Niamh NicDaeid

Rapid quantitative colourimetric tests for trinitrotoluene (TNT) in soil

A rapid quantitative colourimetric test was developed for the determination of 2,4,6-Trinitrotoluene (TNT) in soil. Quantification was achieved using an innovative application of photography where the relationship between the Red Green Blue (RGB) value and concentration of colorimetric product was exploited. The wide linear range (1-50 mg/L) and low detection limit (0.73±0.01 mg/L to 3.5±0.4 mg/L) achieved was comparable with spectrophotometric quantification methods. Quantification was validated both with known concentration standards and spiked soil extracts confirming the accuracy of the technique. The results demonstrate a powerful technique with the capacity for development as a rapid on site field test for the analysis of explosives.

A comparison of multi-metal deposition processes utilising gold nanoparticles and an evaluation of their application to ‘low yield’ surfaces for finger mark development

This paper reports a comparison of the effectiveness and practicality of using different multi-metal deposition processes for finger mark development. The work investigates whether modifications can be made to improve the performance of the existing process published by Schnetz. Secondly, we compare the ability of different multi-metal deposition processes to develop finger marks on a range of surfaces with that of other currently used development processes. All published multi-metal deposition processes utilise an initial stage of colloidal gold deposition followed by enhancement of the marks with using a physical developer. All possible combinations of colloidal gold and physical developer stages were tested. The method proposed by Schnetz was shown to be the most effective process, however a modification which reduced the pH of the enhancement solution was revealed to provide the best combination of effectiveness and practicality. In trials comparing the modified formulation with vacuum metal deposition, superglue and powder suspensions on surfaces which typically give low finger mark yields (cling film, plasticised vinyl, leather and masking tape), the modified method produced significantly better results over existing processes for cling film and plasticised vinyl. The modified formulation was found to be ineffective on both masking tape and leather. It is recommended that further tests be carried out on the modified multi-metal deposition formulation to establish whether it could be introduced for operational work on cling film material in particular.

Chemical enhancement of footwear impressions in blood deposited on fabric — Evaluating the use of alginate casting materials followed by chemical enhancement

Most footwear marks made in blood on a surface such as fabric tend to be enhanced in situ rather than physically recovered using a lifting technique prior to enhancement. This work reports on the use of an alginate material to recover the impressed footwear marks made in blood and deposited on a range of fabric types and colours. The lifted marks were then enhanced using acid black 1 and leuco crystal violet with excellent results. This presents a new method for the lifting and recovery of blood impressions in situ from crime scene followed by subsequent mark enhancement of the lifted impression.

Classification and Source Determination of Medium Petroleum Distillates by Chemometric and Artificial Neural Networks: A Self Organizing Feature Approach

Three different medium petroleum distillate (MPD) products (white spirit, paint brush cleaner, and lamp oil) were purchased from commercial stores in Glasgow, Scotland. Samples of 10, 25, 50, 75, 90, and 95% evaporated product were prepared, resulting in 56 samples in total which were analyzed using gas chromatography-mass spectrometry. Data sets from the chromatographic patterns were examined and preprocessed for unsupervised multivariate analyses using principal component analysis (PCA), hierarchical cluster analysis (HCA), and a self organizing feature map (SOFM) artificial neural network. It was revealed that data sets comprised of higher boiling point hydrocarbon compounds provided a good means for the classification of the samples and successfully linked highly weathered samples back to their unevaporated counterpart in every case. The classification abilities of SOFM were further tested and validated for their predictive abilities where one set of weather data in each case was withdrawn from the sample set and used as a test set of the retrained network. This revealed SOFM to be an outstanding mechanism for sample discrimination and linkage over the more conventional PCA and HCA methods often suggested for such data analysis. SOFM also has the advantage of providing additional information through the evaluation of component planes facilitating the investigation of underlying variables that account for the classification.

The role of isotope ratio mass spectrometry as a tool for the comparison of physical evidence

This paper considers how likelihood ratios can be derived for a combination of physical, chemical and isotopic measurements. Likelihood ratios were formulated based on the characteristics of a small convenience sample of 20 duct tapes. The propositions considered were: The physical and isotopic characteristics of ten rolls of duct tape were shown to be consistent throughout each roll. The width and thickness of the tapes and the density of the scrim fibres provided equivalent information and the combined physical characteristics provided a basis upon which to discriminate between many of the samples. Scatter-plots and confidence ellipses provided a convenient method to group the isotopic composition of the tape backing material and provided a basis to discriminate between samples which were physically indistinguishable. Considering both the physical and isotopic characteristics it was possible, at best, to ascertain that the evidence provided moderately strong support for the proposition that two samples of tape were derived from the same batch (LR=400). Kernel density estimates were used to model the distribution of isotopic compositions of the backing material. Using this technique it was possible to estimate objectively the probability that a sample with given characteristics could be drawn, at random, from the background population and to calculate a likelihood ratio based on the propositions above. The strength of evidence which could be presented by either model was ultimately limited by the size of the background sample.

