Determination of nickel using cold-induced aggregation microextraction based on ionic liquid followed by flame atomic absorption spectrometry

Cold-induced aggregation microextraction (CIAME) combined with flame atomic absorption spectrometry (FAAS) was applied to preconcentration and determination of nickel(II) ions in natural water samples. The proposed method used 1-hexyl-3-methylimidazolium hexafluorophosphate ([Hmim][PF ₆ ]) as the extraction solvent and 1-(2-thiazolylazo)-2-naphthol (TAN) as the complexing agent. The extraction solvent was dissolved in the sample solution at 45°C. After dissolving, the solution was cooled in the ice bath and a cloudy solution of IL fine droplets was formed due to the decrease of IL solubility. After centrifugation, the fine droplets of extractant phase were settled at the bottom of the conical-bottom centrifuge tube. Analysis was carried out by a FAAS. Several important parameters influencing the CIAME extraction efficiency such as pH, complexing agent concentration, extraction solvent volume, salt effect, solution temperature, extraction time, centrifugation time and heating time were investigated and optimized. Under the optimum conditions, the limit of detection (LOD) was 0.8 ng/mL, and the relative standard deviation (RSD) was 3.4% for 50 ng/mL of nickel. The performance of the method was evaluated for extraction and determination of nickel in tap, mineral and seawater samples, and satisfactory results were obtained.     

Using dispersive liquid-liquid microextraction and liquid chromatography for determination of guaifenesin enantiomers in human urine

A simple, rapid, and efficient method, dispersive liquid–liquid microextraction (DLLME) coupled with high‐performance liquid chromatography‐fluorescence detector, has been developed for the determination of guaifenesin (GUA) enantiomers in human urine samples after an oral dose administration of its syrup formulation. Urine samples were collected during the time intervals 0–2, 2–4, and 4–6 h and concentration and ratio of two enantiomers was determined. The ratio of R‐(?) to S‐(+) enantiomer concentrations in urine showed an increase with time, with R/S ratios of 0.66 at 2 h and 2.23 at 6 h. For microextraction process, a mixture of extraction solvent (dichloromethane, 100 μL) and dispersive solvent (THF, 1 mL) was rapidly injected into 5.0 mL diluted urine sample for the formation of cloudy solution and extraction of enantiomers into the fine droplets of CH₂Cl₂. After optimization of HPLC enantioselective conditions, some important parameters, such as the kind and volume of extraction and dispersive solvents, extraction time, temperature, pH, and salt effect were optimized for dispersive liquid–liquid microextraction process. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 10 to 2000 ng/mL for target analytes. LOD was 3.00 ng/mL for both of the enantiomers.     

A ionic liquid for dispersive liquid-liquid microextraction of phenols

In the present study, a new solvent-free mode of liquid phase microextraction termed ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) was developed. Four phenols were used as model compounds in the development and evaluation of the procedure. In this method, 50 μL of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF₆]) and 1.5 mL of sample aqueous solution were placed in a 2.2-mL glass test tube and mixed by aspirating and rapidly injecting by a syringe. This procedure produced a cloudy solution. In this process, phenols in the water sample were extracted into the IL phase. After centrifuging, the fine droplets of IL sedimented to the bottom of the glass test tube. The settled phase was injected into the high performance liquid chromatograph (HPLC) for separation and detection of phenols. Some parameters that might affect the extraction efficiency were optimized. The main advantages of the proposed method are high speed, high recovery, good repeatability and environmental friendliness.     

Comparison of efficiencies between single-drop microextraction and continuous-flow microextraction for the determination of methomyl in natural waters

