HPLC Separation of Different Groups of Small Polar Compounds on a Novel Amide-Embedded Stationary Phase

Retention behaviors of an amide-embedded silica base stationary phase, which was recently developed by our group, were studied by using six different groups of small polar compounds including phenolic compounds, substituted anilines, chlorinated herbicides, Sudan dyes and some nucleotides and nucleosides in HPLC. The chromatographic behaviors of the prepared stationary phase for these analytes were compared with those of a commercially available reversed-phase column ACE C18 under same conditions. Among the six groups of analytes studied, the amide-silica stationary phase showed enhanced selectivity towards phenolic compounds, substituted anilines, Sudan dyes and herbicides under reversed-phase conditions and satisfactory selectivity towards nucleosides and nucleotides which could not be separated with ACE C18 column under HILIC conditions. Experimental data provided some evidence that functional groups on the stationary phases might have certain degrees of influence on selectivity possibly through secondary interactions with the model compounds. The retentions of the moderately polar compounds such as phenolic acids, anilines and herbicides on the stationary phase are higher than highly polar compounds such as nucleotides and nucleosides due to both the hydrophobic and hydrophilic interactions between the stationary phase and analytes. The quantitative determination of Sudan dyes (I, II, III, and IV) in red chilli peppers was performed. Many red chilli peppers were screened and three of them contained Sudans dyes.     

Characterization of bidentate phosphoryl compounds on soil particulates using SIMS

The presence of organic compounds as surface contaminants on particles can provide valuable data about the particles environment, but identification can be analytically challenging. This is true particularly for compounds that have the potential for strong surface binding, such as compounds capable of multidentate attachment. Direct analysis using time‐of‐flight secondary ion mass spectrometry was evaluated for characterization of soil particles contaminated with low concentrations of two bidentate organophosphoryl compounds, diphenyl‐N,N‐di‐n‐butylcarbamoylmethylphosphine oxide and tetraphenylmethylene diphosphine dioxide. Molecular ions were formed by cationization with H⁺ and alkali elements Na⁺ and K⁺ that are indigenous to the particle surface chemistry. Spectra generated from a contaminated calcareous soil were dominated by K⁺‐containing ions, whereas spectra from a sandy loam had more abundant Na⁺‐species. Cation‐bound dimers were also formed which favored incorporation of K⁺, and a unique aluminosilicate‐phosphoryl conjugate cation was also formed when the diphosphoryl ligand was present on the surface. The phosphoryl ligands also underwent fragmentation reactions, the course of which varied depending on the cation that was bound. Minimum detectable surface concentrations were evaluated and were in the 0.04–0.2 monolayer range, depending on the compound and soil particle matrix they was bound to. The ion signature was detected on soil particle surfaces for time periods exceeding six months, suggesting that the characterization approach could be used for environmental exposure history at times well beyond initial exposure. Copyright © 2009 John Wiley & Sons, Ltd.     

An electron paramagnetic resonance and density-functional theory study on the methyl isotropic hyperfine coupling constants in gamma-irradiated 2,6-di-tert-butyl-4-methylphenol

Single crystal of gammairradiated 2,6-di-tert-butyl-4-methylphenol (BHT) was investigated using an electron paramagnetic resonance (EPR) technique at different orientations in the magnetic field at room temperatures. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal of BHT, we assumed that one phenoxyltype paramagnetic species was produced having an unpaired electron localized at the methyl fragment side of the phenyl ring. Depending on this assumption, one possible radical was modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radical using the B3LYP/TZVP and B3LYP/EPR-III level. The averaged value of isotropic hydrogen hyperfine coupling constants of rotating methyl functional group of phenoxyl radical is calculated for the first time. Theoretically calculated values of the modeled radical are in reasonably good agreement with the experimental data determined from the spectra (differences in averaged coupling constant values smaller than 5%, and differences in isotropic g values fall into 1 ppt).     

