Optimisation of solvent desorption conditions for chemical warfare agent and simulant compounds from Porapak Q using experimental design. I. Methyl salicylate and di(propylene glycol) monomethyl ether

Factorial design (FD) was applied in order to develop an optimised method for the detection of chemical warfare (CW) agent simulant compounds on Porapak Q. Application of FD allowed study of the adsorption/desorption mechanism of analytes. Di(propylene glycol) monomethyl ether (DPM) and methyl salicylate (MS) were selected for study as both compounds are employed in agent simulation trials but are currently analysed by different methods. An analytical method for simultaneous determination of both compounds was developed using solvent desorption. The optimised method identified non-polar interactions as the primary adsorption/desorption mechanism. Steel tubes were shown to be more suited for sampling of simulants, due to lower variability in recovery compared to glass tubes. Atmospheric detection limits for both simulants were estimated to be 0.2 mg m(-3) allowing the trace analysis of these compounds by gas chromatography with flame ionisation detection (GC-FID).     

The Laser Raman Spectrum of Polyethylene Glycol Dimethacrylate)

Abstract

The laser Raman spectrum of poly(ethylene glycol dimethacrylate) (PEGDMA) with depolarization data is presented. Qualitative vibrational assignments of the observed bands are proposed using the empirical method of characteristic group frequencies.     

Effect of counter-ion on the thermotropic liquid crystal behaviour of bis(alkyl)-tris(imidazolium salt) compounds

Recently, new thermotropic ionic liquid crystals (LCs) with a hexyl-linked tris(imidazolium bromide) core and two terminal alkyl chains were synthesised and characterised. To explore the effect of different counter-ions on the LC behaviour of this system, derivatives with BF₄^? and Tf₂N^? counter-ions were prepared and analysed. Five of the BF₄^? derivatives were found to exhibit thermotropic LC behaviour. The 12-, 14- and 16-carbon tail BF₄^? compounds form SmA phases. The 18- and 20-carbon tail homologues form what appears to be a smectic phase but are weakly mesogenic and harder to characterise. Only two of the Tf₂N^? derivatives exhibited mesogenic behaviour. The 18-carbon tail Tf₂N^? compound forms an as-yet unidentified, highly periodic smectic phase with positional order while the 20-carbon tail homologue forms a periodic SmA phase. The Tf₂N^? mesogens have much lower clearing points even though their LC phases have more order than the Br^? and BF₄^? mesogens. X-ray diffraction showed that these mesogens have different amounts of tail interdigitation between the smectic layers depending on the counter-ion present. Atomistic molecular dynamics simulations indicated that counter-ion size plays an important role in defining the density of the ionic region, which in turn affects the amount of interdigitation in the smectic phases.     

Replacement of Poly(vinyl pyrrolidone) by Thiols: A Systematic Study of Ag Nanocube Functionalization by Surface-Enhanced Raman Scattering

In this work, we used surface-enhanced Raman scattering (SERS) to monitor the replacement of poly(vinyl pyrrolidone) (PVP) on Ag nanocubes by cysteamine, thiol-terminated PEG, and benzenedithiol. PVP is widely used as a colloidal stabilizer and capping agent to control the shape of Ag (as well as many other noble metals) nanocrystals during synthesis, and to stabilize the final colloidal suspension. However, the surface chemistry of Ag nanocrystals often needs to be tailored for specific applications, so the PVP coating must be removed and/or replaced by other ligands. By monitoring the signature peak from the carbonyl groups of PVP, we show, for the first time, that the PVP adsorbed on the surface of Ag nanocubes was completely replaced by the thiol molecules at room temperature over the course of a few hours. We observed the same trend no matter if the Ag nanocubes were suspended in an aqueous solution of the thiol or supported on a silicon substrate and then immersed in the thiol solution.     

Formation of 4-N-Arylamino-1-butanol Derivatives from Aromatic Nitro Compounds via a Novel Palladium-Catalyzed Tetrahydrofuran Ring-Opening Reaction

Abstract

4-N-Arylamino-1-butanol derivatives are produced via a palladium-catalyzed tetrahydrofuran ring-opening reaction. This reaction occurs during the reduction of aromatic nitro groups with polymethylhydrosiloxane (PMHS) and potassium fluoride in the presence of hydrogen peroxide. This represents a novel route for the synthesis of 4-N-arylamino-1-butanols.     

Monitoring of progestins: Development of immunochemical methods for purification and detection of levonorgestrel

A polyclonal antibody (Ab) for the progestin levonorgestrel (LNG) was generated, and immunochemical assays for its detection, clean-up and concentration were developed. A highly specific microplate diagnostic assay for the detection of LNG was developed that used the enzyme linked immunosorbent assay (ELISA) method. The LNG ELISA developed was sensitive and reproducible; it exhibited I₅₀ and I₂₀ values of 3.3 ± 1.8 ng mL⁻¹ and 0.6 ± 0.4 ng mL⁻¹, respectively, and the Abs did not cross react with any of the tested steroid hormones. The above Abs were used to develop a sol-gel-based immunoaffinity purification (IAP) method for concentration and clean-up of LNG that is compatible with subsequent immunochemical or instrumental chemical analytical procedures, such as liquid chromatography followed by mass spectrometry (LC-MS/MS). Development of the columns included successful entrapment of Abs within a tetramethoxysilane (TMOS)-based SiO₂ polymer network. The Abs could bind the free analyte from solution, and the bound analyte could be easily eluted from the sol-gel matrix at high recoveries. The Ab selectivity towards the antigen was high, in both ELISA and the sol-gel columns, but the entrapped Abs cross-reacted with two other steroid hormones - ethynylestradiol (EE2) and nortestosterone (NT) - which share similar epitopes with LNG, despite the lack of cross reactivity in the ELISA. The validity of the method was investigated by LC-MS/MS and a good analytical correlation was obtained.     

Lattice Poisson-Boltzmann simulations of electro-osmotic flows in microchannels

This paper presents the numerical results of electro-osmotic flows in micro- and nanofluidics using a lattice Poisson-Boltzmann method (LPBM) which combines a potential evolution method on discrete lattices to solve the nonlinear Poisson equation (lattice Poisson method) with a density evolution method on discrete lattices to solve the Boltzmann-BGK equation (lattice Boltzmann method). In an electrically driven osmotic flow field, the flow velocity increases with both the external electrical field strength and the surface zeta potential for flows in a homogeneous channel. However, for a given electrical field strength and zeta potential, electrically driven flows have an optimal ionic concentration and an optimum width that maximize the flow velocity. For pressure-driven flows, the electro-viscosity effect increases with the surface zeta potential, but has an ionic concentration that yields the largest electro-viscosity effect. The zeta potential arrangement has little effect on the electro-viscosity for heterogeneous channels. For flows driven by both an electrical force and a pressure gradient, various zeta potential arrangements were considered for maximize the mixing enhancement with a less energy dissipation.     

Photoinduced 1,4-additions of indoles to enones

[reaction: see text] A photoinduced procedure for the 1,4-addition of indoles to enones is described. This reaction occurs with modest to excellent yield for cyclic and some acyclic enones. This reaction is experimentally simple, requiring only irradiation (UVA lamps, ca. 350 nm) of the reagents in a CH2Cl2 solution at room temperature, and avoids the necessity to use a Lewis acid. An important solvent effect was noticed, with CH2Cl2 and CHCl3 being the optimal solvents. Various substituents are tolerated on the indole moiety and an electronic trend was noticed, as electron-withdrawing groups can suppress this reaction. A mechanism involving single electron transfer between the enone triplet excited state and the indole is proposed and accounts for all experimental observations.