Two liquid-phase microextraction (LPME) approaches, static direct-immersed single-drop microextraction (DI-SDME) and continuous-flow microextraction (CFME), were used to extract methomyl in water samples and their respective extraction efficiencies were compared. Several important parameters affecting extraction efficiency such as the type of extraction solvent, solvent drop volume, stirring speed or flow rate, extraction time and salt concentration were optimised. The optimised conditions were as follows: 3.0-µL tetrachloroethane (C₂H₂Cl₄) as the extraction solvent, 15% NaCl (w/v), 15 min extraction time and stirring speed at 600 rpm for DI-SDME; 3.5-µL C₂H₂Cl₄ as the extraction solvent, 15% NaCl (w/v), 21 min extraction time and flowing rate at 0.8 mL min^?1 for CFME. Under the previous optimal conditions, the linear range, detection limit (S/N = 3) and precision (RSD, n = 6) were 5.0-5000 ng mL^?1, 1.5 ng mL^?1, 6.9% for DI-SDME, and 4.0–10000 ng mL^?1, 2.5 ng mL^?1, 4.6% for CFME, respectively. Lake and river water samples were successfully analysed by DI-SDME and CFME. The result demonstrated that both SDME and CFME techniques are simple, low cost and amity to environment. As a result, the two approaches have tremendous potential in trace analysis of methomyl in natural waters.     

Antibiotic-assisted three-phase liquid-phase microextraction of aromatic amines from aqueous solutions combined with high-performance liquid chromatography

Three-phase liquid-phase microextraction (LLLME) combined with high-performance liquid chromatography (HPLC) equipped with a monolithic column for the analysis of some aromatic amines is described. These compounds were extracted from an aqueous sample (4.0 mL) adjusted to pH 13 with NaOH-NaCl solution (Donor Phase, P₁) into an organic phase (P₂, 150 μL of Benzyl alcohol and ethyl acetate mixture, 2:1) and then back-extracted into a microdrop of aqueous acceptor phase (P3) adjusted to pH 2 with Na₂HPO₄-H₃PO₄ buffer solution. The extraction time T1 (from P₁ to P₂) was 20 min, and T₂ (from P₂ to P₃) was 1 min. Different antibiotics as complexing agents for amines were added to the acceptor phase to improve the extraction time. Factors such as organic solvents, extraction times, addition of antibiotics to the acceptor phase, and stirring rate were optimized. The method was applied to the determination of aromatic amines in waste-water samples. Enrichment factors ranged from 189.0 to 395.5. The linearity range was from 2.5 to 1000 ng/mL, and the detection limits varied from 0.5 to 1.50 ng/mL. Relative standard deviations (%, n = 5) were found (at S/N 3) to be in the range of 1.3–8.5. All experiments were carried out at room temperature, 22 ± 0.5°C. The text was submitted by the authors in English.     

Preconcentration Ultra Trace of Cd(II) in Water Samples Using Dispersive Liquid‐Liquid Microextraction with Salen(N,N′‐Bis(Salicylidene)‐Ethylenediamine) and Determination Graphite Furnace Atomic Absorption Spectrometry

Dispersive liquid–liquid microextraction (DLLME) technique was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GF AAS). In this extraction method, 500 μL methanol (disperser solvent) containing 34 μL carbon tetrachloride (extraction solvent) and 0.00010 g Salen(N,N′‐bis(salicylidene)ethylenediamine) (chelating agent) was rapidly injected by syringe into the water sample containing cadmium ions (interest analyte). Thereby, a cloudy solution formed. The cloudy state resulted from the formation of fine droplets of carbon tetrachloride, which have been dispersed, in bulk aqueous sample. At this stage, cadmium reacts with Salen(N,N′‐bis(salicylidene)‐ethylenediamine), and therefore, hydrophobic complex forms which is extracted into the fine droplets of carbon tetrachloride. After centrifugation (2 min at 5000 rpm), these droplets were sedimented at the bottom of the conical test tube (25 ± 1 μL). Then a 20 μL of sedimented phase containing enriched analyte was determined by GF AAS. Some effective parameters on extraction and complex formation, such as extraction and disperser solvent type and their volume, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor 122 was obtained from only 5.00 mL of water sample. The calibration graph was linear in the range of 2‐21 ng L^?1 with a detection limit of 0.5 ng L^?1. The relative standard deviation (R.S.D._s) for ten replicate measurements of 20 ng L^?1 of cadmium was 2.9%. The relative recoveries of cadmium in tap, sea and rain water samples at a spiking level of 5 and 10 ng L^?1 are 99, 94, 97 and 96%, respectively. The characteristics of the proposed method have been compared with cloud point extraction (CPE), on‐line liquid‐liquid extraction, single drop microextraction (SDME), on‐line solid phase extraction (SPE) and co‐precipitation based on bibliographic data. Therefore, DLLME combined with GF AAS is a very simple, rapid and sensitive method, which requires low volume of sample (5.00 mL).     

