Rapid and simple determination of gabapentin in urine by ion mobility spectrometry.

Gabapentin is a pharmacological agent used in the treatment of epileptic seizures. In this work, a fast method is proposed for determination of gabapentin in urine by ion mobility spectrometry (IMS) without any extraction and derivatization. ZnCl2 was used as an effective protein precipitating reagent to remove the urine proteins. It was found that urea content of urine interferes with detection of gabapentin by IMS. By applying a delay on the carrier gas flow after injection of the sample, we could solve the urea interference to achieve gabapentin signal recovery of ∼70% in urine relative to that in water.

Flax Biomass Conversion via Controlled Oxidation: Facile Tuning of Physicochemical Properties.

The role of chemical modification of pristine linen fiber (LF) on its physicochemical and adsorption properties is reported in this contribution. The surface and textural properties of the pristine LF and its peroxyacetic acid- (PAF) and chlorite-treated (CF) fiber forms were characterized by several complementary methods: spectroscopy (SEM, TEM, FT-IR, and XPS), thermal analysis (DSC and TGA), gas/water adsorption isotherms, and zeta potential (ξ). The results obtained reveal that the surface charge and textural properties (surface area and pore structure) of the LF material was modified upon chemical treatment, as indicated by changes in the biomass composition, morphology, ξ-values, and water/dye uptake properties of the fiber samples. Particularly, the pristine LF sample displays preferential removal efficiency (ER) of methylene blue (MB) dye with ER ~3-fold greater (ER~62%) as compared to the modified materials (CF or PAF; ER~21%), due to the role of surface charge of pectins and lignins present in pristine LF. At higher MB concentration, the relative ER values for LF (~19%) relative to CF or PAF (~16%) reveal the greater role of micropore adsorption sites due to the contributing effect of the textural porosity observed for the modified flax biomass at these conditions. Similar trends occur for the adsorption of water in the liquid vs. vapour phases. The chemical treatment of LF alters the polarity/charge of the surface functional groups, and pore structure properties of the chemically treated fibers, according to the variable hydration properties. The surface and textural properties of LF are altered upon chemical modification, according to the variable adsorption properties with liquid water (l) vs. water vapor (g) due to the role of surface- vs. pore-sites. This study contributes to an understanding of the structure-adsorption properties for pristine and oxidized flax fiber biomass. The chemical conversion of such biomass yields biomaterials with tunable surface and textural properties, as evidenced by the unique adsorption properties observed for pristine LF and its modified forms (CF and PAF). This study addresses knowledge gaps in the field by contributing insight on the relationship between structure and adsorption properties of such LF biomass in its pristine and chemically modified forms.

A Non-linear Viscoelastic Model of the Incudostapedial Joint.

The ossicular joints of the middle ear can significantly affect middle-ear function, particularly under conditions such as high-intensity sound pressures or high quasi-static pressures. Experimental investigations of the mechanical behaviour of the human incudostapedial joint have shown strong non-linearity and asymmetry in tension and compression tests, but some previous finite-element models of the joint have had difficulty replicating such behaviour. In this paper, we present a finite-element model of the joint that can match the asymmetry and non-linearity well without using different model structures or parameters in tension and compression. The model includes some of the detailed structures of the joint seen in histological sections. The material properties are found from the literature when available, but some parameters are calculated by fitting the model to experimental data from tension, compression and relaxation tests. The model can predict the hysteresis loops of loading and unloading curves. A sensitivity analysis for various parameters shows that the geometrical parameters have substantial effects on the joint mechanical behaviour. While the joint capsule affects the tension curve more, the cartilage layers affect the compression curve more.

Characterization and performance evaluation of functional monomer effect on molecular imprinted polyurethane foam.

Herein we describe a methodology to synthesis polyurethane foam molecularly imprinted polymer (PUF-MIP) by using functional monomer for selective extraction of alprazolam. For this purpose, the various percentages of functional monomer are used to synthesis PUF-MIP of alprazolam. To evaluate the selectivity of synthesized PUF-MIP HPLC analysis is applied by introducing caffeine and methadone as an interference. To optimize the proposed technique, effective parameters in the SPE procedure including pH, flow, and salt present is investigated by experimental design. Finally, this method is evaluated in urine sample to monitor alprazolam dosage. In the optimized condition, the synthesized polymer indicates high selectivity value about 71% for alprazolam and 96.8% recovery for MIPUF compared with non-imprinted polyurethane foam (NIPUF). The linear dynamic range (LDR) of 0.03-60 mg L-1, the limit of detection of 8-10 µg L-1, the relative standard deviation (RSD, n = 3) of 2.88-3.65 % and quantification of 25-30 µg L-1 is obtained for HPLC analysis based on PUF-MIP extraction.

Evaluation of an Experimentally Designed Molecular Imprinted Polyurethane Foam Performance for Extraction of Alprazolam.

