Simultaneous determination of five polyether ionophores using liquid chromatography with one-step fluorescent derivatization

We present a selective method for simultaneous determination of five polyether ionophores such as salinomycin (SAL), monensin (MON), narasin (NAR), semduramicin (SEM) and lasalocid (LAS) in aquatic samples using a liquid chromatography with one-step fluorescent derivatization of 2-(4-hydrazinocarbonyl-phenyl) 4,5-diphenylimidazole (HCPI) and 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride hydrochloride (DIB-Cl). Fluorescent one-step derivatization for SAL, MON, NAR and SEM using HCPI and for LAS using DIB-Cl was monitored by an LC/fluorescence detector (E(x), 340 nm; E(m), 465 nm). Chromatographic separation was performed on a TSK-GEL ODS-120T (4.6 × 150 mm, 3 μm) column using a mobile phase of 0.1% formic acid in acetonitrile and 0.5 mM ammonium formate in water (70/30, v/v). The limits of detections were 0.01 μg/mL (50 pg) for LAS, 0.05 μg/mL (250 pg) for SAL, NAR and SEM, and 0.1 μg/mL (500 pg) for MON, respectively. The recoveries for water samples were indicated to be the range of 79.6 ± 6.4 - 99.0 ± 4.4% with associated precision values (between-day for 3 days) for repeatability. Based on solid-phase extraction, the limit of quantitation values indicated 0.1 ng/mL for SAL, MON, NAR and SEM, and 0.01 ng/mL for LAS in water samples.     

IR-extended photoluminescence mapping of single-wall and double-wall carbon nanotubes

A simple and efficient technique is described for measuring photoluminescence (PL) maps of carbon nanotubes (NTs) in the extended IR range (1-2.3 mum). It consists of preparing an NT/surfactant/gelatin film and measuring PL spectra using a combination of a tunable Ti-sapphire laser excitation and FTIR detection. This procedure has been applied to a wide range of single- and double-wall NTs unveiling chirality and diameter distributions that have so far been very difficult to measure. The problems associated with deducing these distributions are discussed by comparing absorption and PL mapping data for NT samples prepared under different conditions.     

Investigation of the structure of cellulose in LiCl/DMAc solution and its gelation behavior by small-angle X-ray scattering measurements

Cellulose gels were prepared from cellulose in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solution. When the cellulose concentration in the solution is above the one at which cellulose molecules overlap, cellulose gels were formed. While the gel prepared by the addition of water was turbid, the one prepared by the ion exchange was colorless, transparent, and optically anisotropic. In order to explain this gelation behavior of cellulose, small-angle X-ray scattering (SAXS) measurements of the cellulose solutions and the gels were performed. The SAXS profiles of the cellulose solutions and the gels suggested that the large-scale fluctuation of the molecular chain density in the solution can be the origin of the molecular aggregates formed in the gel. Furthermore, the differences in the structure of the gels at the macroscopic and the molecular level were discussed in terms of the phase separation and the molecular association.     

High yielding methyl esterification catalyzed by indium(III) chloride

The carboxylic acids are efficiently converted into the methyl esters in methanol using indium(III) chloride as the catalyst. This method is applicable for aromatic and aliphatic carboxyl moieties as well as amino acids in high yields.     

Light-induced transformation of alkylurea derivatives in aqueous TiO2 dispersion

The light-induced degradation of alkylurea derivatives under simulated solar irradiation has been investigated in aqueous solutions containing TiO(2) as a photocatalyst. Herein, we will focus on how the presence of one or more methyl (or ethyl) groups on urea modifies the kinetics of disappearance and influences both the ratio and the extent of the inorganic nitrogen formation caused by different degradation pathways. In the present work, we have elucidated a mechanism for the formation of transformation products of the alkyl derivatives by combining several analytical and spectroscopic procedures and the theoretical simulation of ab initio calculations. In all cases, N-demethylation represents only a secondary pathway, while the main transformation proceeds through an unexpected cyclization, involving (m)ethyl- and di(m)ethylureas with the formation of (methyl)amino-2,3-dihydro-1,2,4-oxadiazol-3-one as the principal intermediate of the reaction (with a yield of 60 %). This behaviour is rather unexpected and in contrast with the typical photocatalyzed transformation pathways, which proceed through the formation of more simple structures.     

Iron-based layered superconductor: LaOFeP

We report superconductivity in an iron-based layered oxy-pnictide LaOFeP. LaOFeP is composed of an alternate stack of lanthanum oxide (La3+O2-) and iron pnictide (Fe2+P3-) layers. Magnetic and electrical resistivity measurements verify the occurrence of the superconducting transition at approximately 4 K.     

Synthesis of alpha-amino acid precursors directly from aldehydes using masked acyl cyanide reagents and N,O-dialkylated hydroxylamines

A synthetic methodology for the synthesis of alpha-amino acid precursors directly from the corresponding aldehydes using N,O-dialkylated hydroxylamines and masked acyl cyanide (MAC) reagents was developed. The one-pot reaction can be carried out under mild conditions and without a separate purification step of the imino species. The method was applied to the synthesis of optically pure (+)-4-methylphenylglycine and the derivatives by using an Abiko-Masamune's tricyclic 1,2-oxazolidine as the chiral auxiliary.     

Electronic property of SrFe2As2 under high pressure studied by 57Fe M?ssbauer spectroscopy

An illustrious complex [Fe(ptz)₆](BF₄)₂ (ptz = 1-propyl-tetrazole) (1) which was produced in the form of submicron crystals and thin film on Allium cepa membrane was probed by ⁵⁷Fe Mossbauer spectroscopy in order to follow its intrinsic spin crossover. In addition to a weak signal that corresponds to neat SCO compound significant amount of other iron compounds are found that could have morphed from 1 due to specific host-guest interaction on the lipid-bilayer of bio-membrane. Further complimentary information about biogenic role of membrane, was obtained from variable temperature Mossbauer spectroscopy on a ~5% enriched [⁵⁷Fe(H₂O)₆](BF₄)₂ salt on this membrane.     

Monte Carlo simulations of the exchange kinetics of polymers adsorbed on a solid surface

The exchange kinetics of polymers adsorbing on a solid surface is extensively studied by dynamic Monte Carlo simulations. A model employed simulates a semidilute polymer solution placed in contact with a solid surface that attracts polymer segments by the adsorption interaction (χ_s). The exchange process of polymer chains, between the solution and the adsorbed polymer layer, is examined under various conditions. The exchange kinetics shows two characteristic regimes with increasing chain length. One is the diffusion‐controlled regime found with a small χ_s , and the other the detachment‐controlled regime with a large χ_s . These two regimes are well described by a kinetic theory. Various dynamic quantities show that the diffusion‐controlled regime is not due to sluggish dynamics near the surface, but rather to bulk diffusion of chains. The diffusion‐controlled regime found in this study is considered to appear at the high temperature limit.