Microwave-assisted polycondensation of aliphatic diols of isosorbide with aliphatic disulphonylesters via phase-transfer catalysis

Numerous polycondensations of aliphatic diol of isosorbide and 1,8-dimesyloctane or other aliphatic dibromo and disulphonated alkylating agent was performed under phase-transfer catalytic conditions. In order to check the possible specific non-thermal microwave (MW) effects, reactions were comparatively performed inside a thermostated oil bath (Δ) under similar conditions. The reactions conditions were varied to optimize both, the fraction insoluble in methanol (FP MeOH) and the molecular weight of polyethers. In all cases, it was found that microwave-assisted polycondensations proceeded more efficiently compared with conventional heating (the reaction time was reduced from 24 h to 30 min: ratio 1/50). The polycondensation under microwave yields 63% of polyethers precipitating in methanol with relatively high average-weight molecular weights (M_w up to approximately 7000). The polyethers were characterized by NMR (¹H, ¹³C) and FT-IR spectroscopy and SEC measurement and MALDI-TOF mass spectrometry.     

In-drop derivatisation liquid-phase microextraction assisted by ion-pairing transfer for the gas chromatographic determination of phenolic endocrine disruptors

A novel in-drop derivatisation liquid-phase microextraction procedure with an ion-pairing agent is developed and optimised for the extraction of endocrine-disrupting chemicals. The ethyl esters of the analytes were rapidly formed in the organic drop and analysed by gas chromatography. The effects of various parameters such as rate and time of agitation, ion-pairing agent and reactant concentration, pH and temperature were studied systematically to optimise the process and bring out the locale of reaction in the organic drop. A study of the mechanistic pathways of the overall procedure is attempted leading to interesting findings and delineating important points of the kinetics and mechanism. A mechanistic model is proposed on the basis of the theory of mass transfer with chemical reaction in two liquid phases. The O-ethoxycarbonyl derivatisation appears to take place in the bulk organic phase. The system provides insight into the first reported analytical case of single-drop extraction-preconcentration-derivatisation assisted by an ion-pairing transfer and has all of the interesting facets of chemical reaction in which the role of mass transfer comes into picture.The analytical features of the method are acceptable and the overall relative standard deviations of the intra-day repeatability (n = 5) and inter-day reproducibility were <3.9% and <5.4%, respectively, for gas chromatography-mass spectrometry analyses and <4.3% and <7.1% for gas chromatography-flame ionisation detection analyses. The method was applicable to urine and surface water samples. The LODs ranged between 0.2-1.3 ng mL⁻¹ and 8.5-26.5 ng mL⁻¹ for GC/MS and GC/FID analyses, respectively.     

Comparative study of analytical methods involving gas chromatography-mass spectrometry after derivatization and gas chromatography-tandem mass spectrometry for the determination of selected endocrine disrupting compounds in wastewaters

Two GC-MS methods, based on the application of N,O-bis(trimethylsilyl)trifluoroacetamide-derivatization-GC-MS (selected-ion monitoring) and GC-MS-MS without derivatization, respectively, were optimised and applied to the determination of a group of five selected endocrine disrupting compounds (EDCs) in wastewaters. Both methods included solid-phase extraction with Oasis HLB cartridges allowing an enrichment factor for wastewater samples of 100-fold. The investigated EDCs were estrone, 17beta-estradiol, 17alpha-ethynylestradiol, 4-tert-octylphenol and bisphenol A. Results obtained from the validation studies yielded comparable results in both cases. Recoveries in spiked wastewaters at 50 ng/l were higher than 90% for all the compounds, except for 4-tert-octylphenol (75%). Repeatability and reproducibility were adequate, varying from 1.6 to 14%, except for estrone which reproducibility was 28% when the derivatization-GC-MS method was applied. Limits of detection calculated ranged from 2.5 to 27.5 ng/l with differences between both methods from 1.1 (estrone) to 10.4 (bisphenol A) times. Both methods were successfully applied to the analysis of the target compounds in sewage treatment plant influents and effluents. Traces of bisphenol A, 4-tert-octylphenol, estrone and 17beta-estradiol were detected at concentration levels ranging from 13.3 to 1105.2 ng/l.     