Industrial polyurethane rigid foam (PUF) was selected as a substrate for selective solid phase extraction of Alprazolam. Effective parameters for raising selectivity of the PUF were evaluated. Synthetic molecularly imprinted polyurethane foam (MIPUF) was tracked as selective adsorbent and its characteristic was pondered by analytical methods. Optimization was done by central composite design (CCD) to have high efficiency of the polymer adsorption. Two different extraction methods were compared in the selective adsorption processes using MIPUF and NIPUF, batch system and continuous (cartridge) system. Results of the adsorption of alprazolam on the MIPUF had 39% more recovery than NIPUF (reference polymer). Then, the proposed method suggests a selective extraction of mentioned analyte from urine and tablets as complex matrixes.

Fabrication of a nanomaterial-based fluorescence sensor constructed from ligand capped CdTe quantum dots for ultrasensitive and rapid detection of silver ions in aqueous samples.

In this study, CdTe QDs were prepared in aqueous medium and then capped with a synthetic heterocycle ligand (CdTe/L QDs) via surface modification method. Characterization of synthesized CdTe/L QDs was carried out through various analytical techniques including fluorescence spectroscopy, transmission electron microscopy (TEM), UV-Vis spectrophotometry, thermo-gravimetric (TG) analysis and Fourier transform infrared (FTIR). The fluorescence intensity of the CdTe/L QDs at 520 nm (excitation at 380 nm) was selectively quenched in the presence of trace amounts of silver ions. CdTe/L QDs were utilized as an ultrasensitive and selective fluorescent sensor for determination of trace concentrations of silver ions with a detection limit of 6.12 ±â€¯0.11 × 10-10 mol L-1 and a linear range of 2.04 ±â€¯0.10 × 10-9 mol L-1-3.63 ±â€¯0.12 × 10-7 mol L-1. The fabricated optical sensor was also used for the measurement of silver ions in real water samples which yielded satisfactory analytical results. These results were also evaluated with inductively coupled plasma emission spectroscopy (ICP-OES). This study shows that CdTe/L QDs could have potential applications in selective and sensitive analysis of different water samples for detection of silver ions.

Synergistic co-delivery of doxorubicin and melittin using functionalized magnetic nanoparticles for cancer treatment: loading and in vitro release study by LC-MS/MS.

In this study, citric acid-functionalized Fe3O4 magnetic nanoparticles (CA-MNPs) were prepared via a coprecipitation method and were fully characterized. Doxorubicin (DOX) and melittin (MEL), as anticancer agents, were loaded onto CA-MNPs surface through electrostatic interactions with the aim to achieve an effective co-delivery system for cancer therapy. The loading efficiency and in vitro release profiles of DOX and MEL were investigated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The MS/MS step was performed in the selected reaction monitoring (SRM) mode which enabled simultaneous quantification of the analytes with high specificity and sensitivity. An excellent loading efficiency of about 100% was achieved for DOX and MEL in a drug to nanocarrier ratio of 1:10. The in vitro release of the drugs from CA-MNPs was evaluated for 8 h at pH 7.4, 5.5 and 4.5. The experimental results revealed that the release behaviour of both of the anticancer agents was strongly pH-dependent and significantly enhanced at pH 4.5. The in vitro MTT assay on MCF-7 breast cancer cell line exhibited a synergistic effect between DOX and MEL which led to substantially greater antitumor efficacy, compared to single administration of these anticancer agents at equivalent doses. The results indicated that the co-delivery system of (DOX/MEL)-loaded CA-MNPs is highly capable to be used in magnetically targeted cancer therapy.

Ligand-Capped CdTe Quantum Dots as a Fluorescent Nanosensor for Detection of Copper Ions in Environmental Water Sample.

In this work, as a novel fluorescent nano-sensor, a ligand-capped CdTe QDs (CdTe-L QDs) was designed for the detection and quantification of Cu2+ ions in environmental water samples. The synthesized QDs were characterized by transmission electron microscopy (TEM), thermo-gravimetric (TG) analysis, Fourier transform infrared (FTIR), UV-Vis spectrophotometry and fluorescence spectroscopy. Optical properties of the produced nanosensor were monitored by UV-Vis and fluorescence spectrophotometry. It was observed that fluorescence intensity of the produced nano-sensor selectively quenched by adding Cu2+ ions in comparison to other metal ions tested. Using CdTe-L QDs, a rapid and facile analytical method was developed to determine Cu2+ ions in the concentration range of 5.16 ± 0.07 × 10- 8 mol L- 1-1.50 ± 0.03 × 10- 5 mol L- 1 with a detection limit of 1.55 ± 0.05 × 10- 8 mol L- 1. The nanosensor was successfully applied for the determination of Cu2+ ions in various water samples, and the results were compared with the standard method. Graphical Abstract.

Capillary Force between Flexible Filaments.