Preparation and characterization of radiolabeled magnetic nanoparticles as an imaging agent

The degradation of crystal violet in aqueous solution was investigated using kaolin-supported zero-valent iron nanoparticles (K-nZVI). It was found that K-nZVI with a ratio of kaolin:zero-valent iron nanoparticles (nZVI) at 1:1 was most effective in removing crystal violet. Batch experiments show that more than 97.29?% crystal violet was degraded using K-nZVI, while only 24.36?% was removed using nZVI after reacting for 7?min, where the solution contained 100?mg?L^?1 crystal violet at pH 6.5. This is due to a decrease in aggregation of Fe⁰ nanoparticles and enhanced their reactivity in the presence of kaolin, which was confirmed by the characterization using scanning electron microscopy. X-ray diffraction shows the formation of iron oxide and hydroxide, while UV?CVis spectral shows that the absorption peak of crystal violet was reduced, as well as Fourier transform infrared shows that new bands were formed after K-nZVI reacting with crystal violet. These suggest that degradation of crystal violet by K-nZVI include the oxidation of iron, the adsorption of crystal violet onto the K-nZVI, the transformation of crystal violet to leuko-crystal violet, and finally the cleavage of C=C bond.     

HEPES-stabilized encapsulation of Salmonella typhimurium

Most bacteria, planktonic and sessile, are encapsulated inside loosely bound extracellular polymeric substance (EPS) in their physiological environment. Imaging a bacterium with its capsule requires lengthy sample preparation to enhance the capsular contrast. In this study, Salmonella typhimurium was investigated using atomic force microscopy for a practical means of imaging an encapsulated bacterium in air. The investigation further aimed to determine the relation between the buffers used for preparing the bacterium and the preservation of the capsular material surrounding it. It was observed that rinsing bacteria with HEPES buffer could stabilize and promote capsule formation, while rinsing with PBS, Tris, or glycine removes most of the capsular EPS. For bacteria rinsed with HEPES and air-dried, the height images showed only the contour of the capsular material, while the phase and amplitude images presented the detailed structures of the bacterial surface, including the flagella encapsulated inside the capsular EPS. The encapsulation was attributed to the cross-linking of the acidic exopolysaccharides mediated by the piperazine moiety of HEPES through electrostatic attraction. This explanation is supported by encapsulated bacteria observed for samples rinsed with N,N'-bis(2-hydroxyethyl)-piperazine solution and by the presence of entrapped HEPES within the dry capsular EPS suggested by micro-Raman spectroscopy.     

Target-Guided Isolation of Progenitors of 1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) from Riesling Wine by High-Performance Countercurrent Chromatography

High-performance countercurrent chromatography (HPCCC) was used for the target-guided isolation of precursors of 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) from Riesling wine. In separated HPCCC fractions of an Amberlite^® XAD^®-2 extract obtained from a German Riesling, TDN-generating fractions were identified by the acid-catalyzed hydrolysis of the progenitors at pH 3.0 and subsequent HS-GC-MS/MS analysis. The presence of multiple TDN-generating precursors in Riesling wine could be confirmed. From polar HPCCC fractions (11–13 and 14–16), 3,4-dihydroxy-7,8-dihydro-β-ionone 3-O-rutinoside and 3,4-dihydroxy-7,8-dihydro-β-ionone 3-O-β-d-glucopyranoside were isolated as major TDN-precursors at a sufficient amount for structure elucidation by NMR spectroscopic studies. In the medium polar HPCCC factions (27–35), enzymatic hydrolysis liberated the aglycones 3-hydroxy-β-ionone and 3-hydroxy-TDN in minor amounts. In further less polar TDN-generation fractions (36–44 and 45–50), glycosidic progenitors were absent; instead, a minor TDN formation most likely from non-conjugated constituents was observed.     