Silver nanoparticles‐tragacanth gel as a green membrane for effective extraction and determination of capecitabine

A novel eco‐friendly and effective electromembrane extraction method combining high‐performance liquid chromatography with UV detection was developed for the enrichment and determination of capecitabine. Tragacanth‐silver nanoparticles conjugated gel was prepared by dissolving the tragacanth powder in synthesized silver nanoparticles solution and was used as a green membrane in electromembrane extraction. The porosity and presence of silver nanoparticles in the gel were characterized by field emission scanning electron microscopy. This new electromembrane extraction approach uses neither organic solvent nor carrier agents to extract the target analyte. The best electromembrane extraction efficiency was obtained by using 4.0 mm membrane gel thickness containing 2.5% w/v of tragacanth gum, donor phase pH = 5.0, acceptor phase pH = 3.0, applied voltage 50 V, extraction time 20 min, and agitation rate 500 rpm. During method validation under the optimized conditions, good linearity dynamic range between 1 and 500 ng/mL with the coefficient of determination (R²) = 0.998 was obtained. Limit of detection and Limit of quantitation were estimated to be 0.84 and 1.0 ng/mL, respectively. Finally, the applicability of this method in real samples was confirmed by an acceptable performance in extraction and determination of capecitabine in human plasma samples.     

Comparison of air‐agitated liquid–liquid microextraction and ultrasound‐assisted emulsification microextraction for polycyclic aromatic hydrocarbons determination in hookah water

In this work, two disperser‐free microextraction methods, namely, air‐agitated liquid–liquid microextraction and ultrasound‐assisted emulsification microextraction are compared for the determination of a number of polycyclic aromatic hydrocarbons in aqueous samples, followed by gas chromatography with flame ionization detection. The effects of various experimental parameters upon the extraction efficiencies of both methods are investigated. Under the optimal conditions, the enrichment factors and limits of detection were found to be in the ranges of 327–773 and 0.015–0.05 ng/mL for air‐agitated liquid–liquid microextraction and 406–670 and 0.015–0.05 ng/mL for ultrasound‐assisted emulsification microextraction, respectively. The linear dynamic ranges and extraction recoveries were obtained to be in the range of 0.05–120 ng/mL (R² ≥ 0.995) and 33–77% for air‐agitated liquid–liquid microextraction and 0.05–110 ng/mL (R² ≥ 0.994) and 41–67% for ultrasound‐assisted emulsification microextraction, respectively. To investigate this common view among some people that smoking hookah is healthy due to the passage of smoke through the hookah water, samples of both the hookah water and hookah smoke were analyzed.     

Application of ionic‐liquid‐supported magnetic dispersive solid‐phase microextraction for the determination of acaricides in fruit juice samples

In this study, ionic liquid (IL) supported magnetic dispersive solid‐phase microextraction was developed and a systematic investigation was conducted on imidazolium ILs for their extraction performance. This nano‐based pretreatment procedure was then applied for the determination of acaricides in fruit juice samples for the first time. A feature of this technique is that the commonly laborious chemical modification of magnetic nanoparticles (MNPs) was skillfully circumvented. Because of the combination of ILs, dispersive liquid–liquid microextraction, and dispersive MNP solid‐phase microextraction, the extraction efficiency can be significantly improved using commercial MNPs. Parameters of the extraction method were investigated by one‐factor‐at‐a‐time approach. The optimal experimental conditions were as follows: emulsification for 2 min by sonication with the addition of 50 μL [C₆MIM][NTf₂] in the dispersive liquid–liquid microextraction step and vortexing for 90 s after adding 40 mg spherical barium ferrite nanoparticles (20 nm). The desorption time was 2 min. Good linearity (0.5–500 ng/mL) and detection limits within the range of 0.05–0.53 ng/mL were achieved. The application of the proposed method was demonstrated by the analysis of real fruit juice samples, in which recoveries between 85.1 and 99.6% were obtained.     

