Flame atomic absorption determination of ultra-trace zinc in environmental samples after pre-concentration by solid phase extraction

A simple, reliable and rapid method for pre-concentration and determination of ultra-trace zinc using octadecyl silica membrane disk modified by a new Schiff base ligand, and flame atomic absorption spectrometry is presented. Various parameters including, pH of aqueous solution, flow rates, the amount of ligand and type of stripping solvents were optimized. The breakthrough volume is greater than 1000 mL with an enrichment factor of more than 200 and 120 ng/Ldetection limit. The capacity of the membrane disks modified by 8 mg of the ligand was found to be 260 µg of zinc. The effects of various cationic interferences on percent recovery of zinc ion were studied. The method was successfully applied for the determination of zinc ion in different samples, especially determination of ultra-trace amount of zinc in waters and plants

Use of switchable solvent liquid phase microextraction for determination of petroleum pollutants in water samples by gas chromatography–mass spectrometry

In this study switchable solvent liquid phase microextraction (SSLPME) followed by GC-MS detection has been developed for preconcentration and determination of total petroleum hydrocarbons (TPHs) in water samples. The extraction technique makes use of 100 μL of a water-immiscible solvent (dipropylamine) that can be solubilized in the aqueous phase in 1:1 ratio using HCl as a reagent. Afterwards, phases separation is induced by the addition of sodium hydroxide. Optimization of the variables affecting this method was carried out in order to achieve the best extraction efficiency. The optimized conditions included: volume of the sample 5 mL, volume of extraction solvent 100 μL, and pH of sample: 12.0. Under the optimum experimental conditions, good limits of detection (0.3–1.21 µg L−1), linearities (R2 > 0.996), and repeatability of extraction (RSDs below 5.6%, n = 5) were obtained. Finally, the developed method was successfully applied to the determination of the target analytes in different types of natural water samples and acceptable recoveries (>84%) were obtained

trans-Bis[1,3-bis­(2-methoxy­phen­yl)triazenido]dimethano­lcadmium(II)

In the title compound, [Cd(C14H14N3O2)2(CH3OH)2], each cadmium(II) center is six-coordinated by an N atom and an O atom of two 1,3-bis­(2-methoxy­phen­yl)triazene ligands and by the O atoms of two methanol mol­ecules. The distorted octa­hedral coordination geometry of the Cd atom has two N and two O atoms in the equatorial plane, and two O atoms in axial positions. The complex is stabilized by intra­molecular O—H⋯O and O—H⋯N hydrogen bonds. In the crystal structure the complexes are linked into chains via inter­molecular C—H⋯π stacking inter­actions. One of the methanol C atoms is disordered with ouccupancies of 0.7:0.3

1,3-Bis(2-ethoxy­phen­yl)triazene

The title compound, C16H19N3O2, exhibits a trans geometry about the N=N double bond in the triazene unit in the solid state, and individual mol­ecules are close to planar with r.m.s. deviations from planarity of 0.065 Å and 0.242 Å for the two independent molecules in the asymmetric unit. Distinct inter­molecular N—H⋯N hydrogen bonds lead to the formation of dimers with an R 2 2(8) graph-set motif. The steric demands of the eth­oxy groups in the ortho position prevent a coplanar arrangement of the two mol­ecules in the dimers and these instead consist of two inter­locked mol­ecules that are related by a non-crystallographic pseudo-twofold rotation axis. Weak C—H⋯π inter­actions between the CH groups and the aromatic phenyl rings also occur

3-(2-Eth­oxy­phen­yl)-1-(3-nitro­phen­yl)triaz-1-ene

The title compound, C14H14N4O3, exhibits a trans geometry about the N=N double bond in the triazene unit. The mol­ecule is approximately planar (r.m.s. deviation = 0.044 Å for all non-H atoms). An intra­molecular N—H⋯O hydrogen bond occurs. In the crystal, C—H⋯N hydrogen bonds lead to the formation of dimers which are, in turn, connected to each other by C—H⋯O hydrogen bonds, forming infinite chains of R 2 2(8) graph-set motif

Complexation Studies of Zn2+, Cu2+, Co2+, Ni2+ and Cd2+ Ions with a Schiff Base Ligand

The complex-formation reactions between Zn2+, Cu2+, Co2+, Ni2+ and Cd2+ ions with, N,N'–Bis-(salicylidene)1,8-diamino-3,6-dioxaoctan Schiff base ligand, has been studied by spectrophotometric  method in acetonitrile at various temperatures. The formation constant (Kf) and the molar absorptivity (ε) of the resulting complexes between ligand and different cations were calculated by fitting the observed absorbance at various [M2+]/[L] mole ratios and found that the stability of the resulting L-M2+ complexes varied in the order Cu2+ &gt; Zn2+ &gt; Co2+ &gt; Ni2+ &gt; Cd2+. The enthalpy and entropy changes of the complexation reaction were determined from the temperature dependence of the formation constants. DOI: http://dx.doi.org/10.17807/orbital.v9i4.1014 </p

Determination of optimal adsorption-desorption conditions for selective removal of Ni(II) from petrochemical samples using ion imprinted nanosorbent

Nanoporous particles Ni(II) ion imprinted polymer (IIP), and non-imprinted polymer (NIP) in the absence of Ni(II) ion, with 18-70 nm dimensions were synthesized, and characterized by Fourier transform infrared, energy dispersive X-ray and nuclear magnetic resonance spectroscopic methods. Then, the surface area, pore size and structural composition of the products were characterized by Brunauer-Emmett-Teller and scanning electron microscope methods. Then, modified electrodes by the IIP for Ni(II) sensing and determination, were constructed and their catalytic activity were investigated by cyclic voltammetric method. Some parameters like desorption solvent, amount of sorbent, pH and contact time were optimized, and the measurements were all conducted under optimal conditions. The optimum pH for maximum sorption was obtained 7.8. In the optimum conditions, the maximum sorbent capacity of the IIP was obtained 371.9 µM/g. The limit of detection and relative standard deviation (n = 5) were obtained 1.3 ng/mLand 1.47%, respectively. The pre-concentration procedure revealed a linear curve within the concentration range of 10-6000 ng/mL and a good linearity with squared correlation coefficient of r2 0.9991 was achieved. The method was applied successfully for determination of Ni(II) ion in petrochemical samples

Determination of Ultra Trace Copper in Water Samples by Differential Pulse Polarography after Solid Phase Extraction

A high selective and sensitive anodic stripping differential pulse polarographic method for determination of ultra-trace amounts of Cu2+ ion in water samples is proposed. The method is based on the separation and preconcentration of Cu2+ on an octadecyl bonded silica (ODBS) membrane disk modified by a recently synthesized triazene ligand, ([1-(ortoacyl benzene)3-(3,4-dichlorobenzene)triazene]). Various parameters such as, pH of aqueous solution (7-8), flow rates (10 mL min-1), the amount of ligand (6.0 mg) and the type of stripping solvent (0.1M nitric acid) have optimized. The breakthrough volume was greater than 500 mL with an enrichment factor of more than 100 and 3.88µg L-1 detection limit. The capacity of the modified disks is 220µg of copper per 6mg of the ligand. The effects of various cationic interferences on the percent recovery of copper ion were studied. The method was successfully applied to the determination of copper ion in different samples. DOI: http://dx.doi.org/10.17807/orbital.v9i5.1093 </p