Membrane-assisted solvent extraction coupled to large volume injection–gas chromatography–mass spectrometry for the determination of a variety of endocrine disrupting compounds in environmental water samples

Membrane-assisted solvent extraction coupled to large volume injection in a programmable temperature vaporisation injector using gas chromatography–mass spectrometry analysis was optimised for the simultaneous determination of a variety of endocrine disrupting compounds in environmental water samples (estuarine, river and wastewater). Among the analytes studied, certain hormones, alkylphenols and bisphenol A were included. The nature of membranes, extraction solvent, extraction temperature, solvent volume, extraction time, ionic strength and methanol addition were evaluated during the optimisation of the extraction. Matrix effects during the extraction step were studied in different environmental water samples: estuarine water, river water and wastewater (influent and effluent). Strong matrix effects were observed for most of the compounds in influent and effluent samples. Different approaches were studied in order to correct or minimise matrix effects, which included the use of deuterated analogues, matrix-matched calibration, standard addition calibration, dilution of the sample and clean-up of the extract using solid-phase extraction (SPE). The use of deuterated analogues corrected satisfactorily matrix effect for estuarine and effluent samples for most of the compounds. However, in the case of influent samples, standard addition calibration and dilution of the sample were the best approaches. The SPE clean-up provided similar recoveries to those obtained after correction with the corresponding deuterated analogue but better chromatographic signal was obtained in the case of effluent samples. Method detection limits in the 5–54 ng L⁻¹ range and precision, calculated as relative standard deviation, in the 2–25% range were obtained.     

Neural networks for prediction of ultrafiltration transmembrane pressure – application to drinking water production

Modelling of ultrafiltration plants for drinking water production appears as a necessary step before plants control and supervisory. It first requires a better knowledge about membrane fouling by natural waters. The phenomena involved are very complex, because of the nature of the fluid concerned: water. Thus up to now phenomenological model cannot be applied for resource waters. Because of their properties, new modelling tools called neural networks seem to be a promising way to model complex phenomena and therefore to be applied to water treatment. In the present study a neural network is used to model the time evolution of transmembrane pressures for ultrafiltration membranes applied to drinking water production. Different network structures and architectures have been elaborated and evaluated with the aim of computing the pressure at the end of a filtration cycle and after the next backwash. For some of these networks a very good accuracy is obtained for both pressures predictions. The inlets are permeate flow rate, turbidity during the cycle and pressure measurements at the cycle start and at the end of the previous cycle. These networks are able to model the effect of both reversible and irreversible fouling on pressures even if no inlet parameter concerning organic matters is considered.     

Convenient and rapid synthesis of α-aminonitriles starting directly from nitro compounds in water

A distinct approach for the synthesis of α-aminonitriles has been discovered by three-component reaction of nitroarenes, aldehydes, and TMSCN using indium in dilute aqueous HCl at room temperature. The products were formed in high yields (86-96%) within a short period of time (5-20 min). This one-pot conversion consists of the following steps: (i) reduction of nitro compounds to amines, (ii) formation of imines from amines and aldehydes and (iii) addition of cyanide anion to the imines.     

Direct synthesis of carbonyl compounds from THP ethers with IBX in the presence of β-cyclodextrin in water

Water, an environmentally friendly reaction medium, has been utilized for the oxidative deprotection of tetrahydropyranyl ethers 1 with IBX at room temperature in the presence of β-cyclodextrin to give the corresponding carbonyl compounds 2.     

Encapsulation of β-cyclodextrin by in situ polymerization with vinyl chloride leading to suppressing the migration of endocrine disrupting phthalate plasticizer

We performed the encapsulation of β-cyclodextrin (β-CD) in PVC by in situ polymerization with vinyl chloride monomer (VCM), and investigated the effect of CD encapsulation on the suppression of dioctyl phthalate (DOP) migration suspected as endocrine disruptor. β-CD was partially modified with 3-(methacryloxy)propyl trimethoxysilane and modified β-CD (MCD) was then encapsulated in PVC through suspension polymerization via radical reaction between double bonds MCD and VCM. Resulting MCD-encapsulated PVC (MCD_x-PVC) exhibited the similar morphology and characteristics to commercial PVC. For MCD_x-PVCs plasticized with DOP, they showed the considerably suppressed DOP migration as well as the similar optical and mechanical properties to conventionally plasticized PVC. In particular, the plasticized MCD_x-PVCs exhibited the superior suppression of DOP migration compared to the plasticized PVC where MCD and DOP were introduced by conventional melt mixing. Therefore, the encapsulation of MCD in PVC is thought to be an effective approach to producing the ecological PVC material.     

