β-Cyclodextrin-grafted magnetic graphene oxide nanocomposites in ultrasound-assisted dispersive magnetic solid-phase extraction for simultaneous preconcentration of lead and cadmium ions

Research on Chemical Intermediates - This article presents an ultrasound-assisted dispersive magnetic solid-phase extraction method (USA-DMSPE) to preconcentration Cd(II) and Pb(II) simultaneously....     

Sequence‐based prediction of protein–peptide binding sites using support vector machine

Protein–peptide interactions are essential for all cellular processes including DNA repair, replication, gene‐expression, and metabolism. As most protein – peptide interactions are uncharacterized, it is cost effective to investigate them computationally as the first step. All existing approaches for predicting protein – peptide binding sites, however, are based on protein structures despite the fact that the structures for most proteins are not yet solved. This article proposes the first machine‐learning method called SPRINT to make Sequence‐based prediction of Protein – peptide Residue‐level Interactions. SPRINT yields a robust and consistent performance for 10‐fold cross validations and independent test. The most important feature is evolution‐generated sequence profiles. For the test set (1056 binding and non‐binding residues), it yields a Matthews’ Correlation Coefficient of 0.326 with a sensitivity of 64% and a specificity of 68%. This sequence‐based technique shows comparable or more accurate than structure‐based methods for peptide‐binding site prediction. SPRINT is available as an online server at: http://sparks-lab.org/ . © 2016 Wiley Periodicals, Inc.     

Surfactant-assisted transport of lead ion through a bulk liquid membrane containing dicyclohexyl-18-crown-6: efficient removal of lead from blood serum and sea water

The selective and efficient surfactant assisted transport of Pb²⁺ ions using a bulk liquid membrane composed of dicyclohexyl-18-crown-6, as a highly selective carrier, in chloroform solution is reported. In the presence of 6.0 × 10^?2 M P₂O₇ ^4? ions and 10^?3 M sodium dodecylsulfate, as suitable stripping agent and membrane/receiving phase interface modifier, respectively, in the receiving phase and 2.4 × 10^?3 M picric acid, as a counter ion in the source phase, the amount of lead transported across the liquid membrane after 5 h is 100.0 ± 1.1. The designed transport system was successfully applied to the removal of lead from sea water and blood serum samples.     

Supported hydrophobic ionic liquid on magnetic nanoparticles as a new sorbent for separation and preconcentration of lead and cadmium in milk and water samples

We have prepared a highly selective and efficient sorbent for the simultaneous separation and preconcentration of lead and cadmium ions from milk and water samples. An ionic liquid was deposited on the surface of magnetic nanoparticles (IL-MNPs) and used for solid phase extraction of these ions. The IL-MNPs carrying the target metals were then separated from the sample solution by applying an external magnetic field. Lead and cadmium were almost quantitatively retained by the IL-MNPs, and then eluted with nitric acid. The effect of different variables on solid phase extraction was investigated. The calibration curve is linear in the range from 0.3 to 20?ng mL^?1 of Cd(II), and from 5 to 330?ng mL^?1 of Pb(II) in the initial solution. Under optimum conditions, the detection limits are 1.61 and 0.122?μg?L-1 for Pb(II) and Cd(II) respectively. Relative standard deviations (n?=?10) were 2.87?% and 1.45?% for 0.05?μg?mL^-1 and 0.2?μg?mL^-1 of Cd (II) and Pb (II) respectively. The preconcentration factor is 200 for both of ions.

Hydrophobic Deep Eutectic Solvents in Developing Microextraction Methods Based on Solidification of Floating Drop: Application to the Trace HPLC/FLD Determination of PAHs

