Spin-state dynamics of a photochromic iron(II) complex and its immobilization on oxide surfaces via phenol anchors

This work presents a detailed study of the photo-induced spin-state dynamics of the photochromic iron(II) complex 1, where the metal ion is in the field of a tripodal hexa-imine ligand with protolysable phenol groups. The nature of the complex’s ground state has been identified as a spin singlet by ¹H NMR and steady-state UV/vis spectroscopies, and its distorted octahedral structure was analyzed via crystal structure determination. Sub-picosecond and nanosecond time-resolved laser flash photolysis experiments identify the long-lived quintet state of 1 as the selective product of photoexcitation in the UV/vis spectral region. Thermal barriers of spin-state interconversion as a function of solvent and added base are derived from temperature-dependent rates of transient decay. Ground-state recovery is found to be significantly affected by the solvent and is strongly enhanced, in particular, by base-driven solvolysis of the ligand’s phenol groups. Partial spontaneous deprotonation of the phenolic hydroxyl groups of 1 seems to prevail on metal oxide surfaces, i.e. on alumina. Composite materials, like 1 at Al₂O₃, that retain the characteristic spectral features of the parent iron(II) complex can be readily obtained by wet impregnation of hydrous alumina with solutions of 1.     

Towards a comprehensive exploitation of agrofood residues: Olive tree – olive oil as example

A comprehensive use of residues from the agrofood industry requires development of a number of steps – discussed in this article taking as a model the olive tree – olive oil binomial – consisting of: (i) extraction, identification and quantitation of valuable products (with isolation of individual compounds, if required); (ii) assessment of beneficial effects (which could be made mainly through metabolomics); (iii) improvement of cultivation varieties (through cross-breeding or other agricultural resources); (iv) commercialization as nutraceuticals, food supplements, pharmaceuticals or even as antibacterial and antifoam agents in water treatment plants; (v) use of the final residues to produce compost, foodstuffs, biogas or heat (after checking the characteristics of these residues which can be very different from those of the original residue). This working scheme may be applied to any other system to break the traditional one cultivation–one commercial product scheme.     

Measurement of Phenols in Automobile Exhaust

Abstract

Methods were investigated to measure exhaust emission rates of individual low-molecular-weight phenols from gasoline and diesel vehicles driven on a chassis dynamometer using the FTP driving cycle. An extraction procedure to isolate the phenols from exhaust scrubs was evaluated. Separation of individual phenols was done by gas chromatography, with detection by a flame ionization detector. Phenol identifications were confirmed by mass spectroscopy. Results of a limited survey of gasoline and diesel vehicles are reported.     

Silica-Polyethyleneglycols/N 2 O 4 Complexes as Heterogeneous Nitrating and Nitrosating Agents

Silica-chloride was reacted with different quantities of H(OCH 2 CH 2 ) n OH (n = 2-4) to furnish silica-based linear polyethylene glycols and cyclic polyethylene glycolic ethers. The N 2 O 4 complex of silica-tetraethylene glycolic ether ( III ) was selected and used as a stable, cheap, and heterogeneous silica-based reagent for the selective mono- and dinitration of phenols and nitrosation of thiols.     

Melamine-(H_2SO_4)_3 and PVP-(H_2SO_4)_n as solid acids:Synthesis and application in the first mono-and di-nitration of bisphenol A and other phenols

Melamine and poly vinylpyrrolidone（PVP） reacted with neat sulfuric acid readily to form two new organic solid acids namely melamine-（H₂SO₄）₃ and PVP-（H₂SO₄）_n.These solid acids were used for the first nitration of bisphenol A as well as other phenols in the presence of NH₄NO₃.Mono- and di-nitro bisphenol A have been characterized with IR and ¹H NMR techniques.     

Gas chromatographic determination of some phenolic compounds in fuels and engine oil after simultaneous derivatization and microextraction

In this study, a simultaneous derivatization/air‐assisted liquid–liquid microextraction method has been developed for sample preparation of some phenolic compounds in fuels and engine oil. Analytes are transferred by back liquid–liquid extraction into NaOH solution and then are derivatized with butyl chloroformate and extracted simultaneously into carbon tetrachloride. The extracted derivatized analytes are analyzed using gas chromatography with flame ionization detection. The effect of extracting solvent type, derivatization agent and extraction solvent volumes, ionic strength of the aqueous solution, number of extraction cycles, etc., on the extraction efficiency is investigated. The calibration graphs are linear in the range of 3–10 000 μg/L. Enhancement factors, enrichment factors, and extraction recoveries are in the ranges of 497 to 1471, 571 to 991, and 60 to 109%, respectively. Detection limits are obtained in the range of 0.8 to 2.0 μg/L. Relative standard deviations for the extraction of each selected phenols are in the ranges of 2–4% for intraday (n = 6) and 3–6% (n = 5) for interday precisions for 200 μg/L. This technique is successfully applied for the extraction, preconcentration, and determination of the selected phenols in gasoline, kerosene, gas oil, and engine oil.     