Are luminescent bacteria suitable for online detection and monitoring of toxic compounds in drinking water and its sources?

Biosensors based on luminescent bacteria may be valuable tools to monitor the chemical quality and safety of surface and drinking water. In this review, an overview is presented of the recombinant strains available that harbour the bacterial luciferase genes luxCDABE, and which may be used in an online biosensor for water quality monitoring. Many bacterial strains have been described for the detection of a broad range of toxicity parameters, including DNA damage, protein damage, membrane damage, oxidative stress, organic pollutants, and heavy metals. Most lux strains have sensitivities with detection limits ranging from milligrams per litre to micrograms per litre, usually with higher sensitivities in compound-specific strains. Although the sensitivity of lux strains can be enhanced by various molecular manipulations, most reported detection thresholds are still too high to detect levels of individual contaminants as they occur nowadays in European drinking waters. However, lux strains sensing specific toxic effects have the advantage of being able to respond to mixtures of contaminants inducing the same effect, and thus could be used as a sensor for the sum effect, including the effect of compounds that are as yet not identified by chemical analysis. An evaluation of the suitability of lux strains for monitoring surface and drinking water is therefore provided.     

Determination of short-chain carbonyl compounds in drinking water matrices by bar adsorptive micro-extraction (BAμE) with in situ derivatization

In this contribution, bar adsorptive micro-extraction using polystyrene-divinylbenzene sorbent phase and in situ derivatization with pentafluorophenyl hydrazine, followed by liquid desorption and high-performance liquid chromatography-diode array detection (BAμE(PS-DVB)(PFPH in situ)-LD/HPLC-DAD), was developed for the determination of six short-chain carbonyl compounds (formaldehyde, acetaldehyde, propanal, acetone, butanone, and 2-hexenal) in drinking water matrices. PFPH presented very good specificity as an in situ derivatization agent for short-chain ketones and aldehydes in aqueous media, allowing the formation of adducts with remarkable sensitivity, selectivity and the absence of photodegradation. Assays performed on 30-mL water samples spiked at the 25.0 μg L(-1) levels, under optimized experimental conditions, yielded recoveries ranging from 47.4 ± 3.8% to 85.2 ± 3.8%, in which the PS-DVB proved to be a convenient sorbent phase. The analytical performance showed good accuracy, suitable precision (RSD < 13.0%), detection limits in between 47 and 132 ng L(-1) and remarkable linear dynamic ranges (r(2) > 0.9907) from 1.0 to 80.0 μg L(-1). By using the standard addition methodology, the application of the present method to drinking water samples treated with different disinfectants, namely, chloride, ozone and both, allowed very good performances to monitor these priority compounds at the trace level. The proposed methodology proved to be a feasible alternative for polar compound analysis, showing to be easy to implement, reliable, sensitive and requiring a low sample volume to monitor short-chain aldehydes and ketones in drinking water matrices.     

Thermodynamics of nucleic acid bases and nucleosides in water from 25 to 55°C

Specific heat capacities, apparent molar heat capacities, densities, and apparent molar volumes have been determined for cytosine, uracil, thymine, adenine, cytidine, 2-deoxycytidine, uridine, thymidine and adenosine at temperatures from 25°C to 55°C. The results of these measurements have been used to calculate for the first time, the thermodynamic quantities:C _p,2 ^o , (C _p,2 ^o /T)_p, (² C _p,2 ^o T ²)_p,V ₂ ^o , (V ₂ ^o /T)_p, and (² V ₂ ^o /T ²)_p. The-CH₂-group contribution has been calculated at different temperatures. It has also been observed from the data for the nucleic acid bases and nucleosides that the additivity ruleC _p,2 ^o (nucleoside)-C _p,2 ^o (base) +C _p,2 ^o (water)=C _p,2 ^o (ribose) does not hold in these cases.     

