Tracking the history of polycyclic aromatic compounds in London through a River Thames sediment core and ultrahigh resolution mass spectrometry.

Polycyclic aromatic compounds (PACs), including polycyclic aromatic hydrocarbons (PAHs) and heteroatom-containing analogues, constitute an important environmental contaminant class. For decades, limited numbers of priority PAHs have been routinely targeted in pollution investigations, however, there is growing awareness for the potential occurrence of thousands of PACs in the environment. In this study, untargeted Fourier transform ion cyclotron resonance mass spectrometry was used for the molecular characterisation of PACs in a sediment core from Chiswick Ait, in the River Thames, London, UK. Using complex mixture analysis approaches, including aromaticity index calculations, the number of molecular PAC components was determined for eight core depths, extending back to the 1930s. A maximum of 1676 molecular compositions representing PACs was detected at the depth corresponding to the 1950s, and a decline in PAC numbers was observed up the core. A case linking the PACs to London's coal consumption history is presented, alongside other possible sources, with some data features indicating pyrogenic origins. The overall core profile trend in PAC components, including compounds with oxygen, sulfur, nitrogen, and chlorine atoms, is shown to broadly correspond to the 16 priority PAH concentration profile trend previously determined for this core. These findings have implications for other industry-impacted environments.

Investigating the Influence of n-Heptane versus n-Nonane upon the Extraction of Asphaltenes.

The composition of asphaltenes is of interest due to the challenges they pose for industry and their high complexity, encompassing a range of heteroatom contents, molecular weights, double bond equivalents (DBEs), and structural motifs. They are well-known for aggregating above critical concentrations, hindering the upstream and downstream processes. Asphaltenes are defined by solubility, as they are insoluble in light paraffins such as n-heptane and soluble in aromatic solvents such as toluene. Today, enormous efforts are being invested into the characterization of asphaltenes to shed light into their structural profiles to benefit the petroleum industry and environmental sustainability. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) provides molecular level analysis with unparalleled mass resolving power and mass accuracy, which is vital for the characterization of inherently complex crude oils and their asphaltene fractions. The aim of this research is to elucidate and compare the compositional profiles of asphaltene fractions of two petroleum samples, fractioned through two approaches: using n-heptane, as is typical practice, and n-nonane, for the purpose of testing extraction using higher molecular weight alkanes. The results highlight that the choice of solvents does indeed influence the accessibility of different species and therefore changes the observed molecular profiles of the extracted asphaltenes. n-Heptane afforded broader contributions of different heteroatomic classes and greater carbon number ranges of the observed components; the DBE distribution vs carbon number profiles were different, where the extracts produced using n-nonane displayed a greater prevalence of lower DBE species.

Sequential processing strategies for fingermark visualisation on uncirculated £10 (Bank of England) polymer banknotes.

An investigation was undertaken to assess the relative effectiveness of five fingermark visualisation process sequences on new, uncirculated £10 polymer banknotes from the Bank of England (BoE). Each sequence was challenged with the visualisation of 64 natural fingermarks on eight banknotes, of which half were aged for 2-3days and half were aged for 12-13days (32 donors contributed in each set). The sequences investigated were; After each process was applied, fingermark development was assessed under primary viewing conditions appropriate to the technique (white light or fluorescence). All samples were also assessed under secondary viewing conditions; provided by the optical processes infrared reflection and long-wave ultraviolet reflection, and by gelatin lifting (with scanning). These additional techniques reduced the interfering effect of the complex banknote backgrounds and improved the contrast of enhanced fingermarks. Overall, with all assessment conditions considered, sequence 4 and sequence 3 visualised the most identifiable quality fingermarks (92.2% and 89.1% respectively). The most effective overall process used singularly was found to be black magnetic powder, provided that reflected infrared was used to image the results (82.8%). Further data analysis revealed that sequence 1 was the most effective sequence for fresh marks (aged 2-3days) when only primary viewing conditions within the visible part of the spectrum are considered. The need for further work which considers the sensitivity of the processes, and how they perform on BoE polymer banknotes that have become worn in circulation, is emphasised.

Fingermark visualisation with iron oxide powder suspension: The variable effectiveness of iron (II/III) oxide powders, and Tween® 20 as an alternative to Triton™ X-100.

The effectiveness of the current UK iron oxide powder suspension formulation, 'C-IOPS-09' (Triton X-100 based), for fingermark or latent fingerprint visualization is shown to be affected by variations between batches of the recommended iron oxide powder from Fisher Scientific (I/1100/53). When incorporated into the C-IOPS-09 formulation, a 2015 powder batch resulted in the detection of ∼19% fewer fingermarks, of broadly reduced contrast, when compared to powder suspension prepared with a 2008 batch of the same product. Furthermore, the 2015 powder batch was found to be unsuitable in experimental reduced-surfactant concentration powder suspension, because it caused surface-wide or background staining. The studies in this paper also investigated the use of Tween 20 surfactant as an alternative to the currently utilised Triton X-100, in preparation for the potential unavailability of Triton X-100 in the future. Powder suspensions prepared with Tween 20 surfactant solutions of 4% and 40% were shown to offer similar effectiveness to the currently recommended C-IOPS-09 formulation, when compared using the same batch of Fisher Scientific iron oxide powder (2008 or 2015). The difference between the 2008 and 2015 iron oxide batches was hence also evident with these alternative surfactant solutions. Particle size distribution analysis of the iron oxide powders in Tween 20 and Triton X-100 based surfactant solutions show that the more effective powder exhibits a higher sub-micrometre particle population than the less effective powder. This work leads to an improved specification for powder suspension formulations. This is demonstrated with an example powder suspension formulation which uses a 10% Tween 20 surfactant solution and iron oxide nanopowder (50-100nm) from Sigma Aldrich, which was shown to visualise 27% more fingermarks than the C-IOPS-09 formulation prepared with the 2015 Fisher Scientific powder batch, in a comparative study.

Fingermark visualisation on uncirculated £5 (Bank of England) polymer notes: Initial process comparison studies.

Experiments were conducted to investigate the effectiveness of a range of fingermark visualisation processes on brand new, uncirculated, £5 polymer banknotes (and their test note predecessors), as produced by the Bank of England (BoE). In the main study of this paper, a total of 14 individual processes were investigated on BoE £5 polymer banknotes, which included both 'Category A' processes (as recommended in the Home Office Fingermark Visualisation Manual) as well as recently developed processes, including fpNatural® 2 powder (cuprorivaite) from Foster+Freeman and a vacuum metal deposition sequence that evaporates silver followed by zinc. Results from this preliminary investigation indicate that fpNatural® 2, multimetal deposition, Wet Powder™ Black, iron oxide powder suspension and black magnetic powder are the most effective processes on these uncirculated £5 BoE polymer banknotes, when viewed under "primary viewing" conditions (white light or fluorescence). Additional fingermarks were visualised on the polymer banknotes following the subsequent use of reflected infrared imaging and lifting techniques, and with the benefit of these techniques taken into consideration, the aforementioned processes remained amongst the most effective overall. This work provides initial insight into fingermark visualisation strategies for BoE £5 polymer banknotes, and the need for further studies in order to generate mature operational guidance is emphasised.