Rapid analysis of 2,4-D in soil samples by modified Soxhlet apparatus using HPLC with UV detection

The 2,4-dichlorophenoxy acetic acid (2,4-D) is used as a systemic herbicide to control broadleaf weeds in wheat, corn, range land/pasture land, sorghum, and barley. In this study, a fast and efficient method is developed by selection of modified extraction apparatus and high-performance liquid chromatography (HPLC)-UV conditions for the determination of 2,4-D in soil samples. The method is applied to the study of soil samples collected from the agricultural field. The herbicide is extracted from soil samples by acetonitrile in a modified Soxhlet apparatus. The advantages of the apparatus are that it uses small volume of organic solvent, reduced time of extraction, and better recovery of the analyte. The extract is filtered using a very fine microfiber paper. The total extract is concentrated in a rotatory evaporator, dried under ultrahigh pure N2, and finally reconstituted in 1 mL of acetonitrile. HPLC-UV at 228 nm is used for analysis. The herbicide is identified and quantitated using the HPLC system. The method is validated by the analysis of spiked soil samples. Recoveries obtained varied from 85% to 100% for spiked soil samples. The limit of quantitation (LOQ) and the limit of detection (LOD) are 0.010 and 0.005 parts per million (ppm), respectively, for spiked soil samples. The LOQ and LOD are 0.006 and 0.003 ppm for unspiked soil samples. The measured concentrations of 2,4-D in spiked soil samples are between 0.010 and 0.020 ppm with an average of 0.016 +/- 0.003 ppm. For unspiked soil samples it is between 0.006 ppm and 0.012 ppm with an average of 0.009 +/- 0.002 ppm. The measured concentrations of 2,4-D in soil samples are generally low and do not exceed the regulatory agencies guidelines.     

Silver Selective Electrode Based on Hybrid Mesoporous Silica (MCM‐41) Modified Material

A silver selective electrode based on TEPQA‐MCM‐41 material was developed and used for the selective determination of Ag⁺ ion in various samples. The effect of various plasticizers i. e. dimethyl phthalate (DMP), Tris(ethylhexyl)phosphate (TEP), bis‐(2‐ethylhexyl)sebacate (BEHS), bis‐(2‐ethylhexyl)adipate (BEHA) was investigated. The electrode of the composition of 2 : 1 : 77 : 12 : 8 (w/w, %) of TEPQA‐MCM‐41 : NaTPB : Graphite powder : paraffin oil : DMP respectively, works satisfactorily in a wide concentration range of 1.3×10^?9 M–1.0×10^?1 M for Ag⁺ ion with a lower detection limit (LOD) of 1.0×10^?9 M and has Nernstian slope of 63.4 1 mV/decay. The electrode can be used in a pH range of 2.3 to 6.7 for a period of 3 months without any divergence in potential response. The selectivity coefficient calculated by fixed interference method indicates the high selectivity of the electrode towards Ag⁺ ion over other tested cations.     

Equilibrium anionic polymerization of α-methylstyrene in p-dioxane

The equilibrium anionic polymerization of α-methylstyrene in p-dioxane, with potassium as initiator, has been investigated at 5, 15, 25, and 40°C by using high-vacuum techniques. The comparison of these results with those obtained previously for the equilibrium polymerization of α-methylstyrene in tetrahydrofuran revealed that, although the values of ΔG_1c, the free-energy change upon the polymerization of 1 mole of liquid monomer to 1 bases-mole of liquid amorphous polymer of infinite chain length, are the same for both systems, there is a distinct effect of the solvent. This effect is reflected in the value of monomer equilibrium concentration and its variation with polymer concentration and is explained in terms of a solvent–monomer and solvent–polymer interaction parameter.     

Acceptor properties of titanium(IV) phenoxides

Summary Compounds of composition TiCl_4–n(OPh)_n · 2L (L = monodentate ligand, n = 1–4) have been prepared by the reaction of the parent titanium phenoxides (1 mol) with the ligand (2 mols) and characterized by elemental analysis, molar conductance, molecular weight and i.r. spectral studies.     

UVB-induced photodamage to phycobilisomes of Synechococcus sp. PCC 7942

The effect of UVB irradiation on the phycobilisomes (PBSs) of Synechococcus sp. PCC 7942 cells was studied. The sucrose density-gradient-isolated PBSs from in vivo UVB-treated (280–320 nm) cells showed a strong decrease in β-phycocyanin (βPC) and -phycocyanin (PC) polypeptides. In addition to a decrease in the linker polypeptides LCM 75 (linker connecting the core to the thylakoid membranes), LR 33 (linker in the rod structure), LRC 31.5 (linker connecting the rod to the core) and LRC 29. In vitro UVB treatment of gradient-isolated intact PBSs for 1 h had no effect on any of the constituent polypeptides, and only after 2 h was a degradation of LCM 75 and LR 33 and a decrease in βPC evident. Further investigation of phycobiliproteins (4 h of UVB irradiation) using polyclonal antibody directed against purified whole PBSs revealed that, in vivo, there was a gradual decline in the levels of LCM 75, LR 33, LRC 31.5, LRC 29, βPC and PC.     

