Gas chromatography retention data of environmentally relevant polybrominated compounds

Polybrominated organic compounds are ubiquitous throughout the environment. This generic term comprises several classes of brominated flame retardants (e.g., polybrominated diphenyl ethers, polybrominated biphenyls, hexabromocyclododecane, dibromopropyltribromophenyl ether, 1,2-bis(2,4,6-tribromophenoxy)ethane) as well as a range of marine halogenated natural products (HNPs). Here we present gas chromatography retention times and elution orders (on DB-5) of 122 polybrominated compounds that may be found in food and environmental samples. Organobromine compounds in fish samples determined with gas chromatography interfaced to electron-capture negative ion mass spectrometry (GC/ECNI-MS) are discussed. The environmental relevance and important mass spectrometric features of the compounds are described as well. Our database aims to support the closer inspection and identification of peaks in gas chromatograms and to initiate dedicated screening for less frequently studied organobromines in samples.     

Alteration of nC60 in the presence of environmentally relevant carboxylates

C(60) forms colloidally stable nanoscale particles (nC(60)) when mixed with water for extended periods. Past studies have shown that macromolecules such as natural organic matter (NOM) and proteins accelerate nC(60) formation and stabilize the resulting nanoparticles. To better elucidate the mechanisms underlying this behavior, nC(60) was produced via extended mixing in the presence of sodium citrate and other carboxylates. Carboxyl groups are a predominant functional group in many environmentally relevant macromolecules, thus studies examining carboxyl-C(60) interactions are merited. nC(60) produced in the presence of citrate (cit/nC(60)) and other carboxylates differs from nC(60) produced in water alone (aq/nC(60)), exhibiting enhanced negative surface charge, smaller particle size, and different spectroscopic characteristics. Importantly, the simultaneous detection of irregular nC(60) nanoparticles and small, regularly shaped nC(60) suggests that mixing-mediated "top-down" and carboxyl group-mediated "bottom-up" processes occur concurrently when nC(60) is produced in the presence of carboxylates and, by extension, in the presence of carboxylate-containing macromolecules. The "bottom-up" process is expected to involve molecular C(60) or small clusters of C(60) molecules as an important intermediate.     

Occurrence of environmentally relevant pharmaceuticals in Italian drinking water treatment plants

The occurrence and seasonal distribution of 14 pharmaceutical substances of different classes were investigated in two drinking water treatment plants (DWTPs) supplied by the two main Italian rivers, the Po and the Adige (Northern Italy). The therapeutic categories of the selected pharmaceuticals included anti-inflammatory drugs, β-blockers, lipid regulators, diuretics, anti-epileptics, antibiotics and a steroidal hormone. The named compounds were assessed in samples collected from the river water inlet and after each purification stage (sand filtration, ozone treatment, granular active carbon (GAC)). Six of the 14 selected pharmaceuticals were found in all analysed samples, with concentration levels ranging from 1?ng?l^?1 for atorvastatin to 69?ng?l^?1 for atenolol in the drinking water produced. The granular active carbon stage resulted the most efficient in eliminating the examined chemicals from the water (removal range: 12–95%, average: 68%), while the sand filtration stage resulted the least effective treatment (removal range: 4–37%, average: 13%). The observed differences between winter and summer conditions, in terms of residual concentrations and number of detected analytes, seemed to depend mainly on the quality of the river water supplies. To the best of our knowledge, these are the first reported data on the presence of pharmaceuticals in drinking water obtained from the water treatment of these two rivers.     

