Effects of chain length and heat treatment on the nanotribology of alkylsilane monolayers self-assembled on a rough aluminum surface

The conformational order of alkylsilane monolayers self-assembled on a rough aluminum surface is affected by the molecular chain length and the thermal history of the sample. These monolayers have been characterized by grazing angle FTIR spectroscopy. Tribological mechanisms were explored using initial molecular conformation order, sliding distance, normal load, and substrate compliance as experimental variables. Results indicate that the initial conformational disorder of the molecules determines the level of friction at the commencement of sliding. Adverse changes in dynamic friction and monolayer life during sliding are not thermally induced but are related to substrate roughness and local plasticity. Plastic deformation reduces the spatial density of the alkylsilane monolayer and is accentuated by an increase in the normal load.     

RP-LC Determination of the cis-Isomer of Glimepiride in a Bulk Drug Substance

A rapid reversed-phase high-performance liquid chromatographic procedure is developed and validated for the resolution of the cis-isomer of 1-[[p-[2-(3-ethyl-4-methyl-2-oxo-3-pyrroline-1-carboxamido) ethyl] phenyl] sulfonyl]-3-(trans-4-methylcyclohexyl) urea, a dopamine agonist in bulk drugs. The cis-isomer and glimepiride were baseline resolved on a Waters Symmetry column (50 × 4.6 mm, 3.5 μm) using a mobile phase system containing water: tetrahydrofuran (75:25; v/v. The chromatographic resolutions between cis-isomer and glimepiride were found to be greater than two. The developed method was extensively validated and proved to be robust. The limit of detection and the limit of quantification of cis-isomer were 500 and 1,500 ng mL⁻¹, respectively, for 10 μL injection volume. The percentage recovery of the cis-isomer ranged from 97.3 to 102.0 in bulk drug samples of glimepiride. Glimepiride sample solution and mobile phase were found to be stable for at least 48 h. The proposed method was found to be suitable and accurate for the quantitative determination of the cis-isomer in bulk drugs.     

Determination of chromium in aquatic environment by substoichiometric thermal neutron activation analysis

Chromium has been determined in environmental samples. The method described here involves the irradiation of environmental samples and a g quantity of standard with thermal neutrons at the self-serve position in the CIRUS reactor, followed by dissolution of the sample and standard in the presence of a milligram amount of carrier. Both the sample and the standard are subjected to substoichiometric extraction under controlled experimental conditions with alizarin into cyclohexane. An aliquot of the organic phase was counted on a gamma-ray spectrometer. The concentration of Cr in water samples from Bombay and Karad City, and the accuracy, precision and sensitivity of the method are discussed.     

Organoboranes—34 : General synthesis of chiral boronic and borinic esters via asymmetric hydroboration-displacement. carbenoidation of chiral borinic esters to acyclic ketones of high enantiomeric purities

Asymmetric hydroboration of appropriate alkenes with diisopinocampheylborane (Ipc₂BH) or monoisopinocampheylborane (IpcBH₂) produces intermediates that readily eliminate α-pinene on treat- ment with acetaldehyde, providing a direct, convenient route to chiral boronic esters of high enantiomeric purities. Mixed chiral trialkylboranes, readily prepared by stepwise hydroboration of appropriate alkenes with IpcBH₂, eliminate α-pinene on treatment with acetaldehyde under very mild conditions. The procedure makes readily available chiral borinic esters of high enantiomeric purities. The synthetic utility of chiral borinic esters is demonstrated by converting them into acyclic ketones including an alarm pheromone of the ant Monica mutica.     

Increased paraoxon detection by acetylcholinesterase inactivation with ionic liquid additives

This is the first study using ionic liquids (ILs) as additive in the aqueous solvent medium for detection of paraoxon by acetylcholinesterase inhibition method. A systematic comparison of various ILs with organic solvents has been made. The aqueous buffer solution containing ionic liquid ethylpyridinium hexafluorophosphate [EtPy]⁺[PF₆]⁻ has been found to give the best results. The inhibition kinetic follows the first order model. Ionic liquids modified aqueous solutions show the potential to provide a promising and effective medium in detection of paraoxon with acetylcholinesterase.     

A general method for the deoxygenation of aromatic N-oxides using RuCl3·xH2O

An efficient, simple and selective method for the deoxygenation of aromatic N-oxides, such as N-arylnitrones, azoxybenzenes, N-heteroarene N-oxides using ruthenium(III) chloride to afford deoxygenated products in excellent yields, is described.     

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.     

High-throughput ribozyme-based assays for detection of viral nucleic acids

Many reports have suggested that target-activated ribozymes hold potential value as detection reagents. We show that a "half"-ribozyme ligase is activated similarly by three unstructured oligoribonucleotides representing the major sequence variants of a hepatitis C virus 5'-untranslated region (5'-UTR) target and by a structured RNA corresponding to the entire 5'-UTR. Half-ribozyme ligation product was detected both in an ELISA-like assay and in an optical immunoassay through the use of hapten-carrying substrate RNAs. Both assay formats afford a limit of detection of approximately 1 x 10(6) HCV molecules (1.6 attomol, 330 fM), a sensitivity which compares favorably to that provided by standard immunoassays. These data suggest that target-activated ribozyme systems are a viable approach for the sensitive detection of viral nucleic acids using high-throughput platforms.     

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.