Coupling of a Modified In-Tube Solid Phase Microextraction Technique with High Perfor- mance Liquid Chromatography-Fluorescence Detection for the Ultra-Trace Determination of Polycyclic Aromatic Hydrocarbons in Water Samples

A modified in-tube solid phase microextraction (SPME) technique in conjunction with a high performance liquid chromatography (HPLC) was developed for the trace determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. The extraction device contained a regular HPLC syringe, replacing the metallic needle by two concentric fused silica capillary tubes. The capillary tubes were coated with polydimethylsiloxane (PDMS) as the sorbent and were attached to the syringe by a homemade interface made from polyether ether ketone (PEEK). The sorption of analytes was achieved by frequent withdrawing and ejecting the water sample from/into a vial via the capillary tubes. For the desorption step, an aliquot of organic solvent was withdrawn and subsequently injected directly into the HPLC system. Limits of detection for the elected PAHs were between 0.001 and 0.006 g L^–1 with a RSD of 2.6–6.3%.     

Mechanisms of antioxidant action: The catalytic rôle of iodine in the stabilisation of polypropylene

It is shown that I₂ is an effective melt stabiliser for polypropylene at 190°C in a closed mixer but that it is much less effective in an open mixer. The formation of HI and unsaturation in the polymer show that a catalytic antioxidant mechanism (CB-A/CB-D) is involved in the antioxidant activity of I₂ in a closed mixer similar to that occurring in the stabilisation of polyolefins with galvinoxyl and nitroxyl radicals.The processed polymer shows slightly greater uv stability than the control with no additive but is essentially similar to the control in thermal oxidative stability. The volatility of HI in an air oven probably accounts for the fact that it has no CB-D activity under these conditions.     

KMnO<Subscript>4</Subscript>/HOAc system promoted one-pot synthesis of benzoxazoles from <Emphasis Type="Italic">o</Emphasis>-aminophenols or oxidative cyclization of <Emphasis Type="Italic">o</Emphasis>-hydroxyarylidene anilines at room temperature

1,3-Benzoxazoles via oxidative cyclization of corresponding o-hydroxyarylidene anilines was synthesized in the presence of KMnO₄/HOAc system. This system also was applied for the one-pot synthesis of 1,3-benzoxazoles from o-amino phenols and aldehydes. The both protocols were processed at room temperature under solvent-free conditions with good to excellent yields.     

Liquid-liquid-liquid microextraction followed by HPLC with UV detection for quantitation of ephedrine in urine

Liquid-liquid-liquid microextraction (LLLME) in combination with HPLC and UV detection has been used as a sensitive method for the determination of ephedrine in urine samples. Extraction process was performed in a homemade total glass vial without using a Teflon ring, usually employed. Ephedrine was first extracted from 3.5 mL of urine sample (pH 12) into a microfilm of toluene/benzene (50:50). The analyte was subsequently back extracted into an acidic microdrop solution (pH 2) suspended in the organic phase. The extract was then injected into the HPLC system directly. An enrichment factor of 137 along with a good sample clean-up was obtained under the optimized conditions. The calibration curve showed linearity in the range of 0.01-50 mg/L with regression coefficient corresponding to 0.998. The LODs and LOQs, based on a S/N of 3 and 10, were 5 and 10 microg/L, respectively. The method was eventually applied for the determination of ephedrine in urine sample after oral administration of 5 mg single dose of drug.     

A superhydrophobic silica aerogel with high surface area for needle trap microextraction of chlorobenzenes

Microchimica Acta - The authors have synthesized a superhydrophobic silica aerogel by using a sol-gel technique. The material is shown to be an efficient sorbent for needle trap microextraction of...     

Solvent-free synthesis of highly functionalized indole-based 4,5-dihydrofurans and evaluation of their antioxidant activity

Facile and efficient diastereoselective synthesis of trans-indolyldihydrofurans by three-component reaction of 3-cyanoacetyl indoles with various aromatic aldehydes and N-phenacylpyridinium bromides in presence of 1,1,3,3-N,N,N′,N′-tetramethylguanidine under solvent-free conditions is described. This ecofriendly protocol offers several advantages such as a cost-effective procedure with excellent yield, short reaction time, ease workup and product isolation, good functional group tolerance, and broad scope of usable substrates. The synthesized compounds were also evaluated for their antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay.     