Microwave-assisted silylation followed by gas chromatography/mass spectrometry for rapid determination of ergosterol in cigarettes

Ergosterol is one of the important precursors of tumorigenic polynuclear aromatic hydrocarbons. To the best of our knowledge, a large amount of ergosterol is present in moldy cigarettes, which derives from fungal contaminations. Thus, the development of a simple, fast, and efficient method for the analysis of ergosterol is in great demand. In this paper, GC/MS following microwave-assisted silylation (MAS) was developed for the rapid quantitative analysis of ergosterol in cigarettes for the first time. In our work, total ergosterol in cigarettes after NaOH saponification was extracted with hexane, and then was fast derivatized with bis(trimethylsilyl)trifluoroacetamide (BSTFA) under microwave irradiation. Finally, the ergosterol trimethylsilyl derivative was analyzed by GC/MS. Derivatization conditions including microwave reaction solvent, irradiation time, and power were investigated. Method validations (linear range, LOD, precision, and recovery) were also studied. The results showed that the proposed method provided a fast, simple, and sensitive approach for the determination of ergosterol in cigarettes. Finally it was successfully applied to the analysis of ergosterol in normal and mildewy cigarettes.     

Precolumn fluorogenic labelling of carboxylic acids with the use of N-(1-pyrenyl)-bromoacetamide and phase-transfer catalysis

Summary N-(1-Pyrenyl)-bromoacetamide, which is readily synthesized from 1-aminopyrene and bromoacetyl bromide, has proved to be an excellent derivatization reagent for carboxylic acids. A technique has been developed, based upon a reaction with the carboxylate as an ion pair in ethylene dichloride at 90 °C, which gives highly fluorescent ester derivatives, permitting quantitative determination by liquid chromatography of less than one pmol using conventional fluorimetric detection. Further, the method is highly reproducible and of general utility.     

Comparative study of chemically immobilized and conventional homogeneous ionic liquids as phase-transfer catalysts for the N-alkylation of heterocyclic compounds

Various ionic liquids (ILs) were screened for their phase-transfer catalytic (PTC) activity using the N-alkylation of nitrogen heterocycles as the model reaction. Immobilized ILs behaved extremely well and proved to be far better catalysts than conventional homogeneous PTCs in terms of their stability, easy recovery, and reusability. The investigation also demonstrated that quaternary tetraalkylammonium salts offer very high catalytic activity, whereas aromatic heterocyclic tetravalent nitrogen catalysts (imidazolium- and pyridinium-based salts) were poorly active.     

Analytical methods for the determination of selected steroid sex hormones and corticosteriods in wastewater

An analytical method for the determination of 12 selected estrogens, progestagens and corticosteroids is presented. The optimization of the method, including liquid chromatography separation, extraction on a solid phase, purification on a silica gel cartridge and detection by mass spectrometry, is described. Both the repeatability, with relative standard deviation ranging from 1.4 to 2.7%, and the accuracy, with recoveries ranging from 92.7 to 102.4%, were very satisfactory for ten of the target analytes. The limits of detection were lower than 1 ng/L for progestagens, androgens and corticosteroids, and ranged between 0.9 and 4.3 ng/L for estrogens. The results of the analysis of two sewage treatment plants in the area of Lyon (France) by this method reveal that all the compounds investigated are present in the effluents. The estrogen most frequently detected was estrone, with a median of 26.1 ng/L. The target progestagens were detected with concentrations ranging between 5 and 41 ng/L. Androgens were also present in most of the samples in the range 1–30 ng/L, while the corticosteroids were present only in one plant, with a median of 31.9 ng/L.     

A rapid gas chromatographic method for the determination of diazepam and metabolites in body fluids

A rapid method is described for the extraction of diazepam and its metabolites from plasma and urine. The procedure is applicable to subsequent analysis by electron capture gas chromatography, and has been used for the analysis of clinical samples. The detection limit for diazepam is about 0.01 μg/ml, using a 2-ml sample. Quantification of lower levels of benzodiazepines requires a sample clean-up procedure, and the method is not suitable for this purpose.     

Liquid chromatographic trace enrichment with on-line capillary gas chromatography for the determination of organic pollutants in aqueous samples

Trace enrichment for the GC analysis of a series of chlorinated pesticides and polychlorinated biphenyls (PCBs) in aqueous samples has been achieved through a simple on-line technique involving sorption on an LC micro-precolumn followed by direct elution into a gas chromatograph with hexane. A 5-m retention gap coupled to the capillary GC column served as the recipient of a relatively large sample volume (ca. 100 μl) introduced into the GC. Partially concurrent solvent evaporation during sample introduction allowed a large sample capacity. Recoveries of more than 95% were observed for the majority of the compounds studied. Using 1.0 ml aqueous samples, detection limits of less than 1 ppt were found. The applicability of the developed method was demonstrated for a river water sample.     

A rapid gas chromatographic method for the determination of chlorophenoxyisobutyric acid in plasma and urine.

