and SPE sorbents showed that a full determination of analytes was possible on nylon filters followed by anionic (WAX) and hydrophilic–lipophilic balance (HLB) resins as SPE. Quantitative analysis was done by chromatography with fluorescence detection (HPLC‐FD). Fluoroquinolones recovery was between 90 and 116% with RSD not greater than 10% (sample volume 250 mL). The developed method allowed to determine both dissolved and NOM‐absorbed fractions of FQs, therefore a full determination of the analytes was possible. Limits of detection (LOD) and quantification (LOQ) were, respectively, 0.7 and 2.2 ng/L for ENR and 2 and 6 ng/L for MAR. The kinetics of degradation under solar light was explored.