Solvent Solubility Testing of Cosmetics-Relevant Chemicals: Methodology and Correlation of Water Solubility to In Silico Predictions

Aqueous solubility is one of the main physicochemical parameters used to assess skin absorption. As solvents have great impact on skin absorption, knowledge of chemical solubility in appropriate solvents is key to correlate in vitro skin penetration with in vivo outcomes. For example, acetone:olive oil, ethanol and dimethyl sulfoxide are all relevant to in vitro and in vivo assays. Solubility information is also needed to identify the optimal solvent for skin penetration assays. Therefore, we have measured the solubilities of 54 chemicals related to cosmetics and the reference controls for skin sensitization and genotoxicity, in five different solvents: water, DMSO, ethanol, acetone:olive oil (4:1), 5% ethanol in 0.1 mol·L^?1 phosphate buffered saline. The solubility protocol resulted in highly reproducible values, with greatest variability for poorly soluble chemicals, especially those in 0.1 mol·L^?1 PBS, which may be due to the high salt content. There was good agreement between experimental and literature values for water solubility (mean difference < twofold). A better correlation of experimental values with in silico predictions was obtained using ACD/Labs software (mean difference < fourfold, R² = 0.64) than WSKOW from EpiSuite (mean difference < eightfold, R² = 0.48). Chemicals with a log₁₀P > 2 generally exhibited a poor solubility in water but a much higher solubility in acetone:olive oil, ethanol and DMSO. These five solvents include pH effects, acceptor and donor hydrogen bonding and non-polar interactions. Thus, the solubility profile across these different solvents would help to characterize the chemicals related to their cutaneous absorption with different vehicles and their toxicity assessment.     

Mixed-mode and reversed-phase liquid chromatography-tandem mass spectrometry methodologies to study composition and base hydrolysis of polysorbate 20 and 80

Polysorbate 20 (polyoxyethylenesorbitan monolaurate) and polysorbate 80 (polyoxyethylenesorbitan monooleate) used in protein drug formulations are complex mixtures that have been difficult to characterize. Here, two HPLC methods are used with evaporative light scattering detection (ELSD) and mass spectrometry (MS) to characterize polysorbate from commercial vendors. The first HPLC method used a mixed-mode stationary phase (Waters Oasis MAX, mixed-mode anion exchange and reversed-phase sorbent) with a step gradient to quantify both the total polyoxyethylene sorbitan ester and polyoxyethylene sorbitan (POE sorbitan, a non-surfactant) in polysorbate. The results indicated POE sorbitan was present from 16.0 to 27.6 and 11.1 to 14.5% (w/w) in polysorbate 20 and 80, respectively. The second HPLC method used a reversed-phase stationary phase (Zorbax SB-300 C(8)) with a shallow gradient to separate, identify, and quantify the multiple ester species present in polysorbate. For all lots of polysorbate 20 analyzed, only 18-23% of the material was the expected structure, polyoxyethylenesorbitan monolaurate. Up to 40% and 70% (w/w) di- and triesters were found in polysorbate 20 and polysorbate 80 respectively. Likewise, polyoxyethylenesorbitan monooleate accounted for only 20% of polysorbate 80. A variability of 3-5% was observed for each ester species between multiple lots of polysorbate 20. The reversed-phase method was then used to determine the rate of hydrolysis for each polyoxyethylene sorbitan ester of polysorbate 20 in basic solution at room temperature. Increasing rates of hydrolysis were observed with decreasing aliphatic chain lengths in polysorbate 20.     

Preliminary fingerprinting of Athabasca oil sands polar organics in environmental samples using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

There is a growing need to develop analytical methods that can distinguish compounds found within industrially derived oil sands process water (OSPW) from those derived from natural weathering of oil sands deposits. This is a difficult challenge as possible leakage beyond tailings pond containments will probably be in the form of mixtures of water-soluble organics that may be similar to those leaching naturally into aquatic environments. We have evaluated the potential of negative ion electrospray ionization high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) for comparing oil sands polar organics from tailing ponds, interceptor wells, groundwater, river and lake surface waters. Principal component analysis was performed for all species observed. which included the O(2) class (often assumed to be monocarbxoylic naphthenic acids) along with a wide range of other species including humic substances in the river and lake samples: O(n) where n=1-16; NO(n) and N(2)O(n) where n=1-13; and O(n)S and O(n)S(2) where n=1-10 and 1-8, respectively. A broad range of species was investigated because classical naphthenic acids can be a small fraction of the 'organics' detected in the polar fraction of OSPW, river water and groundwater. Aquatic toxicity and environmental chemistry are attributed to the total organics (not only the classical naphthenic acids). The distributions of the oil sands polar organics, particularly the sulfur-containing species, O(n)S and O(n)S(2), may have potential for distinguishing sources of OSPW. The ratios of species containing O(n) along with nitrogen-containing species: NO(n), and N(2)O(n), were useful for differentiating organic components derived from OSPW from those found in river and lake waters. Further application of the FTICRMS technique for a diverse range of OSPW of varying ages and composition, as well as the surrounding groundwater wells, may be critical in assessing whether leakage from industrial sources to natural waters is occurring.     