Liquid droplets bridging filaments are ubiquitous in nature and technology. Although the liquid-surface shape and the capillary force and torque have been studied extensively, the effect of filament flexibility is poorly understood. Here, we show that elastic deformation (at large values of the elasto-capillary number) can significantly affect the liquid-surface shape and capillary force. The equilibrium state of parallel filaments is calculated using analytical approximations and numerical solutions for the fluid interface. The results compare well, and the numerical solution is then applied to crossing filaments. In the investigated range of parameters, the capillary force increases rapidly when the filaments touch. The force decreases continuously when decreasing the liquid volume for parallel hydrophilic filaments but produces a maximum for crossed filaments. The liquid volume at the maximum force is reported when changing the filament flexibility, crossing angle, and contact angle. These results may be beneficial in applications where the strength and structure of wet fibrous materials are important, such as in paper formation and when welding flexible components.

Bubbles and drops on curved surfaces.

Surface curvature affects the shape, stability, and apparent contact angle of sessile and pendant drops. Here, we develop an approximate analytical solution for non-axisymmetric perturbations to small spherical drops on a flat substrate, assuming a fixed contact angle and fixed drop volume. The analytical model is validated using numerical solutions of the Laplace equation from the Surface Evolver software. We investigate the effects of surface curvature on drop shape, pressure, and surface energy, ascertaining the energy-gradient force that drives lateral drop migration. By balancing this force with the viscous resistance/drag force, in the lubrication approximation, we predict velocities of the order of 0.1 mm s(-1) for 1 mm diameter drops of water with a 30° contact angle on a substrate with a curvature gradient of 0.01 mm(-2), achieved, for example, on a harmonic surface with a wavelength of 4 cm and an amplitude of 4 mm.

Photoelectrocatalytic degradation of acid dye using Ni-TiO2 with the energy supplied by solar cell: mechanism and economical studies.

This paper reports an investigation into the effect of a number of operating factors on the removal of Acid Red 88 from an aqueous solution through photoelectrocatalysis: photocatalyst dose, dye concentration, pH, bias potential, and electrolyte concentration. The photocatalyst was Ni-TiO2 applied in suspension to the solution to achieve a larger catalyst surface area. The optimum values for photocatalyst dose, dye concentration, and electrolyte concentration turned out to be 0.6 mg L(-1), 50 mg L(-1), and 5 mg L(-1), respectively. Also, the best pH was found to be 7, and bias potential proved to be best at 1.6 V. The aqueous solution was characterized for its COD and TOC. Photocatalyst efficiency was evaluated using SEM and XRD techniques. The characterization of the post-treatment product using FT-IR, HPLC, and GC-MS studies revealed intermediate compounds. A pathway was proposed for the degradation of the dye. The energy required by the experiment was supplied by solar cells, meaning the money that would have otherwise been spent on electricity was saved. Cost analysis was also done for the treatment process.

A simple and high resolution ion-pair HPLC method for separation and simultaneous determination of nitrate and thiocyanate in different water samples.

An ion-pair reversed-phase high-performance liquid chromatography method with isocratic elution and ultraviolet detection was developed and validated for the separation and simultaneous determination of nitrate and thiocyanate. The separation was performed on a C18 analytical column with mobile phase containing 0.08 mM hexadecyltrimethylammonium bromide as an ion-pair reagent, 40 mM of acetate buffer and 30% methanol at pH 3.2. The detection was monitored at 206 nm. The response was linear from 1 to 10 mM for nitrate, with a detection limit of 0.05 mM, and 1 to 10 mM for thiocyanate, with a detection limit of 0.31 mM. Calibration curves were found to be linear in these concentration ranges with correlation coefficient better than 0.99.

Using a new ligand for solid phase extraction of mercury.

The octadecyl silica cartridge as a sorbent and 4-bp db (1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene) as a ligand is a simple, rapid and reliable method for extracting and preconcentrating of Hg(II) in real samples prior to cold vapor atomic absorption spectrometry. Sample solutions were passed through a column at pH 4.5 then retained mercury ions on the column were eluted with minimal amount of 0.01 M nitric acid with 3 mL min(-1) flow rate. The effect of pH, type of buffer, flow rate of sample and eluent, type and volume of the eluent were investigated and optimized. At optimum effective parameters, concentration factor and detection limit were achieved 128 and 1.87 ng L(-1), respectively.

DABTZ as a new reagent for solid phase extraction and spectrophotometric determination of trace amount of Hg(II) in water sample.

A novel sensitive and simple method for rapid and selective extraction, preconcentration and determination of mercury as its 2,2' diamino-4,4' bithiazole (DABTZ) complex by using octadecylsilica cartridges and spectrophotometry is presented. Extraction efficiency and the influence of flow rates of sample solution and eluent, pH, amount of DABTZ, type and least amount of eluent for elution of mercury complex from cartridges, break through volume and limit of detection were evaluated. Also the effects of various cationic and anionic interferences on percent recovery of mercury were studied. Average extraction efficiency > 90% was obtained by elution of the cartridge with minimal amount of solvent in the presence of interferences. A preconcentration factor of 152 and a detection limit of 10.92 ng mL(-1) were obtained. The method was applied to the recovery and determination of mercury in different water samples.