Pesticide residues in dates using a modified QuEChERS method and GC-MS/MS.

The aim of this study was to develop a convenient, fast, effective and safe analytical method (QuEChERS) to determine 198 pesticide residues in multi-source date palm fruits using gas chromatography-tandem mass spectrometry (GC-MS/MS). The calibration curves for most pesticides were linear in the range of 15-150 µg/kg, with r2 values higher than 0.9934 and the relative standard deviation for all pesticides was ≤20%. The mean recovery rate of pesticides was 70-120% and limits of detection (LODs) and limits of quantification (LOQs) were in the range of 5-14 µg/kg and 14-40 µg/kg, respectively. The validated procedure was used to monitor pesticide residues in 30 fresh date samples. It could be concluded that the modified QuEChERS extraction method was efficient in analysing pesticide residues in dates palm and none of the samples contained residues above the MRLs.

Computational modeling, fabrication, and characterization of the deep eutectic solvent-based green molecular cage for selective metronidazole extraction from plasma followed by UHPLC with diode array detector determination.

Four ternary deep eutectic solvents were computationally designed and synthesized, being used as candidate functional monomers in metronidazole molecular imprinting polymer synthesis, allowing selective extraction and determination by ultra high performance liquid chromatography with diode array detection. In terms of metronidazole selective extraction, the best results were obtained by (deep eutectic solvent)2 :(ethylene glycol dimethacrylate)11 , in which deep eutectic solvent is the functional monomer constructed by combining three components in 6:6:2 ratios of choline chloride:ethylene glycol:methacrylic acid. The effects of different parameters on molecular imprinted solid-phase extraction of metronidazole were thoroughly explored through screening design and response surface methodology. The adsorption mechanism findings show that the adsorption data are primarily fitted on the Freundlich model based on higher correlation coefficient. Kinetic experiments have shown that the mechanism of adsorption fits the pseudo-second-order model. The best extraction recovery (96.5%) was obtained in 25-min elution time, desorption temperature of 40°C, and 1.0 mL ACN as eluent. Metronidazole was measured by a validated ultra high performance liquid chromatography with diode array detection method. The calibration of the method was linear in the range of 0.1-10 µg/mL with limits of detection and quantification of 0.03 and 0.1 µg/mL, respectively. The method was successfully applied for the determination of metronidazole in human plasma.

Experimental central composite design-based dispersive liquid-liquid microextraction for HPLC-DAD determination of diazinon in human urine samples: method development and validation.

Diazinon poisoning is an important issue in occupational, clinical, and forensic toxicology. While sensitive and specific enough to analyse diazinon in biological samples, current methods are time-consuming and too expensive for routine analysis. The aim of this study was therefore to design and validate a simple dispersive liquid-liquid microextraction (DLLME) for the preparation of urine samples to be analysed for diazinon with high performance liquid chromatography with diode-array detector (HPLC-DAD) to establish diazinon exposure and poisoning. To do that, we first identified critical parameters (type and volume of extraction and disperser solvents, pH, surfactant, and salt concentrations) in preliminary experiments and then used central composite design to determine the best experimental conditions for DLLME-HPLC-DAD. For DLLME they were 800 µL of methanol (disperser solvent) and 310 µL of toluene (extraction solvent) injected to the urine sample rapidly via a syringe. The sample was injected into a HPLC-DAD (C18 column, 250×4.6 mm, 5 µm), and the mobile phase was a mixture of acetonitrile and buffer (63:37 v/v, pH 3.2; flow rate: 1 mL/ min). Standard calibration curves for diazinon were linear with the concentration range of 0.5-4 µg/mL, yielding a regression equation Y=0.254X+0.006 with a correlation coefficient of 0.993. The limit of detection and limit of quantification for diazinon were 0.15 µg/mL and 0.45 µg/mL, respectively. The proposed method was accurate, precise, sensitive, and linear over a wide range of diazinon concentrations in urine samples. This method can be employed for diazinon analysis in routine clinical and forensic toxicology settings.

Cerium-doped flower-shaped ZnO nano-crystallites as a sensing component for simultaneous electrochemical determination of epirubicin and methotrexate.