Ultra-high-stability,pH-resistant sol–gel titania poly(tetrahydrofuran) coating for capillary microextraction on-line coupled to high-performance liquid chromatography

A sol–gel titania poly(tetrahydrofuran) (poly-THF) coating was developed for capillary microextraction hyphenated on-line with high-performance liquid chromatography (HPLC). Poly-THF was covalently bonded to the sol–gel titania network which, in turn, became chemically anchored to the inner surface of a 0.25 mm I.D. fused silica capillary. For sample preconcentration, a 38-cm segment of the sol–gel titania poly-THF coated capillary was installed on an HPLC injection port as a sampling loop. Aqueous samples containing a variety of analytes were passed through the capillary and, during this process, the analytes were extracted by the sol–gel titania poly-THF coating on the inner surface of the capillary. Using isocratic and gradient elution with acetonitrile/water mobile phases, the extracted analytes were desorbed into the on-line coupled HPLC column for separation and UV detection. The sol–gel titania poly-THF coating was especially efficient in extracting polar analytes, such as underivatized phenols, alcohols, amines, and aromatic carboxylic acids. In addition, this coating was capable of extracting moderately polar and nonpolar analytes, such as ketones and polycyclic aromatic hydrocarbons. The sol–gel titania poly-THF coated capillary was also able to extract polypeptides at pH values near their respective isoelectric points. Extraction of these compounds can be important for environmental and biomedical applications. The observed extraction behavior can be attributed to the polar and nonpolar moieties in the poly-THF structure. This coating was found to be stable under extremely low and high pH conditions—even after 18 h of exposure to 1 M HCl (pH ≈0.0) and 1 M NaOH (pH ≈14.0).     

Gas chromatographic retention indices of biologically and environmentally important organic compounds on capillary columns with low-polar stationary phases

This work presents linear temperature programmed retention indices on the columns with stationary phases of 5% phenylpolydimethyl silicone of 389 organic compounds, including extractive substances of plant tissues and environmentally important compounds. Certain factors which influence the values and reproducibility of retention indices during gas chromatographic analysis of multicomponent mixtures are discussed.     

An improved method for the simultaneous analysis of phenolic and steroidal estrogens in water and sediment

This paper describes an improved method for the extraction and analysis of seven endocrine disrupting chemicals with wide-ranging polarities from water and sediments using gas chromatography-tandem mass spectrometry (GC-MS/MS). The analytes were 4-tert-octylphenol, 4-nonylphenol, bisphenol A, estrone, 17β-estradiol, 17α-ethynylestradiol and 16α-hydroxyestrone. The optimised GC-MS/MS method produces increased selectivity and sensitivity compared to GC-MS, with limit of detection ranging from 0.01 to 0.49 ng L⁻¹ in water and from 0.05 to 0.14 ng g⁻¹ in sediment. Extraction from aqueous samples was performed by solid-phase extraction (SPE) and from sediment samples by microwave-assisted extraction (MAE). The improved method for the clean-up of sediment extracts carried out by SPE enhanced EDC recovery (86-102%) while reducing matrix interference and sample drying time. Derivatisation of final sample extracts was achieved using N,O-bis(trimethylsilyl)trifluoroacetamide and pyridine, and their stability was enhanced by reconstituting the derivatised extracts with hexane. The method was validated by spiking experiments which showed good recovery and reproducibility. The method was applied to samples taken from the Medway estuary in Kent, UK, where non-conservative behaviour of EDCs was demonstrated.     

Sensitive determination of phenols in environmental water samples with SPE packed with bamboo carbon prior to HPLC

Bamboo carbon, an inexpensive, readily available material, has attracted great attention in recent years because of adsorptive properties. In this paper, the potential of bamboo carbon as a SPE adsorbent for the determination of phenols, was investigated. Phenols are important environmental contaminants that may adversely affect human health. Parameters influencing extraction efficiency, including type of eluent, eluent volume, amount of adsorbent, as well as sample pH, volume, and flow rate were investigated and optimized. The optimized results exhibited excellent linear relationships between peak area and phenol concentrations over the range of 2.0–100 ng/mL, with precision between 2.2–7.2%. The LODs were 0.06–0.4 ng/mL for the eight phenols tested. The proposed method has been successfully applied to the analysis of several real‐world environmental water samples. These results indicate that bamboo carbon may be used as a novel SPE adsorbent for the concentration and determination of phenols in real environmental water samples.