A simple and rapid method for determination of boron in fast breeder reactor components

The present paper describes a new analytical method developed for direct determination of boron in steels using radio frequency glow discharge optical emission spectrometer. “Single parameter alternative method” technique has been used to optimize the various experimental conditions of glow discharge plasma such as forward power, gas pressure inside plasma chamber, pre-integration time, and integration time. Different emission lines for boron were studied and inter element interference effect is also discussed in the paper. A complete statistical analysis has been done to validate the developed method. A RSD of less than ±5% is achieved for boron in the range of 0.0010–0.020% in Steels using this method.     

Mechanism of Fenpropathrin Resistance in Red Spider Mite, <Emphasis Type="Italic">Oligonychus coffeae</Emphasis> (Acarina: Tetranychidae), Infesting Tea [<Emphasis Type="Italic">Camellia sinensis</Emphasis> L. (O. Kuntze)]

Red spider mite (RSM), Oligonychus coffeae (Nietner) (Acarina: Tetranychidae), has gained special attention in view of their widespread occurrence as a pest on tea [Camellia sinensis L. (O. Kuntze)]. The development of acaricide (fenpropathrin) resistance has been screened in field populations (FPs) of RSMs from different tea-growing regions of south India and compared with a laboratory-susceptible population (SP) based on toxicity bioassay, detoxifying enzyme activities, analysis of acetylcholine esterase gene (AChE, 2064 bp), and their expression pattern using semiquantitative RT-PCR. The increased resistance ratio (RR, 1.39 to 2.13) in LC₅₀ of fenpropathrin observed in field populations of RSM provides a baseline for screening the development of resistance to fenpropathrin. This resistance developed due to hyperexpression of detoxifying enzymes, i.e., esterase (RR of 1.43 to 2.53) and glutathione S-transferase (RR of 1.11 to 1.86), and overexpression of AChE gene at 1.4 to 2.7-fold. These results necessitate molecular studies and warrant the continuous monitoring of acaricide susceptibility and resistance pattern in order to analyze the usefulness of AChE gene as target for developing alternate pest control strategies and management of pesticide resistance in tea ecosystem.     

Enantiospecific synthesis of ABC-ring system of A-nor and abeo 4(3→2) tetra and pentacyclic triterpenes

Enantiospecific synthesis of ABC-ring systems of A-nor and abeo 4(3→2) tetra and pentacyclic triterpenes has been accomplished starting from the readily available monoterpene (R)-carvone. (R)-Carvone was used as the B-ring of the target molecules. A lithium-liquid ammonia mediated cyclisation of δ,?-unsaturated ester was employed for the cyclopentannulation at the C-5 and C-6 carbons of carvone and an RCM reaction was employed for the cyclohexannulation to generate the ABC-ring system of A-nor tetra and pentacyclic triterpenes. The strategy has been extended for the synthesis of the ABC-ring system of abeo 4(3→2) tetra and pentacyclic triterpenes.     

Allosteric effect of the first lead ion on stepwise extraction of the second lead ion with p-t-butylcalix[5]arene pentacarboxylic acid derivative

A calix[5]arene-based solvent extraction reagent displaying very high selectivity for lead has been prepared, one molecule of which extracts two lead ions in a stepwise manner. The first Pb²⁺ ion is bound to five phenoxy oxygen atoms inside the calixarene cavity due to which the ligand undergoes conformational freezing in stable cone conformer. This causes positive allosteric effect for co-extraction of the second lead ion due to the aggregation of functional groups.     

DMAP-catalyzed synthesis of 2-oxazolidinones from corresponding halohydrins using KOCN/DMF

We report facile and simple synthesis of a variety of 2-oxazolidinones from the corresponding halohydrins by reaction with KOCN in DMF catalyzed by DMAP. DMAP and temperature play key roles in enriching the yield of 2-oxazolidinones. A few examples in this Letter are applicable to pharmaceutically important processes.     

Single step modification of copper electrode for the highly sensitive and selective non-enzymatic determination of glucose

A non-enzymatic sensor was developed for the determination of glucose in alkaline medium by anodisation of copper in sodium potassium tartrate solution. The morphology of the modified copper electrode was studied by scanning electron microscopy, and its electrochemical behavior by cyclic voltammetry and electrochemical impedance spectroscopy. The electrode enables direct electrocatalytic oxidation of glucose on a CuO/Cu electrode at 0.7 V in 0.1 M sodium hydroxide. At this potential, the sensor is highly selective to glucose even in the presence of ascorbic acid, uric acid, or dopamine which are common interfering species. The sensor displays a sensitivity of 761.9 μA mM^?1 cm^?2, a linear detection range from 2 μM to 20 mM, a response time of <1 s, and a detection limit of 1 μM (S/N = 3). It was tested for determination of glucose level in blood serum.     