Base-catalyzed reactions of environmentally relevant N-chloro-piperidines. A quantum-chemical study

Electronic structure methods have been applied to calculate the gas and aqueous phase reaction energies for base-induced rearrangements of N-chloropiperidine, N-chloro-3-(hydroxymethyl)piperidine, and N-chloro-4-(4-fluorophenyl)-3-(hydroxymethyl)piperidine. These derivatives have been selected as representative models for studying the chemical fate of environmentally relevant chloramines. The performance of different computational methods (MP2, MP4, QCISD, B3LYP and B2PLYP) for calculating the thermochemistry of rearrangement reactions was assessed. The latter method produces energies similar to those obtained at G3B3(+) level, which themselves have been tested against experimental results. Experimental energy barriers and enthalpies for ring inversion, nitrogen inversion and dehydrochlorination reactions in N-chloropiperidine have been accurately reproduced when solvent effects have been included. It was also found that the combined use of continuum solvation models (e.g. CPCM) and explicit consideration of a single water molecule is sufficient to properly describe the water-assisted rearrangement of N-chlorinated compounds in basic media. In the case of N-chloro-4-(4-fluorophenyl)-3-(hydroxymethyl)piperidine, which represents the chlorinated metabolite of the antidepressant paroxetine, several different reactions (intramolecular addition, substitution, and elimination reactions) have been investigated. Transition state structures for these processes have been located together with minimum energy structures of conceivable products. Imine 4A is predicted to be the most stable reaction product, closely followed by imine 4B and oxazinane 8, while formation of isoxazolidine 7 is much less favourable. Calculated reaction barriers in aqueous solution are quite similar for all four processes, the lowest barrier being predicted for the formation of imine 4A.     

Particle size distributions of silver nanoparticles at environmentally relevant conditions

Silver nanoparticles (Ag NPs) are becoming increasingly popular as antimicrobial agents in consumer goods with consequent risk to environmental health from discharges. Environmentally relevant fate and transport investigations are limited but essential to gain understanding towards bioavailability and toxicology. In this study, monodisperse 15 nm citrate-stabilised Ag NPs were synthesised, characterised and then fractionated by flow field-flow fractionation (FlFFF) at environmentally relevant conditions (pH 5 or 8, presence of natural organic macromolecules (NOM) and presence of sodium or calcium). At low ionic strength, Ag NPs particle size increased as pH increased from 5 to 8. However, changing the ionic strength from 10⁻³ to 10⁻² M Na increased instability of the Ag NPs, and loss of peak at pH 5 but in the presence of humic substance (HS), a reduction in NP size was seen, most likely due to a reduction in the diffuse layer. The presence of Ca²⁺ ions, at the higher ionic strengths caused complete loss of the solution Ag NPs with or without HS, most likely due to aggregation. At the lower Ca²⁺ ionic strength the Ag NPs were still unstable, but again, in the presence of HS the NPs were largely dispersed. The presence of HS improved stability of Ag NPs under these conditions by forming a surface coating resulting in both steric and charge stabilisation. This work implies that Ag NPs could have long residence times in aquatic systems in the presence of HS potentially resulting in increased bioavailability.     

Enthalpimetric determination of fluoride

An injection calorimeter used for analytical and thermochemical purposes is described. Amounts of sodium fluoride between 6 and 8 mg are determined with an error of +/-0.04 mg. The calorimeter is also used in determining DeltaH for the precipitation of lead chloro-fluoride from water solutions with an ionic strength of 1M. DeltaH = 36.6 +/- 0.3 kJ mole . Quantitative analysis is made by flow microcalorimeter with amounts of sodium fluoride between 40 and 400mug and an error of +/-4 mug. An ion-exchange system for separation of fluoride from phosphate, sulphate, nitrate and chloride is also described.     

The determination of microgram quantities of fluoride : The determination 0f fluoride in waters and sewage effluent using the aluminium-haematoxylin complex

The application of the aluminium-haematoxylin reagent to the determination of fluoride in sea-water, river and potable waters, and sewage effluent is described. It has been shown that down to a level of about 0.1 p.p.m. the fluoride can be determined directly (i.e. without prior separation by distillation); there is some loss in accuracy for amounts of the order of 0.2–0.5 p.p.m. With sea-water, calibra tions should be carried out in a blank of artificial sea-water. The fluoride contents of a number of British rivers etc., are given.     

