Justin J. Perry

Determination of quaternary ammonium compounds in seawater samples by solid-phase extraction and liquid chromatography–mass spectrometry

A method for the simultaneous determination of two biocidal quaternary ammonium compounds; didecyldimethylammonium chloride (didecyldimethyl quat) and dodecylbenzyldimethylammonium chloride (benzyl quat), in seawater by solid phase extraction (SPE) followed by liquid chromatography-mass spectrometry (LC-MS) was developed. The optimised procedure utilised off-line extraction of the analytes from seawater using polymeric (Strata-X) SPE cartridges. Recoveries ranged from 80 to 105%, with detection limits at the low parts-per-trillion (ng/l) level for both analytes. To demonstrate sensitivity, environmental concentrations were measured at three different locations along the North East coast of England with measured values in the range 120-270ng/l.

The identification of synthetic organic pigments in modern paints and modern paintings using pyrolysis-gas chromatography–mass spectrometry

AbstractA collection of more than 70 synthetic organic pigments were analysed using pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS). We report on the analysis of diketo-pyrrolo-pyrrole, isoindolinone and perylene pigments which are classes not previously reported as being analysed by this technique. We also report on a number of azo pigments (2-naphthol, naphthol AS, arylide, diarylide, benzimidazolone and disazo condensation pigments) and phthalocyanine pigments, the Py-GC–MS analysis of which has not been previously reported. The members of each class were found to fragment in a consistent way and the pyrolysis products are reported. The technique was successfully applied to the analysis of paints used by the artist Francis Bacon (1909–1992), to simultaneously identify synthetic organic pigments and synthetic binding media in two samples of paint taken from Bacon’s studio and micro-samples taken from three of his paintings and one painting attributed to him. FigureDulux orange paint in the studio of Francis Bacon, now located at Dublin City Gallery, The Hugh Lane

Probing the enantioselectivity of a diverse group of purified cobalt-centred nitrile hydratases

In this study a diverse range of purified cobalt containing nitrile hydratases (NHases, EC 4.2.1.84) from Rhodopseudomonas palustris HaA2 (HaA2), Rhodopseudomonas palustris CGA009 (009), Sinorhizobium meliloti 1021 (1021), and Nitriliruptor alkaliphilus (iso2), were screened for the first time for their enantioselectivity towards a broad range of chiral nitriles. Enantiomeric ratios of >100 were found for the NHases from HaA2 and CGA009 on 2-phenylpropionitrile. In contrast, the Fe-containing NHase from the well-characterized Rhodococcus erythropolis AJ270 (AJ270) was practically aselective with a range of different α-phenylacetonitriles. In general, at least one bulky group in close proximity to the α-position of the chiral nitriles seemed to be necessary for enantioselectivity with all NHases tested. Nitrile groups attached to a quaternary carbon atom were only reluctantly accepted and showed no selectivity. Enantiomeric ratios of 80 and >100 for AJ270 and iso2, respectively, were found for the pharmaceutical intermediate naproxennitrile, and 3-(1-cyanoethyl)benzoic acid was hydrated to the corresponding amide by iso2 with an enantiomeric ratio of >100.

Predicting functional residues of protein sequence alignments as a feature selection task

Determining which residues within a multiple alignment of protein sequences are most responsible for protein function is a difficult and important task in bioinformatics. Here, we show that this task is an application of the standard Feature Selection (FS) problem. We show the comparison of standard FS techniques with more specialised algorithms on a range of data sets backed by experimental evidence, and find that some standard algorithms perform as well as specialised ones. We also discuss how considering the discriminating power of combinations of residue positions, rather than the power of each position individually, has the potential to improve the performance of such algorithms.

Investigation of the materials found in the studio of Francis Bacon (1909–1992)

Abstract The investigation of materials found in Bacons studio is reported. The contents of the studio are examined and interpreted to identify the materials and colours most favoured by Bacon, and the range of media used. A small number of colours appear to have been heavily used. Some objects used as tools in the painting process are also investigated and explain textures seen in paint in his works. Samples of selected materials from the studio are analysed to identify the components of paints (pigments, extenders, and binders) used by Bacon. This investigation is part of a wider project examining his materials and techniques. The analytical information obtained here from the studio helps to clarify the statements made by Bacon in interviews regarding his use of materials and is proving useful in the identification of materials in his paintings, in order to help with the conservation and authentication of his works.

The materials and techniques used in the paintings of Francis Bacon (1909-1992)

Abstract Materials from 38 paintings by Francis Bacon (1909–1992), including 21 complete works and 17 partially destroyed canvases are investigated. Observations are made of the artists technique and details are compiled of the supports used. Samples of paint and priming were taken for analysis using polarized light microscopy, Fourier transform infrared spectroscopy (FTIR), gas chromatography–mass spectrometry (GC–MS), pyrolysis–GC–MS (Py–GC–MS), and scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM–EDX). Analysis of priming layers appears to show that the priming composition correlates well with particular ranges of dates. A fairly limited range of materials are found, with many of the same pigments found in works spanning Bacons career, though other pigments were introduced at different stages in his career. Oil paints were used consistently for the painting of figures, but household paints were increasingly used in backgrounds from the 1960s onwards. A variety of different synthetic media are found in later works, including household acrylic paints and spray paints. Increased knowledge of Bacon’s materials is expected to be of great value to conservators caring for the work of this highly significant artist, and is already helping in the authentication of works attributed to him.

Investigation of the acid/base behaviour of the opium alkaloid thebaine in LC-ESI-MS mobile phase by NMR spectroscopy

As part of a research programme to establish an analytical method for the simultaneous detection of the five major opium alkaloids in poppy seeds by liquid chromatography–electrospray ionization–mass spectrometry (LC-ESI-MS) it was discovered that the inclusion of thebaine produced two peaks for the same compound. This was in contrast to the effective simultaneous detection, by LC-ESI-MS, of morphine, codeine, papaverine and noscapine. The presence of these two peaks for thebaine was investigated using nuclear magnetic resonance spectroscopy with deuterated solvents to emulate the mobile phase conditions experienced. It was found that the presence of 80%, or higher ratios of, water caused two epimeric forms of thebaine to be formed; this explained the presence of two peaks on the chromatogram. In contrast, when a lower water content was used with 1% acetic acid, one stable form of thebaine could be analysed and resulted in a single peak visible in the subsequent chromatography.

Supplementary material from "Investigation of the acid/base behaviour of the opium alkaloid thebaine in LC-ESI-MS mobile phase by NMR spectroscopy"

As part of a research programme to establish an analytical method for the simultaneous detection of the five major opium alkaloids in poppy seeds by liquid chromatography–electrospray ionization–mass spectrometry (LC-ESI-MS) it was discovered that the inclusion of thebaine produced two peaks for the same compound. This was in contrast to the effective simultaneous detection, by LC-ESI-MS, of morphine, codeine, papaverine and noscapine. The presence of these two peaks for thebaine was investigated using nuclear magnetic resonance spectroscopy with deuterated solvents to emulate the mobile phase conditions experienced. It was found that the presence of 80%, or higher ratios of, water caused two epimeric forms of thebaine to be formed; this explained the presence of two peaks on the chromatogram. In contrast, when a lower water content was used with 1% acetic acid, one stable form of thebaine could be analysed and resulted in a single peak visible in the subsequent chromatography.