An improved skmplex algorithm for dealing with boundary conditions

Two existing and one new method for dealing with boundaries in simplex optimization are tested on 2-, 3-, and 5-parameter test functions, each subject to five different boundary conditions. The performance of the new method is shown to be the most consistent over all conditions.     

Towards benign syntheses of bipyridines: versatile approach to supramolecular building blocks

Chiral and achiral bipyridines are readily accessible via a solvent-free Michael addition involving solid NaOH, followed by treatment with ammonium acetate in acetic acid, as a ‘one pot’ more benign protocol, affording pure products in high yield, typically >80%.     

Simplex optimisation of inductively coupled plasmas

Meaningful comparisons of the analytical performances of different inductively coupled plasmas necessitate preliminary optimisation. The variable step-size simplex procedure is applied to optimise signal-to-background ratios for the five continuously variable operating parameters of a plasma, i.e. the power in the plasma, the observation height, and the injector, plasma and coolant gas flow rates. A series of univariate searches confirmed the results and also illustrated the importance of the various parameters. Results are presented for the manganese 257.6-nm ion line in both argon- and nitrogen-cooled plasmas and for the arsenic 228.8-nm atom line with argon coolant. Optimal power levels in these three cases were identified as 0.59, >1.2 and 0.57 kW, respectively.     

Cyclometallated platinum(II) complexes: oxidation to, and C-H activation by, platinum(IV)

A series of cyclometallated phenylpyridine platinum(II) complexes have been synthesised with a systematic variation in both the phenylpyridine and the ancillary ligand. Oxidation of one of the cyclometallated species leads to a number of isomeric platinum(IV) complexes, all of which eventually isomerize to a single compound. The route to these new compounds has been demonstrated to involve an initial slow oxidation followed by a rapid C-H activation to give doubly cyclometallated complexes. The solid state structures of a number of both the platinum(II) and the platinum(IV) species have been solved; many of the structures exhibited extended interactions that result in complex three dimensional packing.     

The application of an in vitro gastrointestinal extraction to assess the oral bioaccessibility of polycyclic aromatic hydrocarbons in soils from a former industrial site

The total and bioaccessible concentration of 16 polycyclic aromatic hydrocarbons (PAHs) in soil from a former industrial site was investigated. Typical total concentrations across the sampling sites ranged from 1.5 mg kg⁻¹ for acenaphthylene up to 243 mg kg⁻¹ for fluoranthene. The oral bioaccessibility of PAHs in soil was assessed using an in vitro gastrointestinal extraction (Fed Organic Estimation human Simulation Test, FOREhST method). The oral bioaccessibility data indicated that fluorene, phenanthrene, chrysene, indeno(1,2,3-cd)pyrene and dibenzo(a,h)anthracene had the highest % bioaccessible fraction (based on their upper 75th percentile values being >60%) while the other PAHs had lower % bioaccessible fractions (means ranging between 35 and 59%). Significantly lower bioaccessibilities were determined for naphthalene. With respect to method validation and inter-laboratory comparison, the total and bioaccessible concentrations of benzo(a)anthracene, benzo(b)anthracene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene and dibenzo(a,h)anthracene was compared to published data derived using the same samples. The total PAH concentrations at the site were compared with generic assessment criteria (GAC) using the residential land use scenario (with plant uptake at 6% soil organic matter). Concentrations of 7 of the PAHs investigated within the soils could lead to an unacceptable risk to human health at this site.     

Detection of some aliphatic saturated long-chain hydrocarbon derivatives by thin-layer chromatography

The aliphatic saturated long-chain alcohols, aldehydes, and diols were identified to a sensitivity of 50 μg from the parent hydrocarbons (C₁₀, C₁₂, C₁₄ and C₁₆) by thin-layer chromatography using “Silica Gel G”-coated pyrex chromatoplates for the fixed phase and ethyl acetate-n-hexane mixtures as the mobile phase. Identification of the developed spots was made by a modified charring technique employing ground glass pyrex plates coated with pyrosulfuric acid. Identification of the 1,n-dicarboxylic acid from the n-mono- or the 1,n-hydroxycarboxylic acid derived from the same parent hydrocarbon was effected in a mobile phase of 7:3:3 v/v ethanol- ammonia (conc.)-tetrahydrofuran. The indicator spray employed was an ethanolic solution of bromothymol blue. The spray was followed by exposure to ammonia vapor for intensification of the yellow acid spots.R_F value trends for the n-mono- and 1,n-bifunctional derivatives of the C₁₀ C₁₂, C₁₄ and C₁₆ aliphatic saturated hydrocarbons based on the—OH, —COOH and —CHO groups as the possible substituents are outlined.