Development of dispersive liquid-phase microextraction based on new ionic liquid 1,3-diisooctylimidazolium hexafluorophosphate as solvent for the extraction and determination of dicofol and its degradation products in water samples

In the current paper we describe a novel sample preparation technique termed dispersive liquid-phase microextraction for the preconcentration and determination of 2,2,2-trichloro-1,1-bis(4-chlorophenyl)ethanol (dicofol) and its degradation products in water samples that includes 2-(2-chlorophenyl)-2-(4-chlorophenyl)-1,1-dichloroethene(2,4′-DDE), 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane(4,4′-DDE) and 1,1,1-trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane (2,4′-DDT) coupled with gas chromatography mass spectrometry (GC-MS), in which a new ionic liquid 1,3-diisooctylimidazolium hexafluorophosphate abbreviated as [D(i-C₈)IM][PF₆] was used as extraction solvent. For each one extraction, 1.00 mL of the methanol solution containing 40 µL of the ionic liquid was sprayed into 25.00 mL of water sample. In the meantime the ionic liquid was finely dispersed into the aqueous phase and analytes were rapidly migrated into the ionic liquid. After the solution was centrifuged for 2 min at 5000 rpm, the droplets of the ionic liquid are subsided in the bottom of the conical test tube (30.0 ± 0.2 µL). Moreover, the factors relevant to extraction efficiencies were investigated and optimised including the volume of the ionic liquid, disperser solvent, extraction time, sample pH and ionic strength. Under optimal conditions, the enrichment factors of the extraction were between 550 and 725 with an extraction efficiency ranging from 66% to 87% for each different analyte. Finally, 1.0 µL of the ionic liquid collected from above extraction was injected into the injector block of GC-MS instrument for analysis. The detection limit (S/N = 3), the relative standard deviations for 2.0 µg L^?1 of the standard analyte (n = 5) and linearity in a calibration range were found to be 3–8 ng L^?1, 1.0–2.7% and 10–3000 ng L^?1, respectively. Good spiked recoveries over the range of 92.0–13.5% were obtained. The proposed method offers the advantages of simplicity of operation, rapidity, good extraction efficiency and enrichment factor; it has been successfully applied to determination of dicofol and its degradation products in environmental water samples.     

Polyethylene glycol grafted flower‐like cupric nano oxide for the hollow‐fiber solid‐phase microextraction of hexaconazole,penconazole, and diniconazole in vegetable samples

A simple, rapid, highly efficient, and reliable sample preparation method has been developed for the extraction and analysis of triazole pesticides from cucumber, lettuce, bell pepper, cabbage, and tomato samples. This new sorbent in the hollow‐fiber solid‐phase microextraction method is based on the synthesis of polyethylene glycol‐polyethylene glycol grafted flower‐like cupric oxide nanoparticles using sol–gel technology. Afterward, the analytes were analyzed by high‐performance liquid chromatography with ultraviolet detection. The main parameters that affect microextraction efficiency were evaluated and optimized. This method has afforded good linearity ranges (0.5–50 000 ng/mL for hexaconazol, 0.012–50 000 ng/mL for penconazol, and 0.02–50 000 ng/mL for diniconazol), adequate precision (2.9–6.17%, n = 3), batch‐to‐batch reproducibility (4.33–8.12%), and low instrumental LODs between 0.003 and 0.097 ng/mL (n = 8). Recoveries and enrichment factors were 85.46–97.47 and 751–1312%, respectively.     

LC Determination of 4-Bromoaniline in Green Algae Chlamydomonas reinhardtii After Continuous-Flow Microextraction

In this study, the determination of 4-Bromoaniline (4-BA) in green algae Chlamydomonas reinhardtii (C. reinhardtii) was investigated by applying continuous-flow microextraction (CFME) combined with high-performance liquid chromatography (HPLC). Continuous-flow microextraction was conducted in a homemade glass chamber, i.e. the sample solution flowed through a constant volume drop of solvent in the chamber at a constant flow rate. The effects of different factors on extraction efficiencies were also investigated and these factors included the kind of extraction solvent, solvent drop volume, sample flow rate, extraction time and addition amount of salt. Under the optimum extraction conditions (extraction solvent, carbon tetrachloride; solvent drop volume, 3.5 μL; sample flow rate, 1.0 mL min⁻¹; extraction time, 10 min; no addition of salt), the calibration plot was set up by plotting peak area against a series of 4-Bromoaniline concentrations (0.01–10 μg mL⁻¹) in aqueous solution. The correlation coefficient (r) was 0.9990. The limit of detection (LOD) was 0.6 ng mL⁻¹. The precision of this method was obtained by successive five time analyses of 100-ng mL⁻¹ standard solution of 4-Bromoaniline, and the relative standard deviation (RSD) was 3.5%. The concentration factor was calculated by the ratio of peak area of the analyte obtained after and before extraction and found to be 10.6. 4-Bromoaniline residues in Chlamydomonas. reinhardtii cells and tap water samples were satisfactorily analyzed according to the method described above.     