In this work, we evaluated the applicability of hydrophobic carboxylic acid-based deep eutectic solvents (DESs) as environmentally friendly alternatives to common organic solvents in microextraction methods based on solidification of floating drop (SFD). Due to the limited number of solvents that can be used in SFD, the introduction of new solvents can help in the development of these attractive methods. Deep eutectic solvents consisting of tetra-n-butyl ammonium bromide (TBAB) and carboxylic acids were prepared and used as extraction solvent. They had the desirable characteristics such as low density, suitable freezing point and proper hydrophobicity which make them suitable alternatives to conventional organic solvents for SFD. With the help of the synthesized hydrophobic DESs, a simple, fast, efficient and environmentally friendly microextraction method was developed based on solidification of deep eutectic solvent (SFDES) without using any organic solvent. The proposed organic solvent-less microextraction method based on SFDES was applied in the analysis of polycyclic aromatic hydrocarbons (PAHs) as model compounds in environmental water samples. By coupling this method with high-performance liquid chromatography–fluorescence detection, we achieved low LOD values which is a necessity in the ultra-trace analysis of PAHs in environmental water samples. Under the optimized conditions, good linearity and low limits of detection of 0.7–6.6 ng L^?1 were obtained. The analysis of six PAHs in real water samples gave acceptable relative recoveries ranging from 83 to 117% with 5.4–10.5% intra-day relative standard deviations (RSD) and 4–7.1% interday RSD.

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Preconcentration and Determination of Trace Nickel Using 1-(2-Pyridylazo)-2-Naphtol (PAN) Immobilized on Surfactant-Coated Alumina

A microcolumn of alumina modified with sodium dodecyl sulfate (SDS) and 1-(2-pyridylazo)-2-naphthol (PAN) was prepared for the preconcentration of trace nickel from water samples for a flame atomic absorption spectrometry (FAAS) determination. Under optimized conditions (pH = 4.0; flow rate, 5 mL min^–1) nickel (II) was retained on the column. The nickel collected on the column was eluted with 5 mL of 0.5 M nitric acid. Recovery was greater than 96.7%. A concentration factor of 300 can be achieved by passing 1500 mL of sample through the microcolumn. The relative standard deviation (ten replicate analyses) at the 40 ng mL^–1 level for nickel was 2.4%, and the corresponding limit of detection (based on 3) was 0.06 ng mL^–1. The method was applied to the determination of Ni in waste and mineral waters.     

Laser induced thermal lens spectrometry for cobalt determination after cloud point extraction

A new approach, employing cloud point extraction (CPE) in combination with thermal lens spectrometry (TLS), has been developed for the determination of cobalt. The CPE and TLS methods have good matching conditions for combination because TLS is suitable for low volume samples obtained after CPE and for organic solvents, which are used for dissolving the remaining analyte phase.1-(2-Pyridylazo)-2-naphthol (PAN) was used as a complexing agent and octylphenoxypolyethoxyethanol (Triton X-114) was added as a surfactant; then the pH of solution was adjusted. After phase separation at 50 °C based on the cloud point extraction of the mixture, the surfactant-rich phase was dried and the remaining phase was dissolved using 20 μL of carbon tetrachloride. The obtained solution was introduced into the quartz micro cell and the analyte was determined by thermal lens spectrometry. The He-Ne laser (632.8 nm) was used as both the probe and the excite source.Under optimum conditions, the analytical curve was linear for the concentration range of 0.2-40 ng mL⁻¹ and the detection limit was 0.03 ng mL⁻¹. The enhancement factor of 470 was achieved for a 10 mL sample. Relative standard deviations were lower than 5%.The method was successfully applied to the extraction and determination of cobalt in tap, river and sea water.     

Synthesis of salicylaldehyde-modified mesoporous silica and its application as a new sorbent for separation, preconcentration and determination of uranium by inductively coupled plasma atomic emission spectrometry

A new functionalized mesoporous silica (MCM-41) using salicylaldehyde was utilized for the separation, preconcentration and determination of uranium in natural water by inductively coupled plasma atomic emission spectrometry (ICP-AES).Experimental conditions for effective adsorption of trace levels of U(VI) were optimized. The preconcentration factor was 100 (1.0 mL of elution for a 100 mL sample volume). The analytical curve was linear in the range 2-1000 μg L⁻¹ and the detection limit was 0.5 ng mL⁻¹. The relative standard deviation (R.S.D.) under optimum conditions was 2.5% (n = 10). Common coexisting ions did not interfere with the separation and determination of uranium at pH 5. The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be 10 mg of uranium per gram of sorbent. The method was applied for the recovery and determination of uranium in different water samples.