Development of a simple and valid method for the trace determination of phthalate esters in human plasma using dispersive liquid–liquid microextraction coupled with gas chromatography–mass spectrometry

A new method was developed for the trace determination of phthalic acid esters in plasma using dispersive liquid–liquid microextraction and gas chromatography with mass spectrometry analysis. Plasma proteins were efficiently precipitated by trichloroacetic acid and then a mixture of chlorobenzene (as extraction solvent) and acetonitrile (as dispersive solvent) rapidly injected to clear supernatant using a syringe. After centrifuging, chlorobenzene sedimented at the bottom of the test tube. 1 μL of this sedimented phase was injected into the gas chromatograph for phthalic acid esters analysis. Different factors affecting the extraction performance, such as the type of extraction and dispersive solvent, their volume, extraction time, and the effects of salt addition were investigated and optimized. Under the optimum conditions, the enrichment factors and extraction recoveries were satisfactory and ranged between 820–1020 and 91–97%, respectively. The linear range was wide (50–1000 ng/mL) and limit of detection was very low (1.5–2.5 ng/mL for all analytes). The relative standard deviations for analysis of 1 μg/mL of the analytes were between 3.2–6.1%. Salt addition showed no significant effect on extraction recovery. Finally, the proposed method was successfully utilized for the extraction and determination of the phthalic acid esters in human plasma samples and satisfactory results were obtained.     

Efficient Detection of Phthalate Esters in Human Saliva via Fluorescence Spectroscopy

The detection of phthalates in human biologic fluids remains an important research objective because it provides an important measure of an individual’s exposure to this class of compounds, which have known deleterious health effects. Moreover, the ability to accomplish such detection in fluids that are easy to collect, such as saliva and urine, provides additional practical advantages. Reported herein is the application of cyclodextrin-promoted fluorescence energy transfer and fluorescence modulation to accomplish precisely such detection: the development of sensitive and selective florescence-based detection methods for phthalates in saliva, an easily collectable human biologic fluid. Such saliva-based detection methods occur with high levels of selectivity (100% differentiation) and sensitivity (limits of detection as low as 0.089?µM), and provide significant potential in the development of practical phthalate detection devices.     

Mathematical modeling of a slurry reactor for DME direct synthesis from syngas

In this paper,an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether(DME) from syngas.This large-scale reactor is modeled using mass and energy balances,catalyst sedimentation andsingle-bubble as well as two-bubbles class flow hydrodynamics.A comparison between the two hydrodynamic models through pilot plantexperimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data thanhomogeneous single-bubble gas flow model.Also,by investigating the heterogeneous gas flow and axial dispersion model for small bubblesas well as the large bubbles and slurry(i.e.including paraffins and the catalyst) phase,the temperature profile along the reactor is obtained.Acomparison between isothermal and non-isothermal reactors reveals no obvious performance difference between them.The optimum values ofreactor diameter and height were obtained at 7 m and 50 m,respectively.The effects of operating variables on the axial catalyst distribution,DME productivity and CO conversion are also investigated in this research.     

Efficient synthesis of multiply substituted furans using BF@Propyl/dopamine/Pd as a green catalyst

One of the commonly used methods to synthesize furans is the three-component reaction among aromatic aldehyde, arylamine, and acetylenedicarboxylate. The main advantages of this work are easy reaction work-up, short reaction time, high yield and easy recyclability, reusability of the catalyst. And also basalt fiber applications are surely innovative in many industrial and economic fields, because of its good mechanical, chemical and thermal performances.     

Silica Gel Catalyzed Conversion of Dimethyl 2-(5-Bromo-2-hydroxyphenyl)-3-(triphenylphosphoranylidene)butanedioate to Methyl 6-Bromo-2-oxo-2H-chromene-4-carboxylate in Solvent-Free Conditions

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dimethyl acetylenedicarboxylate, by 4-bromophenol leads to vinyltriphenylphosphonium salt, which undergoes aromatic electrophilic substitution reaction with conjugate base to produce dimethyl 2-(5-bromo-2-hydroxyphenyl)-3-(triphenylphosphoranylidene)butanedioate. Silica gel was found to catalyze conversion of dimethyl 2-(5-bromo-2-hydroxyphenyl)-3-(triphenylphosphoranylidene)butanedioate to methyl 6-bromo-2-oxo-2H-chromene-4-carboxylate in solvent-free conditions at 80°C in fairly high yield.     

Synthesis of oxo-Phosphoranylidene Aminobenzoic Acid Derivatives by a Multicomponent Reaction

2-Aminobenzoic acids or 4-aminobenzoic acid react with dimethyl acetylenedicarboxylate/triphenylphosphine in less than 20 min at 15–25°C to produce new organic phosphorus compounds in good to excellent yields. The conversion occurs with selective N- over O-alkylation of the amino group and isolation of the products is accomplished simply by filtration.     

Reaction of Dimethyl Acetylenedicarboxylate With 2-Mercaptoperimidine and 2-Mercaptobenzimidazole

A mixture of equimolar quantities of dimethyl acetylenedicarboxylate ( 2 ) with either 2-mercaptoperimidine ( 1 ) or 2-mercaptobenzimidazole ( 5 ) was heated in absolute benzene in the presence of triphenylphosphine as a catalyst under reflux conditions for 1 h (the reaction was monitored by TLC until the consumption of the starting materials). The solvent was concentrated under vacuum and the residue was subjected to chromatographic plates using toluene-ethylacetate (2:1) as an eluent. The products in each reaction were separated as two migrating zones. Each zone was removed from the plate and recrystallized from the appropriate solvent. The products of the first reaction are 10-methoxy-11-oxo-11H-8-thia-7,11a-diaza-benzo[de]anthracene-9-carboxylic acid methyl ester ( 3 ) and 8-thia-7,10a-diaza-cyclopenta[a]phenalene-9,10-dicarboxylic acid dimethyl ester ( 4 ), while the products of the second reaction are 3-methoxy-4-oxo-4H-1-thia-4a,9-diaza-fluorene-2-carboxylic acid methyl ester ( 10 ) and benzo[4, 5]imidazo[2,1-b]thiazole-2,3-dicarboxylic acid dimethyl ester ( 11 ). The mechanisms of the observed reactions are suggested.     

Polymers Derived from 4-Substituted Salicylic Acids as Antifungal Agents

4-Amino-, chloro-, and bromo-substituted salicylic acid-formaldehyde polymers and their metal chelates were screened for their antifungal activity. Various copolymers prepared from 4-chloro-(bromo)salicylic acid, formaldehyde, and other comonomers were also screened for their antifungal activity. All these polymers, copolymers, and polychelates were found active against several fungi Their fungicidal activities are compared with those of the corresponding monomers and monomeric chelates.     

Electron Spin Resonance Study on Grafting of Tetrafluoroethylene onto Polyethylene

An ESR study has been made on the course of grafting of tetrafluoroethylene onto polyethylene. Alkyl and allyl radicals trapped in the polymers were measured under various grafting conditions. It was observed that alkyl radicals decay very rapidly when monomers are in contact with the irradiated polymer, while allyl radicals decay very slowly even in the presence of monomers as in the decay of radicals in irradiated polymers without monomers. The effect of pre-irradiation temperature on grafting was also studied, and the rate of grafting was found to be much faster for lower pre-irradiation temperatures. From these experimental results it was concluded that alkyl radicals play an important Tole in the initiation reaction of grafting.