Relatively little work has been reported on the post-discharge GSR content of Accepted 21 March non-metallic inorganic or low molecular weight organic anions to distinguish between different Available online 12 April ammunition types. The development of an analytical method using suppressed micro-bore anion exchange chromatography IC is presented for the analysis of GSR. Along with an optimised chromatography Gunshot residue extraction procedure, this method was applied to the analysis of post-ignition residues from three Firearms selected ammunition types.
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All rights reserved. More recently, the emergence of primers free Gunshot residue GSR is the material emitted by ammunition from heavy metals , has meant that the possibility for false during discharge. This includes particles from the primer, negatives has also increased. These compounds include nitroglycerine and isomers of microscopy coupled with energy dispersive X-ray spectroscopy dinitrotoluene which originate mostly from the propellant. With tography HPLC  and capillary electrophoresis CE  have the potential to identify and characterise even 1 mm diameter all been applied to the analysis of organic components of GSR and particles, this is a very useful tool used in practical forensic GC coupled with thermal energy analysis TEA or mass casework .
However that said, analysis times are often lengthy spectrometry MS are the most prominent. However, this several days , and SEM-EDX is generally only used to examine the technique requires compounds to be volatile and thermally stable metallic particles found in GSR, commonly lead, antimony and and therefore can be unsuitable for some compounds, such as barium. It is not possible to speciate anionic counter ions with this nitrocellulose .
Furthermore, loss of organic compounds over technique. False positives have also been observed with signature several hours has been shown, making this type of analysis time- dependent. Gilchrist et al. Johns et al. CE is it was possible to distinguish between explosive types . With complementary to IC in many ways, and it is advantageous to use primer mixes typically made from metal sulphides, nitrates, both techniques in a forensic context . The ability to speciate gives IC types.
Kolla also investigat- examining their relative ion mass ratios and any potential sources ed the use of IC for explosives, using a potassium hydrogen of interference. To the best of our knowledge, this represents the phthalate eluent, focussing on chloride, nitrate and sulphate . As many similar ions were present in the environment, internal ratios between a typically non- 2.
Reagents explosives related anion and an energetic anion were calculated to All reagents were of analytical or reagent grade. Previous work by Acros Organics, Geel, Belgium , chlorate, perchlorate, bromate, cyanate and Wheals and Ellison demonstrated that it was possible to use anion thiosulphate Sigma—Aldrich, Gillingham, Dorset, UK were prepared from their sodium salts; sulphate was prepared from its copper salt BDH.
Phosphate exchange chromatography to determine the quantity of nitrite and standards were prepared from its potassium salts BDH ; carbonate and threonate nitrate anions generated through degradation of nitrocelluloses were prepared from their calcium salts Sigma ; acetate BDH , and thiocyanate and nitroglycerine commonly present in propellants. This study were prepared from their ammonium salts, with formate being prepared from an also showed that their relative concentration ratios could be ammonium solution Sigma.
With regard to GSR in and benzoate Sigma were prepared from their acids. Where necessary, all and nitrate . As primers and propellants differ among eluents, stocks, standards and samples were prepared using ultrapure water manufacturers, anion content is likely to differ, and could provide Chlorate, perchlorate, nitrite, cyanate, phosphate and To show the technology in practice, we recently reported the organic acids stock standards were kept in the dark at 4 8C and were re-prepared use of capillary-bore IC to detect energetic material residues in fortnightly.
However, in order to were performed using Chromeleon 6.
In order to achieve acceptable anion derive any forensic conclusions, more work is required to sensitivity, the injection volume was 40 mL. In order to separate all species, a hydroxide associated limits of variation. Recent work by Hutchinson et al. Whilst the sensitivity of the C4D was been shown to be more sensitive than the more traditional indirect photometric detection, limits of detection LODs are still 2.
GSR collection and sample preparation approximately an order of magnitude higher than when using Twenty-nine cartridges of each of a 0. CE has also and were analysed within 2 weeks. Any residue on the outside of the nitrate during method development. Perchlorate salts seem to be cartridge was therefore not considered. Residues from a spent brake pad lining from the rear axle of a DAF 85 Tractor Unit were obtained by in this work. Results and discussion improved selectivity. Furthermore, it was thought that the In a recent review by Dalby et al.
A short experiment to investigate the their contribution to GSR . Optimisation of extraction methods for residues deposited on a surface 3. Suppressed anion exchange chromatography method development Three extraction solvent types for GSR were investigated: ultra pure water; 40 mM hydroxide; and methanol:water. For anion exchange chromatography, two micro-bore columns An initial investigation into the use of cotton swabs to collect were chosen for analytical method development.