Determination of strange quark suppression in hadronic vacuum

We study the forward-backward rapidity correlation slope in \(\bar p\) p interactions at high energies. We show that the measurement of this slope in different rapidity intervals, yields direct information on multiple-scattering. It turns out that the particles produced in inelastic rescattering are concentrated neary=0. This is a key feature of the multi-chain dual parton model, and leads to a simple explanation of the main features of multi-hadron production at very high energies, such as the energy dependence of the height and shape of the rapidity distribution, approximate K.N.O. scaling etc. We also show that the large values of the forward-backward correlation slope measured at ISR and SPS, are obtained in the model using the standard idea of short-range order in a single inelastic collision.     

1,1,1,1-Tetrakis(o-fluorophenylamino)silane tris[titanium(IV) chloride]. Evidence for a new titanium cation [Ti2Cl7]+

Si(NHC₆H₄F-o)₄ · 3TiCl₄ (1) has been obtained from the disproportionation of (CF₃CH₂O)₃SiNHC₆H₄F-o and TiCl₄ in petroleum ether (40–60 °C) at –10 °C. The analytical (elemental analysis, molar conductance) and spectral (i.r., ¹H- and ¹⁹F-n.m.r.) data suggested that (1) behaves as [Si(NHC₆H₄F-o)₄ · Ti₂Cl₇]⁺ [TiCl₅]^–. The presence of these ions has been confirmed by characterising the products of metathetical reactions of (1) with R₄NX (R = Bu and Et; X = I and Br) and with AgNO₃. The data suggest the presence of a new titanium cation [Ti₂Cl₇]⁺.     

Nanostructured ZrO2 and Zr‐C‐N Coatings from Chemical Vapor Deposition of Metal‐Organic Precursors

Nanocrystalline zirconium carbonitride (Zr‐C‐N) and zirconium oxide (ZrO₂) films were deposited by chemical vapor deposition (CVD) of zirconium‐tetrakis‐diethylamide (Zr(NEt₂)₄) and ‐tert‐butyloxide (Zr(OBu^t)₄), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The Zr‐C‐N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et₂NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr‐C‐N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt₂)₄ and Et₂NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt₂)₄. Subject to the precursor composition and deposition temperature (550‐750 °C), the microhardness values of Zr‐C‐N films were found to be in the range 2.11‐5.65 GPa. For ZrO₂ films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350 °C show tetragonal ZrO₂ to be the only crystalline phase. Upon increasing the deposition temperature to 450 °C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650 °C), pure monoclinic phase was obtained with facetted grains and developed texture.     

Ru(II) complexes imparting N2O2 donor bis chelating ligand N,N-bis(salicylidine)-hydrazine in unusual coordination mode

The synthesis and characterization of binuclear ruthenium complexes [{(η⁶-C₆H₆)Ru}₂(μ-bsh)₂] (1), [{(η⁶-C₁₀H₁₄)Ru}₂(μ-bsh)₂] (2), [{(η⁶-C₆Me₆)Ru}₂(μ-bsh)₂] (3), and rhodium complex [{(η⁵-C₅Me₅)RhCl}₂(μ-bsh)] (4) (bsh=N,N^′-bis(salicylidine)-hydrazine dianion) are reported. The complexes have been fully characterized by analytical and spectral techniques and unusual coordination mode of the ligand H₂bsh has been confirmed by single crystal X-ray analysis of the complex 2. Structural data revealed extensive inter- and intra-molecular C-H?O and C-H?π interactions and involvement of methyl and isopropyl hydrogen from the p-cymene in hydrogen bonding.     

Hydroarylation of alkynes and alkenes through alumina-sulfuric acid catalyzed regioselective CC bond formation

A highly atom-efficient synthetic protocol for hydroarylation of terminal-aryl alkynes and styrene through the regioselective CC bond formation via the electrophilic addition of naphthols and substituted phenols has been developed using alumina-sulfuric acid as a heterogeneous supported solid acid catalyst. This methodology shows excellent regioselectivity and affords the desired product in good to excellent yield. The heterogeneous catalyst can also be recycled efficiently without much loss of activity.