A glassy carbon electrode (GCE) was modified with cerium-doped ZnO nanoflowers (Ce-ZnO/GCE) to obtain a sensor for direct simultaneous detection of the cancer drugs epirubicin and methotrexate. XRD, SEM and EDX techniques were used to characterize their morphology and structure. Electrochemical impedance spectroscopy was applied to characterize the electrochemical features of the modified GCE. The experimental conditions were optimized. Diffusion coefficients and heterogeneous rate constants were determined for the oxidation of epirubicin. The differential pulse voltammetric response to epirubicin has a peak near 0.7 V (vs. Ag/AgCl at a scan rate of 50 mV s-1) and is linear in the 0.01 to 600 µM concentration range, and the detection limit is 2.3 nM (S/N = 5). The differential pulse voltammetric response to methotrexate has a peak near 0.75 V (vs. Ag/AgCl and the same scan rate) and is linear in the 0.01 to 500 µM concentration range, and the detection limit is 6.3 nM (S/N = 5). The method was applied to the simultaneous determination of epirubicin and methotrexate in pharmaceutical injections and in spiked diluted blood specimens. Graphical abstractSchematic of an electrochemical sensor based on Ce-doped ZnO nano-flowers modified glassy carbon electrode for detecting epirubicin.

The effect of ultrasonic irradiation on the morphology of NiO/Co3O4 nanocomposite and its application to the simultaneous electrochemical determination of droxidopa and carbidopa.

The present work deals with the preparation of NiO/Co3O4 nanocomposites in presence of ultrasonic irradiation, and its use in electrochemical determination of Parkinson's drugs. NiO/Co3O4 nanocomposites are prepared using ultrasound assisted method. The impact of ultrasonic irradiation power (0, 75, 150, 300 and 600 W) on the structure and morphology of NiO/Co3O4 nanocomposites was investigated. Various particle morphologies were attained because of the existence of ultrasonic irradiation. The nanoparticles' structure exhibited more uniformity whilst the particles sizes and nanoparticle accumulation was reduced when ultrasonic irradiation power was increased. The NiO/Co3O4 nanocomposite was determined via X-ray diffraction, scanning electron microscopy i.e. SEM as well as energy dispersion X-ray spectroscopy (EDX). Drop casting NiO/Co3O4 nanocomposites suspension on glassy carbon electrode was employed to fabricate the modified glassy carbon electrode (NiO/Co3O4/GCE). The electrochemical studies on the NiO/Co3O4 nanocomposite towards droxidopa and carbidopa were experimented via cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV). The CV examinations displayed increased catalytic behavior of droxidopa because of synergistic impact of the nanocomposite that was bolstered through enhanced material surface roughness. By using differential pulse voltammetry, the droxidopa detection limit and linear range was determined as 0.01 µM and 0.1-500.0 µM, respectively. Also, the adjusted electrode was implemented to ascertain droxidopa in the presence of carbidopa by differential pulse voltammetry. This sensor exhibited long term reproducibility and stability. Droxidopa and carbidopa quantification within biological specimens of fluids i.e. human urine and serum were conducted to validate the suitability in the application of this sensor.

Computational design as a green approach for facile preparation of molecularly imprinted polyarginine-sodium alginate-multiwalled carbon nanotubes composite film on glassy carbon electrode for theophylline sensing.

This paper reports on the synthesis of a novel molecularly imprinted composite film using the mathematical modeling. This composite was then used in the electrode modification for the determination of theophylline. The ratio of monomer to template in optimum condition was obtained to be 4. The modification of electrode was performed in the presence of theophylline through the electropolymerization of arginine on the composite of sodium alginate/multiwalled carbon nanotubes (SA-MWCNTs), which had been coated on glassy carbon electrode (GCE). The SA-MWCNTs composite with netlike morphology demonstrated high conductivity and electrocatalytic activity. Cyclic voltammogram of modified electrode (MIP/SA-MWCNTs/GCE) in the presence of theophylline showed a sensitive anodic peak in 1170 mV in buffer solution of phosphate (pH 7.0). The investigation and optimization of the effective factors on the response and electrochemical behavior of target theophylline were accurately done on the surface of the modified electrode. Theophylline response was linearly within the range of 0.01-60.0 µM with detection limit of 3.2 nM. Regarding the added standards, the recoveries were values between 93.4-105%. The function of this electrode was satisfactory in the determination of theophylline in real samples like theophylline tablet, theophylline oral solution and human plasma samples.