Fluorescent Zn chemosensors, functional in aqueous solution under environmentally relevant conditions

The synthesis and evaluation of two new ratiometric chemosensors for the quantification of potentially toxic free Zn²⁺ ions in aqueous solutions are described. Both sensors show high selectivity for Zn²⁺ over other cations, and are functional at environmentally relevant pH with detection limits of 0.05 μM for free Zn²⁺.     

Molecular fluorescence excitation-emission matrices relevant to tissue spectroscopy

In vivo and ex vivo studies of fluorescence from endogenous and exogenous molecules in tissues and cells are common for applications such as detection or characterization of early disease. A systematic determination of the excitation-emission matrices (EEM) of known and putative endogenous fluorophores and a number of exogenous fluorescent photodynamic therapy drugs has been performed in solution. The excitation wavelength range was 250-520 nm, with fluorescence emission spectra collected in the range 260-750 nm. In addition, EEM of intact normal and adenomatous human colon tissues are presented as an example of the relationship to the EEM of constituent fluorophores and illustrating the effects of tissue chromophore absorption. As a means to make this large quantity of spectral data generally available, an interactive database has been developed. This currently includes EEM and also absorption spectra of 35 different endogenous and exogenous fluorophores and chromophores and six photosensitizing agents. It is intended to maintain and extend this database in the public domain, accessible through the Photochemistry and Photobiology website (http://www.aspjournal. com/).     

Dihydropyrimidones based chloride ion chemosensor functional in aqueous solution under environmentally relevant conditions

Compounds 1 and 2 were synthesised using multi-component one-pot condensation reaction between 2-hydroxynaphthaldehyde, urea/thiourea and ethyl/methyl acetoacetate, catalysed with Zn(ClO₄)₂·6H₂O in methanol. Compounds 1 and 2 were purified and characterised using ¹H and ¹³C NMR, mass and CHN analyses. Organic nanoparticles (ONPs) were developed from compounds 1 and 2 using reprecipitation technique. Size and morphology of nano-aggregates N1 and N2 were analysed using DLS and transmission electron microscope techniques. Nano-aggregates of 1 and 2 were further subjected to chemosensory applications in aqueous medium. Efficient nano-aggregates of compound 1 have shown excellent detection limit of 0.04 nM for chloride in aqueous medium. None of the other anions tested caused any interference in the detection of chloride. However, nano-aggregates of compound N2 were not active for any particular ion in aqueous medium. The difference in the recognition properties can be due to the difference in the size and electronegativity of oxygen and sulfur moieties attached on 1 and 2, respectively. The sensor was used to determine the chloride content in tap water. Results were validated using existing methods and the performance of the N1 was found to be in a satisfactory error range.     

The determination of fluoride by titration with calcium chloride

A new method for the determination of fluoride ions is described. Precipitation is effected with an excess of standard calcium chloride and, after standing overnight, the unconsumed calcium ions are back-titrated with ethylenediamine tetra-acetic acid (EDTA) using Eriochrome Black T as indicator. Halides, sulphate, phosphate and arsenate do not interfere under the recommended conditions. The method is applicable over the range 5-65 mg of fluoride ion.     

Modelling of the reactivity and stability of carbon nanotubes under environmentally relevant conditions

The remarkable properties of carbon nanotubes have made them the preferred candidate for a number of exciting new technologies, and the intense focus of an enormous volume of scientific research. Much of this work is performed under highly idealized conditions, and less attention has typically been given to understanding what happens when carbon nanotubes are exposed to more realistic conditions, such as those typical in everyday devices. One of the most important aspects of this real world exposure will be the interaction of carbon nanotubes with our atmosphere. Adsorption of air will impact the stability of the carbon nanotubes, and may have undesirable consequences for the fundamental properties and the reliability of the device. Since this is a very challenging problem to address using experimental methods, it is often appropriate to begin by using theory and simulation. Presented here is a general analytical model for describing the thermodynamic stability of carbon nanotubes in the presence of gas adsorbates. This model is used to examine the stability of nanotubes in air, as a function of the relative humidity, but is equally applicable to any gaseous environments given suitable input parameters.     