Quantitative estimation of riluzole in human plasma by LC-ESI-MS/MS and its application to a bioequivalence study

A novel simple, sensitive, selective, and rapid high-performance liquid chromatography coupled with tandem mass spectrometry method was developed and validated for quantification of riluzole in human plasma. The chromatography was performed by using a Zorbax-SB-C18 (4.6 × 75 mm, 3.5 μm) column , isocratic mobile phase 0.1% formic acid/acetonitrile (10:90 v/v), and an isotope-labeled internal standard (IS), [¹³C,¹⁵N₂]riluzole. The extraction of drug and internal standard was performed by liquid–liquid extraction and analyzed by MS in the multiple reaction monitoring (MRM) mode using the respective [M+H]⁺ ions, m/z 235.0/165.9 for riluzole and m/z 238.1/169.0 for the IS. The calibration curve was linear over the concentration range 0.5–500.0 ng/ml for riluzole in human plasma. The limit of quantification (LOQ) was demonstrated at 0.5 ng/ml. The within-batch and between-batch precision were 0.6–2.3% and 1.4–5.7%, and accuracy was 97.1–101.1% and 98.8–101.2% for riluzole respectively. Drug and IS were eluted within 3.0 min. The validated method was successfully applied in a bioequivalence study of riluzole in human plasma.     

Differentiation of Boc‐protected α,δ‐/δ,α‐ and β,δ‐/δ,β‐hybrid peptide positional isomers by electrospray ionization tandem mass spectrometry

Two new series of Boc‐N‐α,δ‐/δ,α‐ and β,δ‐/δ,β‐hybrid peptides containing repeats of L ‐Ala‐δ⁵‐Caa/δ⁵‐Caa‐L ‐Ala and β³‐Caa‐δ⁵‐Caa/δ⁵‐Caa‐β³‐Caa (L ‐Ala = L ‐alanine, Caa = C‐linked carbo amino acid derived from D ‐xylose) have been differentiated by both positive and negative ion electrospray ionization (ESI) ion trap tandem mass spectrometry (MS/MS). MSⁿ spectra of protonated isomeric peptides produce characteristic fragmentation involving the peptide backbone, the Boc‐group, and the side chain. The dipeptide positional isomers are differentiated by the collision‐induced dissociation (CID) of the protonated peptides. The loss of 2‐methylprop‐1‐ene is more pronounced for Boc‐NH‐L ‐Ala‐δ‐Caa‐OCH₃ (1), whereas it is totally absent for its positional isomer Boc‐NH‐δ‐Caa‐L ‐Ala‐OCH₃ (7), instead it shows significant loss of t‐butanol. On the other hand, second isomeric pair shows significant loss of t‐butanol and loss of acetone for Boc‐NH‐δ‐Caa‐β‐Caa‐OCH₃ (18), whereas these are insignificant for its positional isomer Boc‐NH‐β‐Caa‐δ‐Caa‐OCH₃ (13). The tetra‐ and hexapeptide positional isomers also show significant differences in MS² and MS³ CID spectra. It is observed that ‘b’ ions are abundant when oxazolone structures are formed through five‐membered cyclic transition state and cyclization process for larger ‘b’ ions led to its insignificant abundance. However, b₁⁺ ion is formed in case of δ,α‐dipeptide that may have a six‐membered substituted piperidone ion structure. Furthermore, ESI negative ion MS/MS has also been found to be useful for differentiating these isomeric peptide acids. Thus, the results of MS/MS of pairs of di‐, tetra‐, and hexapeptide positional isomers provide peptide sequencing information and distinguish the positional isomers. Copyright © 2010 John Wiley & Sons, Ltd.     

2,6‐Bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine and its octahedral copper complex

In the tridentate ligand 2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine, C₂₃H₁₉N₇, both sets of triazole N atoms are anti with respect to the pyridine N atom, while in the copper complex aqua[2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine](pyridine)(tetrafluoroborato)copper(II) tetrafluoroborate, [Cu(BF₄)(C₅H₅N)(C₂₃H₁₉N₇)(H₂O)]BF₄, the triazole N atoms are in the syn–syn conformation. The coordination of the Cu^II atom is distorted octahedral. The ligand structure is stabilized through intermolecular C—H...N interactions, while the crystal structure of the Cu complex is stabilized through water‐ and BF₄‐mediated hydrogen bonds. Photoluminiscence studies of the ligand and complex show that the ligand is fluorescent due to triazole–pyridine conjugation, but that the fluorescence is quenched on complexation.     

A Neutral Four-Coordinate Mononuclear Cobalt(II) Complex with Biphenyl Appended N-Bidendate Ligand: Synthesis, Structure and Spectral Properties

Abstract  

A mononuclear cobalt(II) complex [Co(BP)(Cl₂)], 1 with a new N,N-bidentate ligand, BP ([N,N-(1,1′-biphenyl-2,2′-dimethylene)]-2-aminomethyl) pyridine) was synthesized and characterized by elemental analysis, UV–Vis, paramagnetic NMR, magnetic moment and single crystal XRD. The air and moisture stable Co(II) title complex is a 15 electron species which crystallizes in the monoclinic space group P2₁/n with cell dimensions a = 10.406(3), b = 12.873(4), c = 13.859(7) ?, β = 96.30(3)˚ and Z = 4. The cobalt atom has distorted tetrahedral (td) geometry with coordination provided by an amine and pyridyl nitrogen donors of BP and two terminal chloride ions. The packing is stabilized through C–H···π and van der Waals interactions.