Highly selective PVC-membrane electrodes based on Co(II)-Salen for determination of nitrite ion.

A cobalt(II) derivative was used as a suitable ionophore for the preparation of a polymeric membrane nitrite-selective electrode. The electrode reveals a Nemstian behavior over a very wide NO2- ion concentration range (1.0 x 10(-6)-1.0 x 10(-1) M) and a very low detection limit (5.0 x 10(-7) M). The potentiometric response is independent of the pH of solution in the pH range 4.0-9.5. The electrode shows advantages such as low resistance, fast response and, most importantly, good selectivity relative to a wide variety of inorganic and organic anions. In fact, the selectivity behavior of the proposed NO2- ion-selective electrode shows great improvements compared to the previously reported electrodes for nitrite ion. The proposed electrodes could be used for at least 2 months without any significant changes in potentials. The electrode was successfully applied to the determination of nitrate ion concentrations in sausage and milk samples.     

Homogeneous Liquid–Liquid Microextraction Via Flotation Assistance (HLLME-FA) Method for the Pretreatment of Organochlorine Pesticides in Aqueous Samples and Determination by GC–MS

This work proposes a new, rapid and simple homogeneous liquid–liquid microextraction via flotation assistance technique for the analysis of six organochlorine pesticides in water samples. A special extraction cell was used to facilitate collection of the low-density solvent extract. No centrifugation was required in this procedure. Determination was carried using gas chromatography–mass spectrometry. The water sample solution was then added into the extraction cell containing appropriate mixture of extract and homogeneous solvents. In the first step, a homogeneous solution and then with the continuation of water sample injection, a cloudy solution was formed. Using air flotation, the organic solution was collected at the conical part of the designed cell. The optimized levels of effective parameters were found based on response surface methodology approach. Applying the optimized conditions to the system understudy, the limits of detection of all target analytes were obtained in the range of 1.4–7 ng mL^?1, while the precisions were found to be in the range of 11.08–14.87 (RSD, n = 3). The linearity of the method lay in the range of 10–150 ng mL^?1 with the coefficients of correlation (r ² ) ranging from 0.998 to 0.999.     

Bis (trans-cinnamaldehyde) ethylene diimine dibromonickel (II) complex as a neutral carrier for salicylate-selective liquid membrane and coated graphite sensors

A salicylate PVC-based membrane (SPME) and a coated graphite membrane (SCGE) electrodes by using a new tetracoordinate organonickel complex as ion carrier were prepared. Both sensors show a Nernstian response to salicylate ions over a very wide concentration ranges (1.0×10⁻⁵-1.0×10⁻¹ M for SPME and 1.0×10⁻⁶-1.0×10⁻² M for SCGE) in the pH of 7.0. The best selectivities were obtained for the membrane incorporating 30% PVC, 63% plasticizer, 2% cationic additive and 5% ionophore. The electrodes possess satisfactory reproducibility, very short response time (∼10 s) in the whole concentration ranges, and excellent discriminating ability for salicylate ions with respect to the most common organic and inorganic anions. The detection limits of proposed sensors are 5.0×10⁻⁶ and 7.0×10⁻⁷ M for SPME and SCGE, respectively. The electrodes were successfully used for determination of salicylate in biological samples.     

Octadecyl silica membrane disks modified with a new Schiff's base for the preconcentration of lead and copper before their determination in water samples

A simple and fast method for the extraction and determination of ppt level of Pb2+ and Cu2+ ions using octadecyl-bonded silica membrane disks modified by a new tetradentates Schiffs base [Bis(2,4-dimethoxy benzaldehyde) ethylen diimine](TDSB) and inductively coupled plasma atomic emission spectrometry is described. Extraction efficiency, and influence of flow rate, pH, type and the least amount of acid for stripping of Cu2+ and Pb2+ from the modified disks and break through volume were evaluated. The maximum capacity of the membrane disks modified by 5 mg of TDSB used was found to be 347 +/- 7 and 470 +/- 6 microg of copper and lead, respectively. The concentration factor is 500 (for 2500 mL water sample and flow rate of 20 mL min(-1)) and detection limit of the proposed method is 12.5 and 150.5 pg/ml for Cu2+ and Pb2+, respectively. The method was applied to the determination of Cu2+ and Pb2+ ions from various water, wastewater, black tea, and hot pepper samples.     

Investigation of adsorption mechanism of Fe,Cu, and Zn ions in extraction and preconcentration process on synthesized graphene oxide using an indole derivative

Structural Chemistry - 3-(chloro(2-methyl-1H-indol-3-yl)methyl)-2-methyl-1H-indole (MIMI) was chosen for separation and preconcentration of iron (III), copper (II), and zinc by solid-phase...     