Preparation and Evaluation of the Antibacterial Effect of Magnetic Nanoparticles Containing Gentamicin: A Preliminary In vitro Study.

BACKGROUND: Magnetic nanoparticles (MNPs) loaded by various active compounds can be used for targeted drug delivery. Objectives: In the present study, the Fe3O4 magnetic nanoparticles that contained gentamicin were prepared and their antibacterial activities were studied. MATERIALS AND METHODS: MNPs containing gentamicin (G@SA-MNPs) were prepared using sodium alginate (SA) as a surface modifier. After and before coating, the prepared MNPs were characterized using transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM). Finally, the antibacterial effect of the MNPs was investigated by a conventional serial agar dilution method. RESULTS: Particle size distribution analysis showed that the size of MNPs, before and after coating, was in the range of 1-18 nm and 12-40 nm, respectively. The magnetization curve of G@SA-MNPs (with saturation magnetization of 27.9 emu.g-1) confirmed ferromagnetic property. Loading gentamicin on the surface of MNPs was qualitatively verified by FTIR spectrum. Quantitative analysis measurements indicated the gentamicin loading on SA-MNPs as 56.7 ± 5.4%. The measured MICs of G@SA-MNPs for Pseudomonas aeruginosa (PTTC 1574) was 1.28 µg.mL-1. The sub-MIC (0.64 µg.mL-1) concentration of G@SA-MNPs in nutrient broth could successfully inhibit the growth of P. aeruginosa for 14 hours. CONCLUSIONS: Loading gentamicin on the SA-MNPs exhibited reasonable antibacterial effects against P. aeruginosa.

Selective extraction of morphine from biological fluids by magnetic molecularly imprinted polymers and determination using UHPLC with diode array detection.

The determination of morphine concentration in the blood and urine is necessary for patients and recruitment purposes. Herein, a magnetic molecularly imprinted polymer for selective and efficient extraction of morphine from biological samples was synthesized by using a core-shell method. Fe3 O4 nanoparticles were coated with SiO2 -NH2 . The molecularly imprinted polymer was coated on the Fe3 O4 /SiO2 -NH2 surface by the copolymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of morphine as the template molecule. The morphological and magnetic properties of the polymer were investigated. Field-emission scanning electron microscopy indicated that the prepared magnetic polymer is almost uniform. The saturation magnetization values of Fe3 O4 nanoparticles, Fe3 O4 /SiO2 -NH2 , and the magnetic polymer were 48.41, 31.69, and 13.02 emu/g, respectively, indicating that all the particles are superparamagnetic. Kinetics of the adsorption of morphine on magnetic polymer were well described by second-order kinetic and adsorption processes and well fitted by the Langmuir adsorption isotherm, in which the maximum adsorption capacity was calculated as 28.40 mg/g. The recoveries from plasma and urine samples were in the range of 84.9-105.5 and 94.9-102.8%, respectively. By using the magnetic molecularly imprinted polymer, morphine can selectively, reliably, and in low concentration be determined in biological samples with high-performance liquid chromatography and UV detection.

Computer-aided design and synthesis of a highly selective molecularly imprinted polymer for the extraction and determination of buprenorphine in biological fluids.

