Rhiannon Alder

The analysis of drug material in the field is an important function of law enforcement agencies, forensic drug laboratories, and drug checking services. Portable testing techniques employed by these different groups range from inexpensive screening tools with low discriminating power, such as presumptive chemical color tests, to more sophisticated portable analytical techniques that behave as miniaturized versions of their laboratory counterparts, such as gas chromatography–mass spectrometry (GC–MS). Rapid non‐destructive analysis in the field and non‐laboratory environments is afforded by portable and handheld Fourier transform infrared (FTIR) spectrometers with little to no sample preparation, while handheld Raman analyzers have the added potential for drug material identification through sealed packaging using spatially offset Raman spectroscopy (SORS). Utilization of the most suitable testing technique for the given environment is demonstrated at international borders and airports wherein ion mobility spectroscopy (IMS) is frequently employed for the detection of drug (and explosive) residues owing to its ease of operation and rapid analysis. Advances in technology and materials have provided analysts with new portable testing techniques, including paper spray ionization–MS (PSI‐MS), an ambient MS technique that provides sensitive, rapid, and reliable analysis without the need for sample preparation steps. A growing area of research and interest in the development of sensitive and selective optical and electrochemical portable (bio)sensors for in‐field analysis of drug material indicates that new commercial sensors for drug detection will be available in the foreseeable future.This article is categorized under: Forensic Chemistry and Trace Evidence > Controlled and Emerging Drug Compounds Forensic Chemistry and Trace Evidence > Emerging Technologies and Methods Toxicology > Drug Analysis

Surface-enhanced Raman spectroscopy (SERS) technology is an attractive method for the prompt and accurate on-site screening of illicit drugs. As portable Raman systems are available for on-site screening, the readiness of SERS technology for sensing applications is predominantly dependent on the accuracy, stability and cost-effectiveness of the SERS strip. An atmospheric-pressure plasma-assisted chemical deposition process that can deposit an even distribution of nanogold particles in a one-step process has been developed. The process was used to print a nanogold film on a paper-based substrate using a HAuCl₄ solution precursor. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the gold has been fully reduced and that subsequent plasma post-treatment decreases the carbon content of the film. Results for cocaine detection using this substrate were compared with two commercial SERS substrates, one based on nanogold on paper and the currently available best commercial SERS substrate based on an Ag pillar structure. A larger number of bands associated with cocaine was detected using the plasma-printed substrate than the commercial substrates across a range of cocaine concentrations from 1 to 5000 ng/mL. A detection limit as low as 1 ng/mL cocaine with high spatial uniformity was demonstrated with the plasma-printed substrate. It is shown that the plasma-printed substrate can be produced at a much lower cost than the price of the commercial substrate.

The use of illicit drugs across the world causes issues for users, healthcare workers and the public. Therefore, rapid and reliable onsite testing methods to detect these drugs are required. In this study, seven commercial surface‐enhanced Raman spectroscopy (SERS) substrates A–G were compared for the analysis of cocaine. These substrates were compared using scanning electron microscopy to study the surface structure and Raman spectroscopy and to determine if there was any enhancement of the cocaine bands. Substrate B provided the best enhancement of known cocaine vibrational bands, allowing the detection down to concentrations of 1 ng/mL in standards and 10 ng/mL extracted from the oral fluid. The results showed that SERS is an ideal method for future rapid onsite analysis of illicit drugs in oral fluid. Commercial SERS substrates were compared for the analysis of cocaine. Substrate B provided the best result and was further tested with lower concentrations and extracts from the oral fluid. The application to oral fluid testing could prove useful for future onsite analysis.

Cocaine trafficking in the form of textile impregnation is routinely encountered as a concealment method. Raman spectroscopy has been a popular and successful testing method used for in situ screening of cocaine in textiles and other matrices. Quantitative analysis of cocaine in these matrices using Raman spectroscopy has not been reported to date. This study aimed to develop a simple Raman method for quantifying cocaine using atropine as the model analogue in various types of textiles. Textiles were impregnated with solutions of atropine in methanol. The impregnated atropine was extracted using less hazardous acidified water with the addition of potassium thiocyanate (KSCN) as an internal standard for Raman analysis. Despite the presence of background matrix signals arising from the textiles, the cocaine analogue could easily be identified by its characteristic Raman bands. The successful use of KSCN normalised the analyte signal response due to different textile matrix background interferences and thus removed the need for a matrix‐matched calibration. The method was linear over a concentration range of 6.25–37.5 mg/cm² with a coefficient of determination (R²) at 0.975 and acceptable precision and accuracy. A simple and accurate Raman spectroscopy method for the analysis and quantification of a cocaine analogue impregnated in textiles has been developed and validated for the first time. This proof‐of‐concept study has demonstrated that atropine can act as an ideal model compound to study the problem of cocaine impregnation in textile. The method has the potential to be further developed and implemented in real world forensic cases.