Determination of Ultra-Trace Cobalt in Water Samples Using Dispersive Liquid-Liquid Microextraction Followed by Graphite Furnace Atomic Absorption Spectrometry

A novel method for the determination of ultra-trace cobalt by dispersive liquid–liquid microextraction (DLLME) coupled with graphite furnace atomic absorption spectrometry has been developed. It is based on the color reaction of Co²⁺ with 2-(5-bromo-2-pyridylazo)-5-dimethylaminoaniline (5-Br-PADMA) in a Britton–Robinson buffer solution at pH 6.0 to form stable hydrophobic chelates, which were separated and enriched by DLLME with 1,2-dichloroethane (CH₂ClCH₂Cl) as extraction and acetonitrile (CH₃CN) as a dispersive solvent. The sedimented phase containing the chelates is then determined with GFAAS. Parameters that affect extraction efficiency, such as types and volumes of extraction and disperser solvents, pH of sample solution, extraction time, concentration of the chelating agent 5-Br-PADMA, and salt effect, were investigated. Under optimal conditions, the calibration graph was linear over the range 0.05–1.0 ng/mL, with a correlation coefficient of 0.9922 and a detection limit of 0.03 ng/mL. Preconcentration factor (PF) is calculated as the ratio of the aqueous solution volume (5 mL) to that of the organic phase volume (40 μL), and enrichment factor (EF) is calculated as the ratio of the slopes of the calibration graphs obtained with and without DLLME for 5.0 mL of sample solution, which were 120 and 112.5, respectively. The extraction efficiency, calculated by EF/PF·100, was 93.8%. The relative standard deviation (RSD) at the 0.5 ng/mL Co²⁺ level was 3.8% (n = 6). The method has been applied to the determination of trace cobalt in water samples with satisfactory results.     

Simple and rapid determination of phthalates using microextraction by packed sorbent and gas chromatography with mass spectrometry quantification in cold drink and cosmetic samples

A simple and rapid method using microextraction by packed sorbent coupled with gas chromatography and mass spectrometry has been developed for the analysis of five phthalates, namely, diethyl phthalate, benzyl‐n‐butyl phthalate, dicyclohexyl phthalate, di‐n‐butyl phthalate, and di‐n‐propyl phthalate, in cold drink and cosmetic samples. The various parameters that influence the microextraction by packed sorbent performance such as extraction cycle (extract–discard), type and amount of solvent, washing solvent, and pH have been studied. The optimal conditions of microextraction using C₁₈ as the packed sorbent were 15 extraction cycles with water as washing solvent and 3 × 10 μL of ethyl acetate as the eluting solvent. Chromatographic separation was also optimized for injection temperature, flow rate, ion source, interface temperature, column temperature gradient and mass spectrometry was evaluated using the scan and selected ion monitoring data acquisition mode. Satisfactory results were obtained in terms of linearity with R² >0.9992 within the established concentration range. The limit of detection was 0.003–0.015 ng/mL, and the limit of quantification was 0.009–0.049 ng/mL. The recoveries were in the range of 92.35–98.90% for cold drink, 88.23–169.20% for perfume, and 88.90–184.40% for cream. Analysis by microextraction by packed sorbent promises to be a rapid method for the determination of these phthalates in cold drink and cosmetic samples, reducing the amount of sample, solvent, time and cost.     