Buprenorphine is widely used to aid the cessation of opioids in addicted patients. To the best of our knowledge, there is no selective extraction method for buprenorphine from biological fluids. Here, we describe the synthesis of a molecularly imprinted polymer with the aid of computational design and its application for selective extraction of buprenorphine from plasma and urine. Computational design was used to study intermolecular interactions in the pre-polymerization mixture by the comparison of the binding energy between buprenorphine (template) and functional monomers. The largest interaction energy of template-monomers was obtained at ratio of 1:5 buprenorphine/acrylic acid monomers. Afterwards, the molecularly imprinted polymer was synthesized through precipitation polymerization technique and was employed for selective extraction of buprenorphine. Optimization of various parameters of the molecularly imprinted polymer solid-phase extraction of buprenorphine was carried out by a design of experiment approach using a central composite design and the analyte was determined by employing high-performance liquid chromatography with UV detection. Equilibrium isotherms were studied, and results revealed that the sorption process was in adoption with Langmuir model. Maximum enrichment capacity and Langmuir constant were calculated as 18.2 mg/g and 0.797 L/mg, respectively. Kinetic studies indicated the sorption process followed a pseudo-second-order model.

Computation-Assisted Molecularly Imprinted Polymer Synthesis for Extraction of Naltrexone from Urine Using Experimental Design and Determination by UPLC-DAD.

To design a molecularly imprinted polymer (MIP) for naltrexone, calculations were performed using Gaussian 03 software, and the interaction energy (ΔE) of template-monomer complexes was estimated using the density functional theory method with the B3LYP function and 6-311G (d) basis set. The effect of different solvents in the polymerization process was studied using the polarizable continuum model. It was shown that five molecules of methacrylic acid gave the largest ΔE with tetrahydrofuran as the polymerization solvent. Effective factors of the removal efficiency of naltrexone by the MIP were selected using a central composite design, and thereafter, the optimization of significant factors was performed by response surface methodology. The results predicted through these models showed good agreement with experimental values. The adsorption amount, selectivity distribution coefficient, and selectivity coefficient were found to be 11.60 mg/g, 35.31, and 2.27, respectively. Experiments of naltrexone adsorption onto the MIP were in accordance with the first-order and Langmuir-Freundlich adsorption models. By applying the data to the Scatchard equation, the KD and Qmax were determined as 526.31 mg/L and 19.47 mg/g, respectively.

Zinc oxide-copper oxide nanoplates composite as coating for solid phase microextraction combined with high performance liquid chromatography-UV detection for trace analysis of chlorophenols in water and tomato juice samples.

In the present research, the ZnO-CuO nanoplate composite (ZCNC), solid-phase microextraction (SPME) fiber coating, was prepared and its extraction capability for certain chlorophenols (CPs) was studied through directly sampling the typical CPs mixed standard solution of 4-chlorophenol, 2,3-dichlorophenol, 2,5-dichlorophenol, and 2,4,6-trichlorophenol with high performance liquid chromatography. ZCNC thickness was in the range of 50-65 nm. The effective variables on ZCNC-SPME extraction efficiency were extraction time, salt percentage, and desorption time. Accordingly, a multivariate strategy was applied based on an experimental design by using central composite design for optimizing the significant factors affecting the extraction efficiency. The detection limit and relative standard deviation (RSD) (n = 6), that include repeatability and reproducibility as the target analytes, were in the range of 0.5-5 ng ml(-1) and 5.1-14 % of standard solutions at 50 ng ml(-1) concentration of CPs, respectively. The developed technique is believed to be successfully applicable to preconcentration and determination of target analytes in environmental water and tomato juice samples. Graphical Abstract Application of zinc oxide-copper oxide nanoplates composite for extraction of chlorophenols in water and tomato juice samples and optimizing condition by experimental design method.

Teucrium polium L. extract adsorbed on zinc oxide nanoparticles as a fortified sunscreen.

