A miniaturized active sampler for the assessment of personal exposure to nitrogen dioxide

A personalized, miniaturized air sampling system was evaluated to estimate the daily exposure of pediatric asthmatics to nitrogen dioxide (NO₂). The lightweight device (170 g) uses a sampling pump connected to a solid sorbent tube containing triethanolamine (TEA)-impregnated molecular sieve. The pump is powered by a 9 V battery and samples air over a 24 h period at a collection rate of 0.100 L/min. After exposure, the solid sorbent is removed from the tubes for spectrophotometric analysis (Griess Assay). The lower detection limit of the overall method for NO₂ is 11 μg/m³. The linearity, precision and accuracy of the sampler was evaluated. Different NO₂ concentrations generated in the laboratory (range: 50 to 340 μg/m³) were simultaneously measured by the TEA tube samplers and colocated continuous chemiluminescent NO_x analyzers (reference method). The coefficient of determination for the laboratory test derived from ordinary linear regression (OLR) was r ²=0.99 (y _OLR=0.94x−4.58) and the precision 3.6%. Further, ambient NO₂ concentrations in the field (range: 10–120 μg/m³) were verified with continuous chemiluminescent monitors next to the active samplers. Reweighted least squares analysis (RLS) based on the least median squares procedure (LMS) resulted in a correlation of r ²=0.68 for a field comparison in Riverside, CA (y _RLS=1.01x−0.94) and r ²=0.92 in Los Angeles, CA (y _RLS=1.31x−7.12). The precision of the TEA tube devices was 7.4% (at 20–60 μg/m³ NO₂) under outdoor conditions. Data show that the performance of this small active sampling system was satisfactory for measuring environmental concentrations of NO₂ under laboratory and field conditions. It is useful for personal monitoring of NO₂ in environmental epidemiology studies where daily measurements are desired.     

The crystal structure of triphenylallyltin

The crystal structure of (C₆H₅)₃SnCH₂CHCH₂ has been determined. The asymmetric unit consists of two molecules of triphenylallyltin having virtually the same conformation. Their geometrical parameters exclude p_π-d_π bonding between the metal and the allyl double bond, and seem to be in a better agreement with a σ-π conjugation effect.     

Divergent sequential reactions of β-(2-aminophenyl)-α,β-ynones with nitrogen nucleophiles

β-(2-Aminophenyl)-α,β-ynones readily react with nitrogen nucleophiles to give three major types of products, depending on reaction conditions and variation in the nucleophiles. The reaction may lead to simple 1,2-nucleophilic adducts or, at higher temperatures, to a divergent sequential cyclisation giving rise to 2-aryl-4-aminoquinolines by reaction with amines, or to substituted 2-aryl or 2-alkyl-4-alkylidene quinazolines by reaction with amidines. The latter could also be synthesised by reaction of β-(2-aminophenyl)-α,β-ynones with iminochlorides.     

Single-Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2–3/2 Spin Admixture

A mononuclear iron(III) porphyrin compound exhibiting unexpectedly slow magnetic relaxation, which is a characteristic of single-ion magnet behaviour, is reported. This behaviour originates from the close proximity (≈550 cm⁻¹) of the intermediate-spin S=3/2 excited states to the high-spin S=5/2 ground state. More quantitatively, although the ground state is mostly S=5/2, a spin-admixture model evidences a sizable contribution (≈15 %) of S=3/2 to the ground state, which as a consequence experiences large and positive axial anisotropy (D=+19.2 cm⁻¹). Frequency-domain EPR spectroscopy allowed the m_S= |±1/2⟩→|±3/2⟩ transitions to be directly accessed, and thus the very large zero-field splitting in this 3d⁵ system to be unambiguously measured. Other experimental results including magnetisation, Mössbauer, and field-domain EPR studies are consistent with this model, which is also supported by theoretical calculations.     

Self-assembly of water cluster in iron(III) oxalate-bridged complexes

The synthesis and crystal structural characterization of the compound of formula {[Fe^II(phen)₃]₂[Fe₂^IIIox₅]}·11H₂O (1) has been reported. The most interesting feature of the solid state structure of 1 consists in the occurrence of decanuclear water clusters made up of self-assembled cyclic hexameric water clusters with a quasi-planar conformation, unclosed trinuclear clusters and individual water molecules. The decanuclear water clusters are connected to the host lattices via an extensive net of strong hydrogen bonds that finally lead to an extended 3D supramolecular organization, wherein hexameric water clusters interconnected with dodecameric hybrid water–O_oxalate clusters can be identified. The comparison of this supramolecular architecture with that found in the already known compound of formula [Fe(bpm)₃]₂[Fe₂(ox)₅]·8H₂O (2) allows some preliminary observations on the design and control of water cluster nuclearity and conformation.     

Electrochemical Oxidation of the Antiretroviral Drug Nelfinavir on Modified Screen‐printed Electrodes

This paper describes the voltammetric study of the electrochemical oxidation of the antiretroviral drug Nelfinavir using a screen‐printed sensor modified with carbon nanotubes. The performance of the sensor in the determination of the drug was characterized in terms of precision (RSD 5.05 %, n=5) and capability of detection (10.99±0.87 μM for α=β=0.05, n=5) under optimized voltammetric conditions of pH, accumulation time and potential, in the calibration range from 10 to 150 μM of NFV. In order to check the viability of the device, the determination of the analyte in pharmaceutical and biological samples was carried out and its performance was also validated comparing it with HPLC.     

CLUSKEXT: CLUstering model for SKew-symmetric data including EXTernal information

Advances in Data Analysis and Classification - A CLUstering model for SKew-symmetric data including EXTernal information (CLUSKEXT) is proposed, which relies on the decomposition of a...