Optimization of temperature-controlled ionic liquid dispersive liquid phase microextraction combined with high performance liquid chromatography for analysis of chlorobenzenes in water samples

Temperature-controlled ionic liquid dispersive liquid phase microextraction (TCIL-DLPME) combined with high performance liquid chromatography-diode array detection (HPLC-DAD) was applied for preconcentration and determination of chlorobenzenes in well water samples. The proposed method used 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mim][PF₆]) as the extraction solvent. The effect of different variables on extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the TCIL-DLPME were extraction solvent volume, salt effect, solution temperature, extraction time, centrifugation time, and heating time. The Plackett-Burman design was employed for screening to determine the variables significantly affecting the extraction efficiency. Then, the significant factors were optimized by using a central composite design (CCD) and the response surface equations were developed. The optimal experimental conditions obtained from this statistical evaluation included: extraction solvent volume, 75 μL; extraction time, 20 min; centrifugation time, 25 min; heating time, 4 min; solution temperature, 50 °C; and no addition of salt. Under optimal conditions, the preconcentration factors were between 187 and 298. The limit of detections (LODs) ranged from 0.05 μg L⁻¹ (for 1,2-dichlorobenzene) to 0.1 μg L⁻¹ (for 1,2,3-trichlorobenzene). Linear dynamic ranges (LDRs) of 0.5-300 and 0.5-500 μg L⁻¹ were obtained for dichloro- and trichlorobenzenes, respectively. The performance of the method was evaluated for extraction and determination of chlorobenzenes in well water samples in micrograms per liter and satisfactory results were obtained (RSDs < 9.2%).     

Effects of different parameters on supercritical fluid extraction of steroid drugs, from spiked matrices and tablets

Feasibility of supercritical CO(2) extractions of two steroid drugs, medroxyprogesterone acetate (med) and cyproterone acetate (cyp), were evaluated. The effects of temperature (308-348 K), pressure (100-300 bar), static extraction time (5-15 min), dynamic extraction time (10-30 min) and percent methanol modifier (1-10% v/v) on the SFE recoveries of these drugs from spiked matrices (glass) and pharmaceutical dosages (tablets) were investigated. The results showed that minor structural differences between related compounds might lead to dramatically differences in extraction behaviors under the same conditions. The optimum SFE conditions to extract the drugs from spiked glass were 10 min static, 30 min dynamic, 300 bar, 348 K and 5% modifier in the case of med acetate and 10 min static, 30 min dynamic, 100 bar, 308 K, and 10% modifier in the case of cyp. Under these conditions above 90% of the total recovery was obtained for both drugs. Extractions from pharmaceutical dosages were less efficient compared to glass beads under the same conditions. Quantitative recovery of solutes from tablets were obtained upon changing extraction conditions to: 15 min static, 45 min dynamic, P=300 bar, 20% modifier (for med) and 10% (for cyp).     

Tandem air-agitated liquid–liquid microextraction as an efficient method for determination of acidic drugs in complicated matrices

A rapid and simple microextraction method with a high sample clean-up, termed as tandem air-agitated liquid–liquid microextraction (TAALLME), is described. This method is based upon the tandem implementation of the air-agitated liquid–liquid microextraction (AALLME), and this approach improves the applicability of the dispersive liquid–liquid microextraction (DLLME) methods in complicated matrices. With very simple tools, the three non-steroidal anti-inflammatory drugs diclofenac, ibuprofen, and mefenamic acid were efficiently extracted, with an overall extraction time of 7 min. By performing the first AALLME, these acidic analytes, contained in an aqueous sample solution (donor phase, 8.0 mL), were extracted into the organic solvent (1,2-dichloroethane, 37 μL), and their simple back-extraction into the aqueous acceptor solution (pH, 10.01, 51 μL) was obtained in 2 min by a second implementation of AALLME. Response surface methodology (RSM) was used for optimization of the experimental parameters. The pH values 2.94 and 10.01 were obtained for the donor and acceptor phases, respectively, and the volumes 99.5 and 51 μL were obtained for the organic solvent and the acceptor phase, respectively, as the optimal extraction conditions. Under the optimized conditions, tandem AALLME-HPLC-UV provided a good linearity in the range of 0.5–4000 ng mL⁻¹, limits of detection (0.1–0.3 ng mL⁻¹), extraction repeatabilities (relative standard deviations (RSDs) below 7.7%, n = 5), and the enrichment factors (EFs) of 80–104. Finally, the applicability of the proposed method was evaluated by the extraction and determination of the drugs under study in the wastewater and human plasma samples.     