INTRODUCTION: Zinc oxide nanoparticles (ZnOn) have been used as carriers and sun-protecting agents for Teucrium polium L. extract to enhance sun protection. ZnOn was synthesized by hydrolyzing zinc acetate using sodium hydroxide with mean particle diameter less than 500 nm. MATERIALS AND METHODS: Top flowerings of T. polium L. were extracted by percolation method with petroleum ether, chloroform, and 80% methanol consecutively. Methanolic extract was lyophilized and used as a flavonoid-rich fraction. Sunscreen was prepared by the reconstitution of 0.5 g of the lyophilized extract in water and mixing with 0.5 to 2 g zinc-oxide (ZnO). Sun protection factor (SPF) of the aqueous extract of T. polium, the prepared gel, as well as the zinc oxide suspension alone and in combination with each other was determined spectrophotometrically based on a modified Transpore(®) tape method. RESULTS AND CONCLUSION: Obtained results showed that the T. polium extract has a wide band of ultraviolet radiation (UV) spectrum absorption ranging from 250 nm to 380 nm. SPF of the combination product in the ultraviolet B (UVB) area was greater than 80, revealing a synergistic action between ZnO and T. polium. The adsorption of flavonoids of T. polium on Zinc-oxide nanoparticles (ZnOn) slowed down their release thereby lengthening their persistence on the skin and contributing to further duration of action.

Gabapentin Determination in Human Plasma and Capsule by Coupling of Solid Phase Extraction, Derivatization Reaction, and UV-Vis Spectrophotometry.

Gabapentin is an anticonvulsant widely used in the treatment of epilepsy. No peculiar chromophore is available on the gabapentin moiety for direct analysis by absorption spectrophotometry. A sensitive spectrophotometric method for the determination of gabapentin in bulk, pharmaceutical formulations and human plasma has been developed. In this method, gabapentin directly derivatized with vanillin and analyzed without any extraction in bulk and pharmaceutical dosage form and in plasma samples, it was extracted with a reversed-phase solid-phase extraction (SPE) cartridge followed by derivatization with vanillin. Analysis was performed by a spectrophotometer system. The quantitation limit of gabapentin in human plasma was 0.8 mg/L. The method was linear over the concentration range of 10.0-90.0 mg/L and 0.8-10.0 mg/L for pharmaceutical dosage form and plasma, respectively. The method was precise (relative standard deviation, RSD <1.20%) and accurate (relative mean error <5.5%) for both pharmaceutical dosage form and plasma samples. Mean absolute recoveries were 94.5% for plasma.

A qualitative survey of five antibiotics in a water treatment plant in central plateau of Iran.

INTRODUCTION: This study aimed to survey a total of five common human and veterinary antibiotics based on SPE-LC-MS-MS technology in a water treatment plant at central plateau of Iran. Also two sampling techniques, passive and grab samplings, were compared in the detection of selected antibiotics. MATERIALS AND METHODS: In January to March 2012, grab and passive samples were taken from the influent and effluent of a water treatment plant. The samples were prepared using solid-phase extraction (SPE), and extracts were analyzed by liquid chromatography tandem mass spectrometry (LC-MS-MS). RESULTS: The results showed that enrofloxacin, oxytetracycline, and tylosin were not detected in none of the samples. However, ampicillin was detected in the grab and passive samples taken from the influent (source water) of the plant, and ciprofloxacin was detected in passive samples taken from the influent and effluent (finished water) of the plant. CONCLUSION: The results imply that passive sampling is a better approach than grab sampling for the investigation of antibiotics in aquatic environments. The presence of ampicillin and ciprofloxacin in source water and finished water of the water treatment plant may lead to potential emergence of resistant bacteria that should be considered in future studies.

Removal of lead, cadmium, zinc, and copper from industrial wastewater by carbon developed from walnut, hazelnut, almond, pistachio shell, and apricot stone.

In this work, adsorption of copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) that exist in industrial wastewater onto the carbon produced from nutshells of walnut, hazelnut, pistachio, almond, and apricot stone has been investigated. All the agricultural shell or stone used were ground, sieved to a defined size range, and carbonized in an oven. Time and temperature of heating were optimized at 15 min and 800 degrees C, respectively, to reach maximum removal efficiency. Removal efficiency was optimized regarding to the initial pH, flow rate, and dose of adsorbent. The maximum removal occurred at pH 6-10, flow rate of 3 mL/min, and 0.1g of the adsorbent. Capacity of carbon sources for removing cations will be considerably decreased in the following times of passing through them. Results showed that the cations studied significantly can be removed by the carbon sources. Efficiency of carbon to remove the cations from real wastewater produced by copper industries was also studied. Finding showed that not only these cations can be removed considerably by the carbon sources noted above, but also removing efficiency are much more in the real samples. These results were in adoption to those obtained by standard mixture synthetic wastewater.