Indium/copper-mediated conjugate addition of unactivated alkyl iodides to α,β-unsaturated carbonyl compounds in water

An efficient method for the conjugate addition of unactivated alkyl iodides to α,β-unsaturated carbonyl compounds using indium/copper in water is described. The reactions proceed more efficiently in water than in organic solvents. In, CuI, and InCl₃ are all essential for efficient reaction. Formation of a symmetrical vic-diarylalkane is observed when an aryl-substituted alkene is used as substrate.     

Determination of 13 endocrine disrupting chemicals in sediments by gas chromatography–mass spectrometry using subcritical water extraction coupled with dispersed liquid–liquid microextraction and derivatization

In this study, a sample pretreatment method was developed for the determination of 13 endocrine disrupting chemicals (EDCs) in sediment samples based on the combination of subcritical water extraction (SWE) and dispersed liquid–liquid microextraction (DLLME). The subcritical water that provided by accelerated solvent extractor (ASE) was the sample solution (water) for the following DLLME and the soluble organic modifier that spiked in the subcritical water was also used as the disperser solvent for DLLME in succession. Thus, several important parameters that affected both SWE and DLLME were investigated, such as the extraction solvent for DLLME (chlorobenzene), extraction time for DLLME (30 s), selection of organic modifier for SWE (acetone), volume of organic modifier (10%) and extraction temperature for SWE (150 °C). In addition, good chromatographic behavior was achieved for GC–MS after derivatisation by using N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA). As a result, proposed method sensitive and reliable with the limits of detection (LODs) ranging from 0.006 ng g⁻¹ (BPA) to 0.639 ng g⁻¹ (19-norethisterone) and the relative standard deviations (RSDs) between 1.5% (E2) and 15.0% (DES). Moreover, the proposed method was compared with direct ASE extraction that reported previously, and the results showed that SWE–DLLME was more promising with recoveries ranging from 42.3% (dienestrol) to 131.3% (4,5α-dihydrotestosterone), except for diethylstilbestrol (15.0%) and nonylphenols (29.8%). The proposed method was then successfully applied to determine 13 EDCs sediment of Humen outlet of the Pearl River, 12 of target compounds could be detected, and 10 could be quantitative analysis with the total concentration being 39.6 ng g⁻¹, and which indicated that the sediment of Humen outlet was heavily contaminated by EDCs.     

Gas chromatography – inductively coupled plasma – time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental water samples

The application of inductively coupled plasma – time-of-flight mass spectrometry for the speciation analysis of organolead compounds in environmental waters is described. Construction of the transfer line was achieved by means of a relatively simple and rapid coupling procedure. Derivatization of the ionic lead species was achieved by in-situ propylation with sodium tetrapropylborate; simultaneous extraction of the derivatized compounds in hexane was followed by separation and detection by capillary gas chromatography hyphenated to inductively coupled plasma–time-of-flight mass spectrometry. Detection limits for the different organolead species ranged from 10 to 15 fg (as Pb), corresponding to procedural detection limits between 50 and 75 ng L^–1, on the basis of a 50 mL snow sample, extraction with 200 μL hexane, and subsequent injection of 1 μL of the organic extract on to the column. The accuracy of the system was confirmed by additional analysis of the water samples by capillary gas chromatography coupled with microwave-induced plasma–atomic-emission spectrometry and the analysis of a standard reference material CRM 605 (road dust) with a certified content of trimethyllead.     

Dispersive liquid–liquid microextraction using an in situ metathesis reaction to form an ionic liquid extraction phase for the preconcentration of aromatic compounds from water

A novel microextraction method is introduced based on dispersive liquid–liquid microextraction (DLLME) in which an in situ metathesis reaction forms a water-immiscible ionic liquid (IL) that preconcentrates aromatic compounds from water followed by separation using high-performance liquid chromatography. The simultaneous extraction and metathesis reaction forming the IL-based extraction phase greatly decreases the extraction time as well as provides higher enrichment factors compared to traditional IL DLLME and direct immersion single-drop microextraction methods. The effects of various experimental parameters including type of extraction solvent, extraction and centrifugation times, volume of the sample solution, extraction IL and exchanging reagent, and addition of organic solvent and salt were investigated and optimized for the extraction of 13 aromatic compounds. The limits of detection for seven polycyclic aromatic hydrocarbons varied from 0.02 to 0.3 μg L⁻¹. The method reproducibility produced relative standard deviation values ranging from 3.7% to 6.9%. Four real water samples including tap water, well water, creek water, and river water were analyzed and yielded recoveries ranging from 84% to 115%.      