By comparison, GSR revealed high levels of organic acids and nitrate in blank the IonPac AS11 is a moderately lower capacity ion exchange resin extracts in ultra pure water see SI, Fig. When pre-rinsed at Alternatively, the AS20 offers sonicated for 10 incremental time periods from 0 to 60 min in enhanced selectivity for oxyhalides and perchlorate in particular duplicate to establish the optimum extraction time see SI, Fig.
For GSR, ultra pure water offered the best results in comparison to the AS20 phase as expected data not shown. Surprisingly, and Attempts to separate all species under gradient elution conditions despite target analyte polarities, it was found that 30 min was revealed that the AS20 phase was the most suitable with a gradient required to extract most species to an acceptable level in a of 5—40 mM hydroxide over 23 min.
Furthermore, hydroxide extraction solutions resulted analysis . Regarding brake lining residue analysis, it was found thiocyanate as more forensically important target species for GSR.
Author's personal copy E. Method performance respectively in comparison to that of the 0. Previous research using solid phase micro-extraction and GC Table 1. The 0. Isocyanates are the closest relative species R—N5 5C55O training in comparison to more modern systems which employ additional electrolytic devices to achieve greater sensitivity.
Whilst residues contained similar species CO SCN- in all three cases, it was possible to distinguish between 19 1 ClO4- ammunition types by quantitative assessment of the ions present Standard Fig. By expressing all levels detected as an 0. Chloride, carbonate and sulphate were observed in all 0. Furthermore, a peak corresponding Time min to the retention time of bromate was observed in some casing Fig. Sample chromatograms of i a 0. Chromatograms offset on signal axis by 5 mS for clarity. Author's personal copy 54 E.
In particular, threonate was shown to retain poorly on high capacity ion exchange resins though was not found to match that of the unknown species observed here. Interpretation of direct infusion mass spectra suggested the presence of a related species, glyceric acid 2,3-dihydroxypropano- ate. It is both interesting and important to note that this species could have also arisen from nitroglycerine which shares some structural similarity with ascorbic acid. The mass spectrum of this species is shown in SI, Fig.
No azide, chlorate or perchlorate were detected in any of the three ammunition types studied here, though it was unclear whether salts of these ions were used during production. Quantitation of species deposited on the inner casing wall after discharge could act as a basis to study the degree of transfer to any external surface in future studies. Depending on the level of use and area covered, these species on the hands are therefore likely to be present at much higher levels. The only reported research in this area to date has focussed on the determination of nitrite-to-nitrate signal Fig.
Box plot of the main anions of interest in a 0. As residue, a 0. Furthermore, intact aromatic isocyanates have between ammunition types Fig. Of particular interest was been determined previously by cation exchange rather than anion the cyanate—thiocyanate ratio Fig. This showed that there exchange chromatography . This ratio however may suffer less interfer- expected . Supplementary statistical tests by the same company, a similarity in their composition was were also performed on the data to explore whether there is any expected though quantitative assessment highlighted some relationship between the ammunition types and the weights of differences.
On average, thiocyanate was observed at its highest the anions see SI, Table S3. Interferences in alternative matrices relevant to GSR analysis by observed in all extracts of all three cartridge residues Peak 1, IC Fig. Whilst anions were peak collected in a vial from the detector outlet. This commercial vehicle as a black powder substitute. Scatter plots showing the correlation between the weights of a nitrite and nitrate, b formate and cyanate, c cyanate and thiocyanate for each ammunition residue. This which could disrupt their approximate ratio 0.
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One seminal book is Boxwell's Benchmarking for Competitive Advantage Robert Camp who wrote one of the earliest books on benchmarking in  developed a stage approach to benchmarking. The cost of benchmarking can substantially be reduced through utilizing the many internet resources that have sprung up over the last few years. These aim to capture benchmarks and best practices from organizations, business sectors and countries to make the benchmarking process much quicker and cheaper.
The technique initially used to compare existing corporate strategies with a view to achieving the best possible performance in new situations see above , has recently been extended to the comparison of technical products. This process is usually referred to as "technical benchmarking" or "product benchmarking". Its use is well-developed within the automotive industry "automotive benchmarking" , where it is vital to design products that match precise user expectations, at minimal cost, by applying the best technologies available worldwide.
Data is obtained by fully disassembling existing cars and their systems. Such analyses were initially carried out in-house by car makers and their suppliers.
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