Controlling the variable of pressure in the production of test footwear impressions

Footwear impression lifting and enhancement techniques may be affected by several variables introduced during the production of test footwear impressions, thus limiting the usefulness of enhancement technique comparisons and the results obtained. One such variable is the force applied when the impressed mark is being made. Producing consistent test impressions for research into footwear enhancement techniques would therefore be beneficial. This study was designed to control pressure in the production of test footwear impressions when mimicking a stamping action. Twenty-seven volunteers were asked to stamp on two different surfaces and the average stamping force was recorded. Information from the data obtained was used to design and build a mechanical device which could be calibrated to consistently deliver footwear impressions with the same force onto a receiving surface. Preliminary experiments using this device and different contaminants on the footwear sole have yielded consistent and repeatable impressions. Controlling the variable of pressure for the production of test impressions in this study demonstrated that the differences observed were visual (due to the amount of contaminant transferred and subsequent enhancement) and did not affect the replication of outer sole characteristics. This paper reports the development of the device and illustrates the quality of the impressions produced.

Clarification of route specific impurities found in methylamphetamine synthesised using the Birch method.

This paper focuses on the determination of route specific impurities produced when methylamphetamine is synthesised using the Birch reduction. Previous work available in the scientific literature reported only one route specific impurity using ephedrine hydrochloride as the starting material. In this paper we investigated the impurity profiles of methylamphetamine produced from both the salt and base forms of ephedrine and pseudoephedrine. A new previously unreported route specific impurity was revealed as was the potential absence of the previously reported impurity in the profile of samples prepared from the free base.

Chemical enhancement of footwear impressions in urine on fabric

A range of chemical techniques were utilised for the enhancement of footwear impressions deposited on a variety of fabric types of different colours with urine as a contaminant. A semi-automated stamping device was used to deliver test impressions at a set force to minimise the variability between impressions; multiple impressions were produced and enhanced by each reagent to determine the repeatability of the enhancement. Urine samples from different donors were analysed using a spectrofluorophotometer revealing differences between individuals. Results indicated that the enhancement of footwear impressions in urine was possible using amino acid staining techniques whereas protein stains failed to achieve successful enhancement.

Elemental profiling using ICPMS of methylamphetamine hydrochloride prepared from proprietary medication using the Moscow and hypophosphorous synthesis

Illicit drugs manufactured from clandestine laboratories are often impure due to poor laboratory conditions, variations in synthesis and impure starting materials extracted either from common household products or pharmaceutical grade chemicals. Inductively coupled plasma mass spectrometry (ICPMS) can be utilised as a multi-element analytical tool to elicit the inorganic impurities which may be present in such samples, however the interpretation of the resultant data can be problematic and complex. This is particularly true when dealing with seized samples of unknown provenance. In this work, we have presented and interpreted inorganic profiles as a means to explore within and between batch variations in known provenance samples produced via two different popular synthetic routes. Samples were prepared from essential chemicals recovered from household materials and pharmaceutical medication available in the UK and extracted using different solvents. The presence or absence of elements in the final synthesised products could be linked to the synthesis route, salting out method and potentially the solvent used in the precursor extraction process.

Chemical enhancement of footwear impressions in blood on fabric — Part 3: Amino acid staining

Enhancement of footwear impressions, using ninhydrin or ninhydrin analogues is not considered common practice and such techniques are generally used to target amino acids present in fingermarks where the reaction gives rise to colour and possibly fluorescence. Ninhydrin and two of its analogues were used for the enhancement of footwear impressions in blood on various types, colours and porosities of fabric. Test footwear impressions on fabric were prepared using a specifically built rig to minimise the variability between each impression. Ninhydrin enhancement of footwear impressions in blood on light coloured fabric yielded good enhancement results, however the contrast was weak or non-existent on dark coloured fabrics. Other ninhydrin analogues which have the advantage of fluorescence failed to enhance the impressions in blood on all fabrics. The sequential treatment of impressions in blood on fabric with other blood enhancing reagents (e.g. protein stains and heme reagents) was also investigated.