A rapid gas chromatographic method is described for the determination of chlorophenoxyisobutyric acid (the active metabolite of clofibrate) in plasma and urine. The assay involves an extraction into toluene and back-extraction of the chlorophenoxyisobutyric acid and the internal standard (2-naphthoic acid) into the methylating reagent (trimethylanilinium hydroxide). Concentrations of 1 mug/ml in plasma and urine can easily be measured; the precision of the method is 3.3 +/- 0.7% for plasma and 2.7 +/- 0.4% for urine. There is no interference from endogenous compounds or from drugs commonly prescribed together with clofibrate.     

Microwave-assisted headspace solid-phase microextraction for the rapid determination of organophosphate esters in aqueous samples by gas chromatography-mass spectrometry

The rapid and solvent-free determination of organophosphate esters (OPEs) in aqueous samples via one-step microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analysis is described. Tri-n-butyl phosphate (TnBP) and tris-(2-ethylhexyl) phosphate (TEHP) were selected as model compounds for the method of development and validation. The effects of various extraction parameters for the quantitative extraction of these analytes by MA-HS-SPME were systematically investigated and optimized. The analytes, in a 20 mL water sample (in a 40 mL sample bottle containing 2 g of NaCl, pH 3.0), were efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the system was microwave irradiated at 140 W for 5 min. The limits of quantification (LOQs) for TnBP and TEHP were 0.5 and 4 ng/L, respectively. Using the standard addition method, MA-HS-SPME coupled with GC-MS was utilized to determine selected OPEs in surface water and wastewater treatment plants (WWTP) influent/effluent samples. Preliminary results show that TnBP was commonly detected OPEs in these aqueous samples, the correlation coefficients (r²) of the standard addition curves were greater than 0.9822, indicating that the developed method appears to be a good alternative technique for analyzing OPEs in aqueous samples.     

Ethyl acetate for the desorption of a liquid chromatographic precolumn on-line into a gas chromatograph

The feasibility of using ethyl acetate for the desorption of trace pollutants from a liquid chromatographic precolumn on-line into a diphenyltetramethyldisilazane-deactivated retention gap and, subsequently analysis by means of capillary gas chromatography has been demonstrated. First 5% of methanol are added to the water sample to prevent sorption of analytes onto parts of the preconcentration system. About 1 ml of this aqueous sample is injected onto a precolumn containing a polymeric stationary phase, using water–methanol (95:5, v/v) for transport and clean-up. The precolumn is desorbed with ethyl acetate and a fraction of 75 μl is injected on-line into the retention gap; separation is then achieved on a capillary CP Sil 19 column. No breakthrough of the test compounds was observed in the preconcentration step. The recovery was quantitative and the response obtained with flame ionization detection was linear in the range 0.1–100 ng/ml. The effect of varying the sorption flow rate on the recovery was studied. The system was applied to the analysis of river water.     

An integrated high resolution mass spectrometric and informatics approach for the rapid identification of phenolics in plant extract

An integrated approach based on high resolution MS analysis (orbitrap), database (db) searching and MS/MS fragmentation prediction for the rapid identification of plant phenols is reported. The approach was firstly validated by using a mixture of phenolic standards (phenolic acids, flavones, flavonols, flavanones, flavanols, isoflavones). In particular, the integrated approach consists of the following steps: (1) LC-ESI-MS/MS analysis in data dependent scan mode using an orbitrap mass analyzer (resolution 60,000; positive ion-mode, ESI source); (2) searching the experimental monoisotopic masses (tolerance 1 ppm) in plant phenols databases; (3) filtering the entries on the basis of the phenol class to which the unknown belongs, as determined on the basis of the UV spectrum. Final identification is achieved by matching the isotopic pattern and by MS/MS fragmentation studies. In particular, experimental MS/MS fragments are matched with those predicted by a commercially available software. The method was then successfully applied for the rapid identification of phenolics contained in an EtOH extract of Angelica keiskei.     

Development of a methodology utilizing gas chromatography ion-trap tandem mass spectrometry for the determination of low levels of caffeine in surface marine and freshwater samples