Study of enrichment factors for six β‐blockers in aliphatic alcohols by hollow‐fiber liquid‐phase microextraction

The selectivity of a suitable organic solvent is key for extraction in liquid‐phase microextraction experiments. Nevertheless, the screening process remains a daunting task. Our research aimed to study the relationship between extraction efficiency and extraction solvents, analytes, and finally select the appropriate extraction solvent. In the present article, β‐blockers and six extraction solvents were chosen as the models and hollow‐fiber liquid‐phase microextraction was conducted. The relationship was built by statistical analysis on the data. Factors affecting extraction efficiency including the logarithms of the octanol/water partition coefficient (logP_o/w) of analytes, acid dissociation constants, the logarithms of the octanol/water partition coefficient of solvents and pH of the sample solution were investigated. The results showed that a low water solubility of extraction solvent is the foundation to ensure higher extraction efficiency. Moreover, when ΔlogP_o/w > 0, a higher extraction efficiency is observed at lower ΔlogP_o/w, on the contrary, when ΔlogP_o/w < 0, extraction efficiency is higher as the absolute value of ΔlogP_o/w becomes greater. Finally, the relationship between enrichment factor and extraction solvents, analytes was established and a helpful guidance was provided for the selection of an optimal solvent to obtain the best extraction efficiency by liquid‐phase microextraction.     

Detection of organophosphate pesticides in human body fluids by headspace solid-phase microextraction (SPME) and capillary gas chromatography with nitrogen-phosphorus detection

Summary Organosphosphate pesticides have been found extractable by headspace solid-phase microextraction (SPME), and the best conditions of their extraction from human whole blood and urine samples have been investigated. The body fluid samples containing nine pesticides (IBP, methyl parathion, fenitrothion, malathion, fenthion, isoxathion, ethion, EPN and phosalone) were heated at 100°C in a septum-capped vial in the presence of various combinations of acid and salts, and SPME fiber was exposed to the headspace of the vial to allow adsorption of the pesticides before capillary gas chromatography (GC) with nitrogen-phosphorus detection. The heating with distilled water/HCl/(NH₄)₂SO₄/NaCl and with distilled water/HCl gave the best results for urine and whole blood, respectively. Recoveries of the nine pesticides were 0.8–10.6% except for phosalone (0.03%) for whole blood, and 3.8–40.2% for urine. The calibration curves for the pesticides showed linearity in the range of 50–400 ng/0.5 mL for whole blood except for malathion (100–400 ng/0.5 mL whole blood) and 7.5–120 ng/0.5 mL for urine except for phosalone (15–120 ng/0.5 mL urine) with detection limits of 2.2–40 ng/0.5 mL for whole blood and 0.8–12 ng/0.5 mL for urine.     

Previously undescribed benzoxepins with bioactivities against inducible pro-inflammatory cyclooxygenase and lipoxygenase from Rhizophora annamalayana Kathir

Two unprecedented benzoxepins were obtained from the ethyl acetate fraction of the leaves of Rhizophora annamalayana Kathir, and characterized as 4-(11-(hydroxymethyl)-10-methylpentan-2-yl)-4, 5-dihydrobenzo[c]oxepin-1(3H)-one (1) and (E)-methyl-14-hydroxy-4-(11-(5-hydroxy-1-oxo-3,4,5-tetrahydrobenzo[c]oxepin-4-yl)ethyl)-10-methylhept-11-enoate (2). The benzoxepin 2 exhibited greater 1, 1-diphenyl-2-picrylhydrazyl and 2, 2′-azino-bis-3 ethylbenzothiozoline-6-sulfonic acid diammonium radical scavenging assays (IC₅₀ 0.68 and 0.84 mg/mL, respectively) than those recorded with 1 (IC₅₀ 0.70 and 0.89 mg/mL, respectively). The tetrahydrobenzo[c]oxepin analogue (2) exhibited significantly great cyclooxygenase-2 and 5-lipoxygenase inhibitory properties (IC₅₀ 0.87 and 0.94 mg/mL, respectively), while compared with its dihydrobenzo[c]oxepin-1(3H)-one isoform (1) (IC₅₀ 1.16 and 1.64 mg/mL, respectively). The dihydrobenzo[c]oxepin-1(3H)-one isoform (2) exhibited significantly greater selectivity index (~2) than synthetic ibuprofen (0.44) (p < 0.05), which attributed the higher anti-inflammatory selectivity of the former against inducible pro-inflammatory cyclooxygenase-2 than its constitutive isoform (cyclooxygenase-1). No significant difference in 5-lipoxygenase (5-LOX) inhibitory activities were apparent between compound 2 (IC₅₀ 0.94 mg/mL) and synthetic ibuprofen (IC₅₀ 0.93 mg/mL).     