Structural investigation of aluminium doped ZnO nanoparticles by solid-state NMR spectroscopy

The electrical conductivity of aluminium doped zinc oxide (AZO, ZnO:Al) materials depends on doping induced defects and grain structure. This study aims at relating macroscopic electrical conductivity of AZO nanoparticles with their atomic structure, which is non-trivial because the derived materials are heavily disordered and heterogeneous in nature. For this purpose we synthesized AZO nanoparticles with different doping levels and narrow size distribution by a microwave assisted polyol method followed by drying and a reductive treatment with forming gas. From these particles electrically conductive, optically transparent films were obtained by spin-coating. Characterization involved energy-dispersive X-ray analysis, wet chemical analysis, X-ray diffraction, electron microscopy and dynamic light scattering, which provided a basis for a detailed structural solid-state NMR study. A multinuclear ((27)Al, (13)C, (1)H) spectroscopic investigation required a number of 1D MAS NMR and 2D MAS NMR techniques (T(1)-measurements, (27)Al-MQMAS, (27)Al-(1)H 2D-PRESTO-III heteronuclear correlation spectroscopy), which were corroborated by quantum chemical calculations with an embedded cluster method (EEIM) at the DFT level. From the combined data we conclude that only a small part of the provided Al is incorporated into the ZnO structure by substitution of Zn. The related (27)Al NMR signal undergoes a Knight shift when the material is subjected to a reductive treatment with forming gas. At higher (formal) doping levels Al forms insulating (Al, H and C containing) side-phases, which cover the surface of the ZnO:Al particles and increase the sheet resistivity of spin-coated material. Moreover, calculated (27)Al quadrupole coupling constants serve as a spectroscopic fingerprint by which previously suggested point-defects can be identified and in their great majority be ruled out.     

Synthesis and characterization of 1,3,5-tris((1/2<Emphasis Type="Italic">H</Emphasis>-tetrazol-5-yl)methyl)-1,3,5-triazinane-2,4,6-trione

2,2′,2″-(2,4,6-Trioxo-1,3,5-triazinane-1,3,5-triyl) triacetonitrile (or tris-(cyanomethyl)-isocyanurate) and 1,3,5-tris((1/2H-tetrazol-5-yl)methyl)-1,3,5-triazinane-2,4,6-trione (or tris-(5-tetrazolylmethyl)-isocyanurate) were synthesized with new methods. High yields, simple methodology, and cheapness are advantages of the methods. Furthermore, 1,3,5-tris((1/2H-tetrazol-5-yl)methyl)-1,3,5-triazinane-2,4,6-trione was synthesized in the less hazardous condition. The compounds were characterized by elemental analysis, IR, ¹HNMR, ¹³CNMR and mass spectroscopic analysis. In addition, DSC/TGA measurements were carried out to determine the thermal behavior of the final product.     

Liquid-phase microextraction based on solidified floating drops of organic solvents

Microextraction of organic or inorganic analytes using solidified floating drops of organic solvents is a fairly new method that is simple and rapid, and requires only small quantities of solvents and reagents. This review (with 109 references) covers published work up to Sep. 2012, and describes how the method was combined with analytical techniques such as GC, HPLC, ICP-OES and electrothermal atomic absorption spectrometry. We discuss basic principles and the main parameters that affect the extraction efficiency, and give specific applications of the technique.

Homogeneous liquid‐phase microextraction followed by filtration‐based phase separation coupled to high‐performance liquid chromatography

A simple homogenous liquid‐phase microextraction methodology applying octanoic acid as the extraction phase was introduced for determination of chlorobenzenes. In this approach, phase separation phenomenon occurred by changing pH of the solution. The extraction phase was isolated based on filtration of emulsion instead of centrifugation and it was introduced to the high‐performance liquid chromatography instrument as an on‐line procedure. This method was used for extraction and determination of five chlorobenzenes in different samples. Experimental design and response surface methodology were used for the optimization of various parameters influencing the extraction efficiency of the method. Under optimal conditions, chlorobenzenes were effectively extracted, and preconcentration factors of 255–294 were obtained. The calibration curves were investigated in the concentration range of 1–200 μg/L and good linearity was achieved with coefficient of determinations better than 0.997. Limits of detection of 0.1 and 0.3 μg/L and suitable precision with relative standard deviations better than 5.1% (n = 5) were attained. Finally, the proposed method was applied to determine the concentration of chlorobenzenes in different samples and acceptable recoveries were gained.     

Study of thermal analysis and kinetic decomposition of polybutadiene acrylonitrile acrylic acid (PBAN)

Journal of Thermal Analysis and Calorimetry - This paper describes thermochemical properties and decomposition characteristics of polybutadiene acrylonitrile acrylic acid (PBAN). The thermal...     

Improving catalytic converter performance by controlling the structural and redox properties of Zr-doped CeO2 nanorods supported Pd catalysts

Research on Chemical Intermediates - The work herein introduces a facile and novel synthesis procedure for producing Zr-doped CeO2 nanorod catalysts applicable for upgrading the car catalytic...