Computation of the far-field time domain solution of the scattering problem.

This paper presents a new technique for calculating the time domain (transient) far-field scattered pressure. The scattering problem is divided in two steps; the first step evaluates the field distribution inside the scatterer, and the second step generates the far-field scattered pressure by 3-D Radon transform of these data for each time step and summing over time. The algorithm results in considerable saving in CPU time and memory by simplifying the calculation along the path from scatterer to receiver. This technique can also be used in two dimensions.     

Homogeneous Liquid–Liquid Microextraction Via Flotation Assistance (HLLME-FA) Method for the Pretreatment of Organochlorine Pesticides in Aqueous Samples and Determination by GC–MS

This work proposes a new, rapid and simple homogeneous liquid–liquid microextraction via flotation assistance technique for the analysis of six organochlorine pesticides in water samples. A special extraction cell was used to facilitate collection of the low-density solvent extract. No centrifugation was required in this procedure. Determination was carried using gas chromatography–mass spectrometry. The water sample solution was then added into the extraction cell containing appropriate mixture of extract and homogeneous solvents. In the first step, a homogeneous solution and then with the continuation of water sample injection, a cloudy solution was formed. Using air flotation, the organic solution was collected at the conical part of the designed cell. The optimized levels of effective parameters were found based on response surface methodology approach. Applying the optimized conditions to the system understudy, the limits of detection of all target analytes were obtained in the range of 1.4–7 ng mL⁻¹, while the precisions were found to be in the range of 11.08–14.87 (RSD, n = 3). The linearity of the method lay in the range of 10–150 ng mL⁻¹ with the coefficients of correlation (r ²) ranging from 0.998 to 0.999.

     

2-Amino-4-(4-aminophenyl)thiazole application as an ionophore in the construction of a Lu(III) selective membrane sensor

A derivative of thiazole（AAT） has been explored as a sensing material for preparation a selective Lu（III） PVC-based membrane sensor.The proposed sensor exhibits a Nernstian response over a wide concentration range from 1.0×10^-6 to 1.0×10^-1 mol/L of Lu（Ⅲ） and the detection limit is 5.7×10^-7 mol/L.The sensor response is independent of pH of the solution in the range 3.2-8.8 and possesses the advantages of fast response time（～6） and in particular,good selectivity to the lutetium ions with regard to most common metal ions,and especially all lanthanide ions.     

ppt level detection of samarium(III) with a coated graphite sensor based on an antibiotic.

N-[2-[4-[[[(Cyclohexylamino)carbonyl]amino]sulfonyl]phenyl]ethyl]-5-methyl pyrazine carboxamide (glipizid) was explored as an electro-active material for preparing a polymeric membrane-based sensor selective to samarium ions. The membrane incorporated 30% poly(vinyl chloride) (PVC), 53% benzyl acetate (BA), 11% glipizid and 6% sodium tetraphenyl borate. When coated on the surface of a graphite electrode, it exhibits Nernstian responses in the concentration range of 1.0 x 10(-5) to 1.0 x 10(-10) M, with a detection limit of 8.0 x 10(-11)M samarium. The electrode shows high selectivity towards samarium over several cations (alkali, alkaline earth, transition and heavy metal ions), and specially lanthanide ions. The proposed sensor has a very short response time (< 15 s), and can be used in a wide pH range for at least ten weeks. It was used as an indicator electrode in potentiometric titration of Sm(III) ions with an EDTA solution, and for determination of samarium in binary and ternary mixtures.     

Homogeneous liquid–liquid microextraction via flotation assistance for rapid and efficient determination of polycyclic aromatic hydrocarbons in water samples

In this work, a rapid, simple and efficient homogeneous liquid–liquid microextraction via flotation assistance (HLLME-FA) method was developed based on applying low density organic solvents without no centrifugation. For the first time, a special extraction cell was designed to facilitate collection of the low-density solvent extraction in the determination of four polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). The effect of different variables on the extraction efficiency was studied simultaneously using experimental design. The variables of interest in the HLLME-FA were selected as extraction and homogeneous solvent volumes, ionic strength and extraction time. Response surface methodology (RSM) was applied to investigate the optimum conditions of all the variables. Using optimized variables in the extraction process, for all target PAHs, the detection limits, the precisions and the linearity of the method were found in the range of 14–41 μg L⁻¹, 3.7–10.3% (RSD, n = 3) and 50–1000 μg L⁻¹, respectively. The proposed method has been successfully applied to the analysis of four target PAHs in the water samples, and satisfactory results were obtained.