Application of dynamic liquid-phase microextraction and injection port derivatization combined with gas chromatography–mass spectrometry to the determination of acidic pharmaceutically active compounds in water samples

A method has been established for the determination of four pharmaceutically active compounds (ibuprofen, ketoprofen, naproxen and clofibric acid) in water samples using dynamic hollow fiber liquid-phase microextraction (HF/LPME) followed by gas chromatography (GC) injection port derivatization and GC–mass spectrometric (MS) determination. Dynamic HF/LPME is a novel approach to microextraction that involves the use of a programmable syringe pump to move the liquid phases participating in the extraction so as to facilitate the process. Trimethylanilinium hydroxide (TMAH) was used as derivatization reagent for the analytes to increase their volatility and improve chromatographic separation. Parameters that affect extraction efficiency (selection of organic solvent, volume of organic solvent, agitation in the donor phase, plunger movement and extraction time) were investigated. Under optimal conditions, the proposed method provided good enrichment factors up to 251, reproducibility ranging from 3.26% to 10.61%, and good linearity from 0.2 to 50 μg/L. The limits of detection ranged between 0.01 and 0.05 μg/L (S/N = 3) using selective ion monitoring. This method was applied to the determination of the four pharmaceutically active compounds in tap water and wastewater collected from a drain in the vicinity of a hospital.     

How to estimate moments and quantiles of environmental data sets with non-detected observations? A case study on volatile organic compounds in marine water samples

Concentrations of 27 priority volatile organic compounds were measured in water samples of the North Sea and Scheldt estuary during a 3-year monitoring study. Despite the use of a sensitive analytical method, a number of data were censored. That is, some concentrations were below the decision limit or critical level defined by IUPAC. To characterize the observed measurement results, an attempt was made to identify an appropriate procedure to compute summary statistics for the censored data sets. Several parametric and robust parametric approaches based on the maximum likelihood principle and probability-plot regression method were evaluated for the estimation of the mean, standard deviation, median and interquartile range using three uncensored analytes (1,1,2-trichloroethane, tetrachloroethene and o-xylene) from the monitoring survey. Performance was assessed by artificially censoring the observed concentrations and estimating moments and quantiles at each censoring level. Results showed that methods with the least distributional assumptions, such as the robust bias-corrected restricted maximum likelihood method, perform best for estimating the mean and standard deviation, while both parametric and robust parametric techniques can be used for quantiles. Hence, summary statistics could be estimated with little bias (5-10%) up to 80% of censoring for the data sets employed in this study.     

Determination and mathematical modelling of budesonide solubility in N-methyl-2-pyrrolidone + water mixtures from T = 293.2 to 313.2 K

The solubilities of budesonide (BDS) in binary aqueous mixtures of N-methyl-2-pyrrolidone at temperatures ranging from 293.2 to 313.2 K were determined and mathematically correlated by three cosolvency models, i.e. Jouyban–Acree model, Jouyban–Acree–van’t Hoff model and modified Wilson model. The solubilities were measured using the shake-flask method and the models wereused to fit the solubility data of BDS in the solvent mixtures. The obtained mean relative deviations (MRDs %) for cosolvency models trained using whole data points varied between 5.0% and 31.0%. Solubilities were also predicted by the generally trained version of the Jouyban–Acree model with the MRD of 37.0%. Furthermore, the apparent thermodynamic properties of dissolution process of BDS in all the mixed solvents were calculated according to van’t Hoff and Gibbs equations. Dissolution of BDS in these mixed solvents is an endothermic process.     

Copper(II)-catalyzed silyl conjugate addition to α,β-unsaturated conjugated compounds: Brønsted base-assisted activation of Si-B bond in water

A mild method for the installation of the dimethylphenylsilyl group on the β-carbon of electron-deficient olefins is reported. In the presence of a catalytic amount of copper(II) (1 mol %) and amine base (5 mol %) at rt, the transformation proceeds efficiently in water within 1.5-5 h to afford β-silylated products in yields of up to 90%.     

