Electrochemiluminescence detection of methamphetamine in biological matrices

We have studied an electrochemical detection method for the stimulants in the forensic samples using electrochemiluminescence (ECL). In this context, amphetamine type stimulant (methamphetamine (MA)) has been studied as co-reactants in the [Ru(bpy)3]2+ (where bpy is 2,2’-bipyridine) ECL system. This approach is developed based on a glassy carbon electrode modified with [Ru(bpy)3]2+ /Nafion composite film. LoD, LoQ and linear working range for MA are studied currently. The ECL intensity was found to be concentrations over the range of 5 x 10-8 to 2.5 x 10-4mol/L. LoD for MA is 1.94 x 10-10 mol/L. The regression coefficient is 0.9931 for the experiment. Our approach was applied in different medium such as saliva and human serum to detect MA This technique is simple, rapid, selective and sensitive, and shows potential for the high throughput quantitation of MA. the results show that the present electrochemical approach seems to provide a sensitive detection of MA in forensic applications

Voltammetry as a rapid screening method for NPS identification

Designer drugs, also commonly known as new psychoactive substances (NPS), are increasingly in their prevalence and a challenge to toxicologists and forensic chemists. Synthetic cannabinoids (SCs) are among the largest group of NPS that have emerged in the illicit drug market all over the world. SCs may consist of different chemicals prepared in laboratories and herbal mixtures that said to be incense and not-for-human-consumption. The main aim of this paper is to investigate the use of electrochemical based methods for screening some of the emerging types of SC. More specifically, the paper takes electrochemistry approach called voltammetry to perform the detection and analysis of SCs whereby the main subjects for screening include STS-135 and 5F-ADB-PINACA. The expected result is that those compounds that belong to the same class should indicate almost similar behaviour to help achieve its objective, the paper reviews a number of recent publications relating to forensic drug analysis and much attention to electrochemical sensor methods

ESR, raman and conductivity studies on fractionated poly(2-methoxyaniline-5-sulfonic acid)

Synthesis methods used to produce poly(2-methoxyaniline-5-sulfonic acid) (PMAS), a water soluble, self-doped conducting polymer, have been shown to form two distinctly different polymer fractions with molecular weights of approximately 2 kDa and 8 -10 kDa. The low molecular weight (LMWT) PMAS fraction is redox inactive and non-conducting while the high molecular weight (HMWT) PMAS is electro-active with electrical conductivities of 0.94 0.05 S cm-1. Previous investigations have illustrated the different photochemical and electrochemical properties of these fractions, but have not correlated these properties with the structural and electronic interactions that drive them. Incomplete purification of the PMAS mixture, typically via bag dialysis, has been shown to result in a mixture of approximately 50:50 HMWT:LMWT PMAS with electrical conductivity significantly lower at approximately 0.10 to 0.26 S cm-1. The difference between the electrical conductivities of these fractions has been investigated by the controlled addition of the non-conducting LMWT PMAS fraction into the HMWT PMAS composite film with the subsequent electronic properties investigated by solid-state ESR and Raman spectroscopies. These studies illustrate strong electronic intereactions of the insulating LMWT PMAS with the emeraldine salt HMWT PMAS to substantially alter the population of the electronic charge carriers in the conducting polymer. ESR studies on these mixtures, when compared to HMWT PMAS, exhibited a lower level of electron spin in the presence of LMWT PMAS indicative of the the formation of low spin bipolarons without a change the oxidation state of the conducting HMWT fraction

Improved performance of porphyrin-based dye sensitised solar cells by phosphinic acid surface treatment

Chemical surface treatment of porphyrin-sensitised titania films using bis-(4-methoxyphenyl) phosphinic acid after dye adsorption, results in large improvements in DSSC efficiencies which originate primarily from higher short circuit currents. The result was attributed to a positive shift in the TiO2 quasi-Fermi level with simultaneous retardation of charge recombination. High device performances have been achieved even using simplified electrolyte matrices devoid of the common additives, LiI and t-butylpyridine

Novel detection approaches to tackle the challenges of complex matrices for alternative drugs and new psychoactive substances

This chapter focuses on the challenges faced by forensic practitioners in regard to the detection of novel psychoactive substances. With the ever-evolving nature of these substances it has become clear that the long-established methods employed for the detection of traditional illicit drugs are not translatable to this new drug trend. As such the forensic community is required to adapt these protocols and consider alternative techniques. This chapter aims to highlight some of these alternative techniques and discuss the advantages they can offer alongside their current limitations, with a particular focus upon detection in complex matrices

Electronic interactions within composites of polyanilines formed under acidic and alkaline conditions. Conductivity, ESR, Raman, UV-vis and fluorescence studies

The properties of two forms of polyaniline (PAni) synthesised under acidic and basic conditions have been investigated both individually and as combined complexes. The PAni polymerised within alkaline media was redox inactive and non-conducting while the PAni emeraldine salt (ES) was electroactive and conducting. Raman, electron spin resonance, UV-Vis and fluorescence spectroscopies were used to monitor the changes in electronic properties of these conducting polymer composites. Solution cast films of alkaline synthesised (A-PAni) with the PAni ES resulted in an increase in the high spin polaron population suggesting that it acts as a pseudodopant. The ability of the A-PAni to increase and maintain the population of the polaron charge carrier was confirmed by UV-vis and Raman spectroscopy. Significantly, the presence of the A-PAni in PAni ES helped to sustain higher electrical conductivities at loading levels that were well below the percolation threshold of an insulating polystyrene sulfonate polymeric oligomer model. Fluorescence studies indicated that the A-PAni was fluorescent. However, mixtures of A-PAni with the PAni ES resulted in quenching of the A-PAni emission. The quenching process was observed to involve both static and dynamic processes, with the static quenching being dominant. These results suggest that the two polymers are strongly associated with each other when in the solid state. In stark contrast, the alkaline synthesized PAni did not influence the electrochemical properties of the emeraldine salt. These results deviate significantly from the expected outcome of the addition of an insulating A-PAni additive and highlight the unusual interactions occurring between PAni and its alkaline analogue. © the Owner Societies 2011

Analysis of DNA from Fired Cartridge Casings

DNA analysis has been widely accepted as providing valuable evidence concerning the identity of the source of biological traces. Our work has showed that DNA samples can survive on cartridges even after firing. The study also raised the possibility of determining other information such as the age of the donor. Such information may be invaluable in certain cases where spent cartridges from automatic weapons are left behind at the scene of a crime. In spite of the nature of touch evidence and exposure to high chamber temperatures during shooting, we were still capable to retrieve enough DNA for profile typing. In order to estimate age of contributor, DNA methylation levels were analyzed using EpiTect system for retrieved DNA. However, results were not conclusive, due to low amount of input DNA