Sonochemical shape control of copper hydroxysulfates

Shape control of inorganic nanoparticles generally requires the use of surfactants or ligands to passivate certain crystallographic planes. Additive free shape control methods utilize the differences in the growth rates of crystallographic planes. We combined this approach with the sonochemical method to synthesize copper hydroxysulfate (Brochantite) with morphologies ranging from flowers, to bricks, belts and needles. Sodium peroxydisulfate, which was used as the sulfate and hydroxide source, was decomposed thermally and/or sonically under various pH and temperature conditions. The relative release rates of the sulfate and hydroxide anions determined the final form of the crystals. This technique yielded products even at acidic pH, marking a distinction from the literature reactions, which start with stoichiometric amounts of sulfate and hydroxide anions and yield only a single crystal morphology.     

Complexes of Iron(III) and Chrom(III) Salen and Saloph Schiff Bases with Bridging 2,4,6-tris(4-nitrophenylimino-4′-formylphenoxy)-1,3,5-triazine

Four new trinuclear Fe(III) and Cr(III) complexes involving tetradenta Schiff bases N,N′-bis(salicylidene)ethylenediamine-(salenH₂) or bis(salicylidene)-o-phenylenediamine-(saloph H₂) with 2,4,6-tris(4-nitrophenylimino-4′-formylphenoxy)-1,3,5-triazine (TNPI-TRIPOD) have been synthesized and characterized by means of elemental analysis carrying out ¹H-NMR., IR spectroscopy, thermal analyses and magnetic susceptibility measurements. The complexes can also be characterized as high-spin distorted octahedral Fe(III) and Cr(III) bridged by nitro. The nitro play a role as bridges for weak anti-ferromagnetic intramolecular exchange.     

ESR of Gamma Irradiation and Ultraviolet Photolysis Products in Some Tetrasubstituted Ammonium Compounds

Abstract

The electron spin resonance of gamma and ultraviolet irradiated tetrabutylammonium halides [CH₃(CH₂)₃]₄NX (X=I,Cl,Br), tetrabutylammonium hydrogen sulfate [CH₃(CH₂)₃]₄NHSO₄, tetrabutylammonium periodate [CH₃(CH₂)₃]₄NIO₄, and ultraviolet photolyzed tetramethylammonium iodide, (CH₃)₄NI, and tetramethylphosphonium iodide, (CH₃)₄PI have been investigated between 140 and 350 K. The gamma and ultraviolet irradiation damage centers in tetrabutylammonium compounds were attributed to CH₃—CH^…—CH^…—CH₂, radicals, and ultraviolet photolysis damage centers in tetramethylammonium and phosphonium iodides were attributed to ?H₃ radicals. The g values of both radicals are found to be isotropic and g = 2.0030 and 2.0037 respectively to the methylallyl and the methyl radicals. The hyperfine coupling constants of the free electron to the protons in the radicals are reported and discussed.     

A comprehensive study for selective removal of Cr(VI) by asymmetric imidazolium bromide salts as environmentally-friendly extractant

The study was to determine selective removal and recovery of Cr(VI) from acidic media by solvent extraction (SX) using asymmetric imidazolium-based room temperature imidazolium bromide salts (ARTILs) as the extractants. The relevant parameters on the extraction and the stripping of Cr(VI) were investigated to identify optimum conditions. The optimum conditions were determined as equilibration time 5 minutes, acid concentration and type 0.5?mol/L H₂SO₄, stirring speed 1200?rpm, extractant concentration and type 0.5?mol/L ARTIL5, phase ratio 2.0 and stripping reagent type, and concentration 2.0?mol/L NH₃. In optimum conditions, decyl substituted ARTIL was best in extraction process about 99.7% of extraction rate, whereas moderately hydrophobic pentyl substituted ARTIL was best in stripping process about 70.0% of stripping rate. Also, the optimized process was found as so selective toward Cr(VI) in the presence of the other metal ions with an environmental-friendly liquid–liquid–based SX method.