Rapid Synthesis of Porous Honeycomb Cu/Pd through a Hydrogen‐Bubble Templating Method

A rapid electrochemical method based on using a clean hydrogen‐bubble template to form a bimetallic porous honeycomb Cu/Pd structure has been investigated. The addition of palladium salt to a copper‐plating bath under conditions of vigorous hydrogen evolution was found to influence the pore size and bulk concentration of copper and palladium in the honeycomb bimetallic structure. The surface was characterised by X‐ray photoelectron spectroscopy, which revealed that the surface of honeycomb Cu/Pd was found to be rich with a Cu/Pd alloy. The inclusion of palladium in the bimetallic structure not only influenced the pore size, but also modified the dendritic nature of the internal wall structure of the parent copper material into small nanometre‐sized crystallites. The chemical composition of the bimetallic structure and substantial morphology changes were found to significantly influence the surface‐enhanced Raman spectroscopic response for immobilised rhodamine B and the hydrogen‐evolution reaction. The ability to create free‐standing films of this honeycomb material may also have many advantages in the areas of gas‐ and liquid‐phase heterogeneous catalysis.     

Diastereoselective alkylation reactions of 1-methylcyclohexa-2,5-diene-1-carboxylic acid

The deprotonation and alkylation of 1-methylcyclohexa-2,5-diene-1-carboxylic acid has been investigated under a range of conditions. In all cases, the formation of compounds 14 was found to be completely stereoselective, although compound 14c was formed as an impurity when alkyl iodides were used as electrophiles, and doubly-alkylated compounds 17 were formed in some cases when alkyl bromides were used.     

Continuous Cohomology of Permutation Groups on Profinite Modules

ABSTRACT

Model theorists have made use of low-dimensional continuous cohomology of infinite permutation groups on profinite modules, see Ahlbrandt and Ziegler (1991 Ahlbrandt , G. , Ziegler , M. ( 1991 ). What's so special about (?/4?)^ω? Archive for Math. Logic 31 : 115 – 132 . [CSA] [Crossref] , [Google Scholar]), Evans (1997b Evans , D. M. ( 1997b ). Computation of first cohomology groups of finite covers . J. Algebra 193 : 214 – 238 . [CSA] [CROSSREF] [Crossref], [Web of Science ®] , [Google Scholar]), Evans et al. (1997 Evans , D. M. , Ivanov , A. A. , Macpherson , H. D. ( 1997 ). Finite covers . In: Evans , D. M. , ed. Model Theory of Groups and Automorphism Groups . London Mathematical Society Lecture Notes 244 . Cambridge : Cambridge Univ Press , pp. 1 – 72 .[Crossref] , [Google Scholar]), and Hodges and Pillay (1994 Hodges , W. , Pillay , A. ( 1994 ). Cohomology of structures and some problems of Ahlbrandt and Ziegler . J. London Math. Soc. 50 ( 2 ): 1 – 16 . [CSA] [Crossref] , [Google Scholar]), for example. We expand the module category in order to widen the cohomological toolkit. For an important class of groups we use these tools to establish criteria for finiteness of cohomology.     

Sensitive voltammetric determination of xanthinol nicotinate at a carbon nanotubes-ionic liquid gel modified electrode

The electrochemistry of xanthinol nicotinate(Xan) was studied by cyclic voltammetry at a glassy carbon electrode modified by a gel containing multi-walled carbon nanotubes(MWNTs) and room-temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate(BMTMPF_6).The modified electrode exhibited good promotion to the electrochemical oxidation of Xan and an ultrasensitive electrochemical method was proposed for the determination of Xan.This method was successfully applied to the determination of...     

An investigation of the dynamical evolution of a class of Bianchi VI−1/9 cosmological models

We consider the evolution of a subclass of the orthogonal spatially homogeneous cosmologies of Bianchi type VI_–1/9. Expansion normalized variables are introduced to write the Einstein field equations for these models as a three-dimensional autonomous system of ordinary differential equations. This system is analyzed qualitatively using the techniques of dynamical systems, and a cosmological interpretation of the phase portraits is given.