The study of drug permeation through natural membranes.

In this study, natural membranes such as the outer membrane of Prunus persica (peach) and Lycopersicon esculentum (tomato), the inner layer of the egg of Gallus domesticus (hen) and the middle membrane of the Allium cepa (onion) were used as controlling barriers for permeation of some model drugs with different MW and lipophilicities. Drug permeation studies were done by using modified Franz diffusion cell. The permeation of drugs through these natural membranes was compared to permeation of them through human skin and synthetic cellophane membrane. Results showed that the rate and amount of diclofenac permeated through onion membrane was not significantly different from that with tomato (p>0.17), egg (p>0.29) and human skin (p>0.93). Permeation of diclofenac through tomato skin and cellophane was not significantly different (p>0.35). Permeation of diclofenac through all studied membranes except for human skin that follows the Fickian kinetic followed non-Fickian mechanism and their permeabilities were not significantly different from each other (p>0.05). Permeation of metronidazole through onion membrane and tomato skin were not significantly different from human skin (p>0.053 and 0.38, respectively). All membranes were significantly different from each other (p<0.0001) for permeation of erythromycin as a relatively large molecular weight and lipohilic molecule through human skin and other studied membranes. Permeation of diclofenac through human skin and metronidazole through egg and tomato skin followed Fick's first law. Diffusion of diclofenac through onion, tomato, egg, cellophane, and peach; metronidazole through onion, peach, cellophane, and human skin, and erythromycin through all studied membranes followed non-Fickian mechanism for diffusion. Statistical analysis showed the most similarity between onion and human skin for diclofenac, tomato and human skin for metronidazole, onion and cellophane for erythromycin.

A comparative study of first-derivative spectrophotometry and high-performance liquid chromatography applied to the determination of losartan potassium in tablets.

Losartan, a highly effective blood pressure-lowering agent, has been widely used for the treatment of hypertension. A fast and reliable method for the determination of losartan was highly desirable to support formulation screening and quality control. A first-derivative UV spectroscopic method and HPLC were developed for the determination of losartan in the tablet dosage form. The first-derivative spectrum recorded between 220 and 320 nm and a zero-crossing technique for first-derivative measurement at 232.5 nm were selected. The selectivity and sensitivity of the method was in desirable range. In comparison with the direct UV method, first-derivative UV spectroscopy has a definite trough without any interference from UV absorbing-excipients. This method is also fast and economical in comparison with the more time-consuming HPLC method regularly used for formulation screening and quality control and can be used routinely by any laboratory possessing a spectrophotometer with a derivative accessory. The linear concentration ranges were 2-50 microg ml(-1), (D(1)=-0.0159C-0.0056, r=0.9994, n=6). Between-days CV of < or =2.9%, within-day CV of < or =2.1%, and analytical recovery close to 98.1% show the suitability of the method for determination in quality control.

A new second-derivative spectrophotometric method for the determination of permethrin in shampoo.

Permethrin, a highly effective insecticide agent, has been widely used for the pest control in agriculture and the treatment of lice in human. A fast and reliable method for the determination of permethrin was highly desirable to support formulation screening and quality control. A second-derivative UV spectroscopic method was developed for the determination of permethrin in the shampoo dosage form after extraction. The second-derivative spectrum recorded between 250 and 310 nm, and a zero-crossing technique for second-derivative measurement at 279 nm was selected. It is found that the selectivity and sensitivity of the method to be in desirable range. In comparison with the direct UV method, second-derivative UV spectroscopy eliminates the interference from UV absorbing excipients. This method is also fast and economical in comparison with the more time-consuming GC method regularly used for formulation screening and quality control and can be used routinely by any laboratory possessing a spectrophotometer with a derivative accessory. The linear concentration ranges were 0.25-1.5 ppm (D2=0.00042Conc.+0.0018, r=0.9972, n=10). Between day of CV%