Electrochemical determination of trace amounts of environmentally important dyes

A number of dyes exhibit genotoxic or ecotoxic properties leading to the need for sensitive and selective methods for their determination. Because of the easy reducibility of dyes, modern polarographic and voltammetric methods (differential pulse polarography on classical dropping mercury electrode, differential pulse voltammetry on hanging mercury drop electrode or adsorptive stripping voltammetry) are suitable for the determination of trace amounts of these substances in the general environment in the vicinity of production plants. The scope and limitations of these methods is reviewed and optimum conditions for recently developed methods are summarized. It is shown that the sensitivity of newly developed polarographic and voltammetric methods is sufficient even for the most demanding applications and their selectivity can be increased by their combination with preliminary separation using thin layer chromatography or liquid extraction.     

Electrochemical determination of trace amounts of environmentally important dyes

A number of dyes exhibit genotoxic or ecotoxic properties leading to the need for sensitive and selective methods for their determination. Because of the easy reducibility of dyes, modern polarographic and voltammetric methods (differential pulse polarography on classical dropping mercury electrode, differential pulse voltammetry on hanging mercury drop electrode or adsorptive stripping voltammetry) are suitable for the determination of trace amounts of these substances in the general environment in the vicinity of production plants. The scope and limitations of these methods is reviewed and optimum conditions for recently developed methods are summarized. It is shown that the sensitivity of newly developed polarographic and voltammetric methods is sufficient even for the most demanding applications and their selectivity can be increased by their combination with preliminary separation using thin layer chromatography or liquid extraction.     

Comparison of extraction techniques for isolation of steroid oestrogens in environmentally relevant concentrations from sediment

The comparison of four extraction techniques for isolation of five native and one labelled steroid oestrogens from sediment was described. The three conventional extraction techniques Soxhlet warm extraction (SWE), accelerated solvent extraction (ASE), microwave-assisted extraction (MAE) and a promising technique QuEChERS were tested for isolation of low environmentally relevant oestrogen concentrations using different extraction conditions. The least expensive and time-consuming method QuEChERS provided the best extraction recoveries (53–84%) from all techniques. MAE achieved the highest recovery from conventional techniques for less polar oestrogens using dichloromethane: acetone 3:1 mixture as an extraction solvent (50–71%), but for extraction of the whole group of oestrogens including more polar estriol acetone or methanol must be used. ASE provided higher extraction recoveries using dichloromethane at 60°C (53–74%) for less polar oestrogens. However, the repeatability of results was unsatisfactory and recoveries using other extraction conditions were lower than for MAE. The most time-consuming SWE achieved the worst extraction recoveries and for isolation of low oestrogen concentrations from sediments, it is completely unsuitable.     

An environmentally benign and practical synthesis of sugar orthoesters promoted by potassium fluoride

An extremely practical method for synthesis of sugar orthoesters has been developed without using any organic amines or heavy metals as additives. Various sugar orthoesters were prepared in good yields by the reaction of an acylated glycosyl bromide and an alcohol in the presence of potassium fluoride.     

The automatic determination of fluoride in sea water and other natural waters

A Technicon AutoAnalyzer has been used for the determination of 0–1.5 μg fluoride/ml in sea water and other natural waters. Photometric measurement is made on the blue complex formed by reaction with the chelate formed between lanthanum and alizarin fluorine blue, The method has a coefficient of variation of ca. 0.9% at a fluoride level of 1.5 μm/ml.     

Separation and determination of fluoride in plant samples

A simple and rapid separation method is described for the determination of fluoride in plant samples. Fluoride is separated by distillation in the presence of H(2)SO(4) and H(2)O(2) in a dry air steam. The variables that influence the distillation quantitation were optimized. The fluorides separated were subsequently determined by a spectrophotometric method of the La(III)-F(-)-alizarin complexone system. The precision of the procedure was significant, and the RSD was 3.7%. The accuracy of the method was statistically satisfactory, and the recovery was from 95.9 to 104.4%.