Effect of shearing stress on the radial heterogeneity and chromatographic performance of styrene-based polymerised high internal phase emulsions prepared in capillary format

Poly(styrene-co-divinylbenzene) monoliths were prepared from the polymerisation of water-in-monomer high internal phase emulsions consisting of a 90 vol% internal phase and stabilised by the non-ionic surfactant Span 80®. The materials were prepared in capillary housings of various internal diameters ranging from 150 μm to 540 μm by simply passing the emulsion through the capillaries. When low shear (300 rpm) was used for emulsification, the droplet and resulting void size distributions were observed to shift towards lower values when the emulsions were forced through capillaries of internal diameter less than 540 μm and all columns exhibited significant radial heterogeneity. When high shear was employed (14 000 rpm) the resulting emulsions preserved their structure when forced through these capillaries and possessed narrower void size distributions with no obvious radial heterogeneity observed upon curing. This resulted in significantly improved chromatographic performance for the separation of a standard mixture of proteins when compared to the materials prepared under low shear

Biocompatible functionalisation of nanoclays for improved environmental remediation

Among the wide range of materials used for remediating environmental contaminants, modified and functionalised nanoclays show particular promise as advanced sorbents, improved dispersants, or biodegradation enhancers. However, many chemically modified nanoclay materials are incompatible with living organisms when they are used in natural systems with detrimental implications for ecosystem recovery. Here we critically review the pros and cons of functionalised nanoclays and provide new perspectives on the synthesis of environmentally friendly varieties. Particular focus is given to finding alternatives to conventional surfactants used in modified nanoclay products, and to exploring strategies in synthesising nanoclay-supported metal and metal oxide nanoparticles. A large number of promising nanoclay-based sorbents are yet to satisfy environmental biocompatibility in situ but opportunities are there to tailor them to produce "biocompatible" or regenerative/reusable materials

Identification of inorganic improvised explosive devices by analysis of postblast residues using portable capillary electrophoresis instrumentation and indirect photometric detection with a light-emitting diode

A commercial portable capillary electrophoresis (CE) instrument has been used to separate inorganic anions and cations found in postblast residues from improvised explosive devices (IEDs) of the type used frequently in terrorism attacks. The purpose of this analysis was to identify the type of explosive used. The CE instrument was modified for use with an in-house miniaturized light-emitting diode (LED) detector to enable sensitive indirect photometric detection to be employed for the detection of 15 anions (acetate, benzoate, carbonate, chlorate, chloride, chlorite, cyanate, fluoride, nitrate, nitrite, perchlorate, phosphate, sulfate, thiocyanate, thiosulfate) and 12 cations (ammonium, monomethylammonium, ethylammonium, potassium, sodium, barium, strontium, magnesium, manganese, calcium, zinc, lead) as the target analytes. These ions are known to be present in postblast residues from inorganic IEDs constructed from ammonium nitrate/fuel oil mixtures, black powder, and chlorate/perchlorate/sugar mixtures. For the analysis of cations, a blue LED (470 nm) was used in conjunction with the highly absorbing cationic dye, chrysoidine (absorption maximum at 453 nm). A nonaqueous background electrolyte comprising 10 mM chrysoidine in methanol was found to give greatly improved baseline stability in comparison to aqueous electrolytes due to the increased solubility of chrysoidine and its decreased adsorption onto the capillary wall. Glacial acetic acid (0.7% v/v) was added to ensure chrysoidine was protonated and to enhance separation selectivity by means of complexation with transition metal ions. The 12 target cations were separated in less than 9.5 min with detection limits of 0.11-2.30 mg/L (calculated at a signal-to-noise ratio of 3). The anions separation system utilized a UV LED (370 nm) in conjunction with an aqueous chromate electrolyte (absorption maximum at 371 nm) consisting of 10 mM chromium(VI) oxide and 10 mM sodium chromate, buffered with 40 mM tris(hydroxymethyl)aminomethane at pH 8.05. All 15 target anions were baseline separated in less than 9 min with limits of detection ranging from 0.24 to 1.15 mg/L (calculated at a signal-to-noise ratio of 3). Use of the portable instrumentation in the field was demonstrated by analyzing postblast residues in a mobile laboratory immediately after detonation of the explosive devices. Profiling the ionic composition of the inorganic IEDs allowed identification of the chemicals used in their construction