On-line Micro Solid-Phase Extraction of Clodinafop Propargyl from Water,Soil and Wheat Samples Using Electrospun Polyamide Nanofibers

An on-line extraction/determination set up was designed for micro solid-phase extraction of clodinafop propargyl from water, soil and wheat samples using electrospun polyamide nanofiber mats. The prepared mats were packed in a stainless steel tube which conveniently acted as a high-performance liquid chromatography injection loop. Influential parameters affecting the extraction efficiency were optimized using a distilled water sample fortified with 25 μg L^?1 of clodinafop propargyl. An enrichment factor of 440 was achieved for clodinafop propargyl indicating the ability of the whole procedure. Under the optimum conditions, the linearity for the analyte was in the range of 6–700 μg L^?1, while a limit of detection and limit of quantification of 2 and 6 μg L^?1 were achieved, respectively. The intra-day and inter-day RSD% at the concentration level of 25 μg L^?1 were 4.6 and 9.3 %, respectively. To investigate the matrix effect, the developed method was applied to the analysis of real water samples including paddy and river waters as well as the wheat and soil samples. The relative recovery percentages for the spiked samples were in the range of 63–95 %.     

Electroentrapment of Polyaniline in [3-(2,3-Epoxypropoxy)propyl]trimethoxysilane-Derived Xerogel: A Facile Methodology Towards Molecularly Imprinted Xerogels

A novel polyaniline (PANI)/silica hybrid composite, as a selective coating, was synthesized by the simultaneous sol–gel process and in situ electro-polymerization of aniline and employed for imprinting naproxen. The synthesized composite was chemically bonded inside a copper tube for online capillary microextraction (CME) in combination with high-performance liquid chromatography (HPLC). The copper tube was intended for use as an unbreakable substrate for CME and the HPLC injection loop. Four copper tubes containing different coatings were prepared accordingly to achieve the most appropriate extracting medium for naproxen. Coating 1 was a xerogel of [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (EPPTMOS) synthesized by sol–gel technology and PANI as a conductive polymer (CP) was electrochemically prepared as coating 2. Coating 3 (sol–gel–CP) included the electroentrapped PANI into the xerogel of EPPTMOS, representing the non-imprinted xerogel (NIX) and coating 4, the molecularly imprinted xerogel (MIX), contained entrapped PANI into the xerogel of EPPTMOS, while naproxen template was already imprinted into the composite structure. Extraction efficiency of MIX towards naproxen was about 4–30 times greater than the others. Electroentrapped PANI into the silica xerogel might be responsible for the enhanced extraction efficiency, originating from high surface area of PANI as well as its role in π–π interactions. The mild conditions used in this process enabled the incorporation of organic species such as PANI into the silica particles without degradation. The main advantage of addition of PANI during the sol–gel process was the reduction of gelation time from more than a week to a few hours and, therefore, achieving a facile and controllable method for preparation of selective media. Furosemide, clodinafop-propargyl and haloxyfop-etotyl were also selected to investigate selectivity of the prepared MIX towards naproxen. Ratio of MIX/NIX, a criterion of selectivity, was 3.8, 1.1, 1.2, and 1.4 for naproxen, clodinafop, haloxyfop and furosemide, respectively. The linearity of the HPLC method for naproxen was in the range of 10–1,000 µg L^?1. The limit of detection value was found to be 5 µg L^?1 and RSD % of 2.9 (n = 5) was obtained. Real samples such as blood plasma and urine species were analyzed by the developed method and the relative recovery percentages of 76 and 94 % were obtained for the spiked samples.     

Electrospun polyamide–polyethylene glycol nanofibers for headspace solid‐phase microextration

A solution of polyamide (PA) containing polyethylene glycol (PEG) as a side low‐molecular‐weight polymer was electrospun. After synthesizing the PA–PEG nanofibers, the constituent was subsequently removed (modified PA) and confirmed by Fourier transform infrared spectroscopy. The scanning electron microscopy images showed an average diameter of 640 and 148 nm for PA and PA–PEG coatings, respectively, while the latter coating structure was more homogeneous and porous. The extraction efficiencies of PA, PA–PEG, and the modified PA fiber coatings were assayed by headspace solid‐phase microextraction of a number of chlorophenols from real water samples followed by their determination by gas chromatography with mass spectrometry. To prepare the most appropriate coatings, the amounts and the flow rate of the electrospinning solution were investigated. Various extraction parameters, such as the salt content, desorption condition, extraction temperature, and time were optimized. The limits of detection of the method were in the range of 0.8–25 ng/L, while the RSDs at two concentration levels of 200 and 80 ng/L were between 2.1 and 12.2%. The analysis of real water samples led to relative recoveries between 85 and 98% with a linearity of 8–1500 ng/L.