Ionic‐liquid‐mediated poly(dimethylsiloxane)‐ grafted carbon nanotube fiber prepared by the sol–gel technique for the head space solid‐phase microextraction of methyl tert‐butyl ether using GC

A headspace solid‐phase microextraction method was developed for the preconcentration and extraction of methyl tert‐butyl ether. An ionic‐liquid‐mediated multiwalled carbon nanotube–poly(dimethylsiloxane) hybrid coating, which was prepared by covalent functionalization of multiwalled carbon nanotubes with hydroxyl‐terminated poly(dimethylsiloxane) using the sol–gel technique, was used as solid‐phase microextraction adsorbent. This innovative fiber exhibited a highly porous surface structure, high thermal stability (at least 320°C) and long lifespan (over 210 uses). Potential factors affecting the extraction efficiency were optimized. Under the optimum conditions, the method LOD (S/N = 3) was 0.007 ng/mL and the LOQ (S/N = 10) was 0.03 ng/mL. The calibration curve was linear in the range of 0.03–200 ng/mL. The RSDs for one fiber (repeatability, n = 5) at three different concentrations (0.05, 1, and 150 ng/mL) were 5.1, 4.2, and 4.6% and for the fibers obtained from different batches (reproducibility, n = 3) were 6.5, 5.9, and 6.3%, respectively. The developed method was successfully applied to the determination of methyl tert‐butyl ether in different real water samples on three consecutive days. The relative recoveries for the spiked samples with 0.05, 1, and 150 ng/mL were between 94–104%.     

Hollow-Fiber-Based LPME as a Reliable Sampling Method for Gas-Chromatographic Determination of Pharmacokinetic Parameters of Valproic Acid in Rat Plasma

A sensitive and simple method based on two-phase liquid-phase microextraction in porous hollow fiber followed by gas chromatography-flame ionization detection was developed for quantification and pharmacokinetic study of valproic acid (VPA, an antiepileptic drug) in rat plasma after oral administration of pure sodium valproate (25 mg kg⁻¹). Some parameters such as type of organic solvent, pH of sample solution, stirring speed, salt addition, extraction time, and volume of sample that affected extraction efficiency of VPA were optimized. Under optimized microextraction conditions, VPA was extracted with 10 μL 1-octanol from 0.5 mL rat plasma previously diluted with 4.5 mL acidified and salinated water (pH 2) using 1-octanoic acid as internal standard. The limit of detection was 17 ng mL⁻¹ with linear response over the concentration range of 50–10,000 ng mL⁻¹ with correlation coefficient higher than 0.998. The developed method was successfully applied to determination of pharmacokinetic parameters such as t _max (peak time in concentration–time profile), C _max (peak concentration in concentration–time profile), t _1/2 (elimination half-life), AUC_0–t (area under the curve for concentration versus time), clearance, and apparent distribution volume in rats following oral administration of VPA.

     

Ultrasound‐assisted temperature‐controlled ionic liquid emulsification microextraction coupled with capillary electrophoresis for the determination of parabens in personal care products

We developed a CE and ultrasound‐assisted temperature‐controlled ionic liquid emulsification microextraction method for the determination of four parabens (methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) in personal care products including mouthwash and toning lotion. In the proposed extraction procedure, ionic liquid (IL, 1‐octyl‐3‐methylimidazolium hexafluorophosphate) was used as extraction solvent, moreover, no disperser solvent was needed. Parameters affecting the extraction efficiency including volume of IL, heating temperature, ultrasonic time, extraction time, sample pH, ionic strength, and centrifugation time were optimized. Under the optimized conditions, the method was found to be linear over the range of 3–500 ng/mL with coefficient of determination (R²) in the range of 0.9990–0.9998. The LODs and LOQs for the four parabens were 0.45–0.72 ng/mL and 1.50–2.40 ng/mL, respectively. Intraday and interday precisions (RSDs, n = 5) were in the range of 5.4–6.8% and 7.0–8.7%, respectively. The recoveries of parabens at different spiked levels ranged from 71.9 to 119.2% with RSDs less than 9.5%.