A methodology for monitoring low level of caffeine in aqueous samples via gas chromatography coupled with an ion-trap tandem mass spectrometry detection system (IT-MS/MS) was developed. Four IT-MS/MS operating parameters, including the collision-induced dissociation (CID) voltage, the excitation time (ET), the isolation time (IT) and the maximum ionization time (MIT) were optimized in order to maximize the sensitivity of the IT-MS/MS technique towards the analyte and its isotope-labeled standard. After optimization, a limit of detection of 500 fg μl⁻¹ with S/N = 3 was achieved. Taking into account blank values and the matrix background, a method detection limit of 1.0–2.0 ng l⁻¹ was derived and applied to all of the samples analyzed in the study. Various mass spectrometric conditions have been applied to caffeine and its trimethyl-¹³C-labeled standard to elucidate fragmentation pathways for new and commonly occurring product ions observed in the collision-induced dissociation (CID) spectra produced by the ion trap. Ion structures and fragmentation pathway mechanisms have been proposed and compared with previously published data. An isotope dilution method using ¹³C-labeled caffeine as a surrogate internal standard was employed to determine and correct the recovery of native caffeine in water samples. The developed methodology has been applied for the determination of caffeine in surface marine and freshwater samples collected on the west coast of Vancouver Island in British Columbia, Canada. The results obtained for the marine water samples indicated a wide variation in the level of caffeine, ranging from 4.5 to 149 ng l⁻¹, depending on the location of the sampling site within the inlet. The concentrations of caffeine in samples from lakes associated with various residential densities ranged from ND to 6.5, 1.8 to 10.4 and 6.1 to 21.7 ng l⁻¹ for low, moderate and high residential densities, respectively.     

Imprinted silica nanoparticles coated with N‐propylsilylmorpholine‐4‐carboxamide for the determination of m‐cresol in synthetic and real samples

m‐Cresol‐imprinted silica nanoparticles coated with N‐propylsilylmorpholine‐4‐carboxamide have been developed that contain specific pockets for the selective uptake of m‐cresol. Silica nanoparticles were synthesized by a sol–gel process followed by functionalization of their surface with N‐propylsilylmorpholine‐4‐carboxamide. The formation of m‐cresol‐imprinted silica nanoparticles was confirmed by UV‐Vis spectrophotometry, infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and transmission electron microscopy. Electron microscopic studies revealed the formation of monodispersed imprinted silica nanoparticles with spherical shape and an average size of 83 nm. The developed nanoparticles were filled in a syringe and used for the extraction of m‐cresol from aqueous samples followed by quantification using high‐performance liquid chromatography with diode array detection. Various adsorption experiments showed that developed m‐cresol‐imprinted silica nanoparticles exhibited a high adsorption capacity and selectivity and offered a fast kinetics for rebinding m‐cresol. The chromatographic quantification was achieved using mobile phase consisting of acetonitrile/water (70:30 v/v) at an isocratic flow rate of 1.0 mL/min using a reversed‐phase C₁₈ column and detection at λ_max = 275 nm. The limits of detection and quantification were 1.86 and 22.32 ng/mL, respectively, for the developed method. The percent recoveries ranged from 96.66–103.33% in the spiked samples. This combination of this nanotechnique with molecular imprinting was proved as a reliable, sensitive and selective method for determining the target from synthetic and real samples.     

微波辅助消解-原子荧光法测定玻璃中的镉砷铅

光学玻璃中的各种元素对玻璃的光学性能有不同的影响。如加入镉可以提高玻璃折射率;砷的引入能增加玻璃的透光度,含铅玻璃具有低成本、高折射性等优点。但是镉、砷、铅均为有毒元素,玻璃加工和处理过程以及毒废弃物的处理都可能引起水、土壤、大气的污染并给人体带来一定的危害     

A rapid and efficient catalysis system for the synthesis of 4‐vinylbiphenyl derivatives

A series of 4‐vinylbiphenyl derivatives were synthesized by Pd(OAc)₂/PCy₃‐catalyzed Suzuki–Miyaura reaction in the presence of K₃PO₄.3H₂O as base in toluene at 80°C for only 10–30 min, and the corresponding products achieved 65–98% yields. According to this efficient C―C bond‐forming method, the obtained yields of 4‐vinylbiphenyl liquid crystal compounds were up to 92–96%. Copyright © 2013 John Wiley & Sons, Ltd.     

Inverse gas chromatographic and chemometric tools for determination of interactions between the components of polymeric composition

Compositions of polymers (polyethylene and polyuretane) and fillers (initial silica and silicas modified with: N-2-aminoethyl-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxy-silane, 3-merkaptopropyltrimethoxysilane, octyltriethoxysilane) were examined by inverse gas chromatography at 383 K. Small amounts of the following test solutes were injected to achieve the infinite dilution conditions: pentane, hexane, heptane, octane, nonane, dichloromethane, chloroform, carbon tetrachloride and 1,2-dichloroethane.The retention times for these test solutes were determined and Flory-Huggins parameters were calculated. Flory-Huggins parameters characterize interactions between components: - between composition and the test solute and χ^′23 - between polymer and filler in the composition.Values of both physicochemical parameters characterizing the examined materials were arranged in a matrix form: in the rows the compositions were enumerated at different temperatures whereas the columns contained the test solutes. After standardization the input matrix was subjected to principal component analysis. Three principal components explain more than 93% of the total variance in the data. Almost all test solutes carry very similar information. Therefore, it is justified to eliminate most of them from the series of test solutes.