Conjugates of polyhedral boron compounds with carbohydrates 7. Hydrolytic stability of closo-ortho-carborane glycoconjugates containing from one to three β-lactosylamine and β-d-galactopyranosylamine residues; estimation of their galectin-binding efficiency with galectin RCA120

The galectin-binding efficiency (Ricinus communis agglutinin, RCA) and the degree of deboronation at 37 °C of glycoconjugates of ortho-carboranylacetic acid containing from one to three β-lactosylamine or β-d-galactopyranosylamine residues were estimated; the glycoconjugates are potential agents for boron neutron capture therapy of cancer. Over a period of 24 h, up to ～15% of glycoconjugates underwent deboronation to give glycoconjugates of nido-ortho-carborane. With Lac-β-NH(COCH₂NH)₂COCH₂-o-CCHB₁₀H₁₀ as an example, it was demonstrated that the deboronation occurs at both 60 and 5 °C. Glycoconjugates with an O-linked β-galactose as a fragment of lactosylamine bind to galectin RCA₁₂₀ much more efficiently (up to ～40 times) than do the corresponding glycoconjugates with a N-linked β-galactose residue. The glycoconjugates containing one β-lactosylamine residue bind to galectin RCA approximately two times less efficiently than does lactose; however, introduction of the second and third β-lactosylamine residues into the glycoconjugate increases the binding efficiency by a factor of five to seven due to the cluster effect.     

Photochemistry of compounds in the constrained medium cellulose—part 8. Long-range electron transfer from excited pyrene to Cu(II) cation

Steady state spectroscopic techniques and laser flash photolysis have been used to investigate the photo-induced electron transfer from pyrene to cupric ions in cellophane films. The data indicate that the rate constant k(r) as a function of reactant separation r is given by k(r)=5×10¹¹exp(-0.61r)s^-1at 20°C. The rate constant decreases by a factor of 5 over the temperature range 20°C to -60°C which is attributed to a change of the adsorbed water in the cellophane; it then remains almost constant to 77 K.     

Solubility of budesonide in {ethanol + water} mixtures from T = (293.2 to 313.2) K: Experimental measurement and mathematical modelling

The solubility of budesonide (BDS) in binary mixtures of ethanol and water at T = (293.2–313.2) K is determined and mathematically represented using two cosolvency models, i.e. Jouyban–Acree model and Jouyban–Acree–van’t Hoff model. The mean relative deviations for fitting the solubility data of BDS in binary mixtures of ethanol + water are 6.6% and 6.5%, respectively. Furthermore, the apparent thermodynamic properties, dissolution enthalpy, dissolution entropy, and Gibbs free energy change of dissolution process of BDS in all the mixed solvents were calculated according to van’t Hoff and Gibbs equations. Dissolution of BDS in these mixed solvents is an endothermic process.     

Occupational exposure to complex mixtures of volatile organic compounds in ambient air: desorption from activated charcoal using accelerated solvent extraction can replace carbon disulfide?

A desorption study of 57 volatile organic compounds (VOCs) has been conducted by use of accelerated solvent extraction (ASE) and gas chromatography–mass spectrometry. Different solvents were tested to extract activated charcoal tubes with the objective of replacing carbon disulfide, used in official methods, because of its highly toxic health and environmental effects. Extraction conditions, for example temperature and number of cycles, were investigated and optimized. The definitive extraction procedure selected was use of acetone at 150 °C and two consecutive extraction cycles at a pressure of 1,500 psi. Considering a sample volume of 0.005 Nm³, corresponding to a sampling time of 8 h at a flow rate of 0.01 L?min^?1, the method was validated over the concentration range 65–26,300 μg?Nm^?3. The lowest limit of quantification was 6 μg?Nm^?3, and recovery for the 93 % of analytes ranged from 65 to 102 %. For most of the compounds, relative standard deviations were less than 15 % for inter and intra-day precision. Uncertainty of measurement was also determined: the relative expanded uncertainty was always below 29.6 %, except for dichlorodifluoromethane. This work shows that use of friendlier solvent, for example acetone, coupled with use of ASE, can replace use of CS₂ for chemical removal of VOCs from activated charcoal. ASE has several advantages over traditional solvent-extraction methods, including shorter extraction time, minimum sample manipulation, high reproducibility, and less extraction discrimination. No loss of sensitivity occurs and there is also a salutary effect on bench workers’ health and on the smell of laboratory air.