Identification of Illegal Drugs with 1064nm Handheld Raman
Written by Edward Geraghty   

When criminal investigations are at stake, there is no margin for error and the demand for fast and accurate mobile techniques for the detection and identification of narcotics is higher than ever before. “Designer” drugs, which are typically contaminated with degraded products, impurities, and unreacted precursors, are entering the market at an alarming rate and are often difficult to detect using traditional methods.

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Often referred to as “party drugs”, methamphetamines, cocaine, MDMA (molly, ecstasy), and heroin have an increasingly negative impact on public health and safety worldwide. It falls to law enforcement officers to remove these dangerous substances from circulation.

Raman spectroscopy is a confirmatory test under Category A by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) and is widely used to support the detection and identification of illegal substances. Previous generations of handheld 785nm Raman-based systems are susceptible to fluorescence interference when analyzing street drugs typically contaminated with degraded products, impurities, and dilutents. The introduction of handheld Raman devices utilizing a 1064nm excitation laser overcomes this limitation and enables law enforcement professionals to identify illegal drugs more easily and quickly. This article will outline how the new generation of handheld Raman detection systems increases the range of materials that can be identified using just one device, providing higher levels of confidence in identification.

The Drug Detection Challenge

Law enforcement professionals are under increasing pressure to identify illegal substances quickly and accurately, but current processes can result in unnecessary delays and questionable results. With a lack of available field-based technologies, forensic drug analysis laboratories typically have the heaviest workload compared to any other crime department. For example, the forensic services section of a local county police department has estimated that the drug evidence submitted to the laboratory accounted for around 60% of the total evidence submissions. Laboratory analytical methods are time consuming and costly. In this case, only 20% of evidence results in court submissions, and so the use of mobile detection technologies for sample screening could save a considerable amount of time, effort and money.

Clandestine drug laboratories are increasingly adding cutting agents such as paracetamol, ketamine, and glucose in an attempt to hamper attempts to successfully detect illegal drugs and narcotics, and many current technologies are unable to identify these materials. In some cases, this means that officers cannot be certain whether the evidence is even worth collecting: it could be a bag of heroin or it could be a cutting agent. They then need to wait for confirmation from a laboratory before pursuing a case in court, wasting valuable time. Handheld Raman utilizing a 1064nm excitation laser offers a solution for the detection of narcotics laced with cutting agents.

Existing Technologies

There are a wide range of technologies currently available for the detection and identification of narcotics and illegal substances. However, when faced with increasingly complex mixtures and active ingredients, some of these techniques are not able to provide the required selectivity or sensitivity.

Spot-testing kits are commonly used in the field to individually test small amounts of a sample using different chemicals to identify the substance. However, the results from these kits can be hard to read and are subject to interpretation unless the user has been properly trained. When criminal investigations are at stake there is no margin for error. Surface wipes can also be used to identify illegal substances but users can only test for one specific drug at a time.

The Raman Effect

Raman spectroscopy can be used to effectively and efficiently identify and distinguish between different materials in liquid and solid forms. Recent advances in instrumentation have led to the successful miniaturization of Raman spectroscopy and the development of portable and handheld Raman for fast sample analysis at the point of need. Portable and handheld Raman devices are used for a broad range of applications including safety and security, pharmaceutical and biopharmaceutical analysis, and food.

In Raman spectroscopy, a laser is focused at the sample and the light scattered is measured to detect changes in its chemical structure and physical characteristics. The Raman spectrum for each compound is unique, and serves as a “chemical fingerprint” that can be used to identify an unknown compound, or a mixture of compounds. Onboard algorithms are used to match the sample’s spectral constituents to an extensive Raman spectral database to provide a positive identification of the sample. Raman is a highly selective technique and has the ability to differentiate between a wide range of compounds, which is critical when faced with an increasingly broad range of threats.

Devices utilizing Raman spectroscopy are ideal tools for analyzing samples because, unlike other handheld detection techniques, analysis can often be performed through packaging material without disturbing the sample. This minimizes exposure to the operator and reduces the risk of sample contamination. Most handheld Raman-based chemical detection systems in use today utilize a 532nm or 785nm laser to excite the sample, which are known to generate heavy sample fluorescence interference making analysis of colored materials extremely challenging. For this reason, the use of handheld Raman-based detection systems has historically been used primarily for identifying white powders and clear liquids, which are the least likely samples to produce fluorescence when excited with a lower excitation laser. However, many real-world samples commonly encountered by law enforcement professionals are colored by impurities from crude synthetic processes or from intentionally added pigments and dyes such as those found in household products including fuel oil and antifreeze. The recent introduction of handheld Raman devices with a 1064nm laser can help to overcome these analysis challenges.

The Power of 1064nm

The high specificity and reduced fluorescence of 1064nm Raman enables users to identify common narcotics as well as identify cutting agents, precursors, clandestine laboratory hazards, and in many cases even the manufacturing source. The high-quality spectra that can be achieved using 1064nm Raman is demonstrated in Figure 1. Figure 2 shows a comparison of an analysis of street heroin using both 785nm and 1064nm Raman and the fluorescence interference occurring during the 785 analysis is clearly shown by the broad curvature of the baseline. By allowing users to perform confirmatory analysis upon arrest and provide substantial, proven evidence, cases can proceed to court much quicker helping to reduce the backlog and increase the success rate of removing dangerous substances from circulation.


Figure 1 (left) — 1064nm Raman spectra of ephedrine HCI (blue) and methamphetamine HCI (red). Figure 2 (right) — Raman spectra of street heroin collected at 1064nm (red) and 785nm (blue).

Protecting evidence from contamination is critical to successfully take a case to court. Handheld Raman can perform analysis through packaging materials such as polymer bags, glass bottles, flasks, and vials, allowing the user to screen materials by non-contact, non-destructive analysis, without needing to open containers and risk contamination. A feature that has received positive feedback from end users is an integrated digital camera that enables users to easily store sample evidence for use in the courtroom.

One handheld Raman device recently underwent a technical evaluation by a third party to evaluate its performance for the identification of illegal drugs using two proprietary detection algorithms. Samples included pure samples of cocaine, heroin, MDMS, and meth, as well as street samples including a case sample that had been identified as cocaine in the field but was later found to be a benign substance when analyzed in the laboratory. The results demonstrated the accuracy of the 1064nm Raman analyzer with 100% matches for all samples. In addition, the sample that had been falsely considered to be a drug and brought to the lab for analysis was quickly identified as magnesium sulfate by the Raman analyzer. Had the device been used to scan incoming material, time, effort, and money could have been saved by avoiding expensive analysis.

The illegal trafficking of drugs and narcotics across borders is an increasing challenge for border control officers who need to be able to quickly and accurately identify a suspicious substance. Raman devices using 785nm excitation lasers cannot perform the analysis that is required and, in one case, a 1064nm laser removed any doubt as to the identity of a suspicious bottle of liquid. Officers at a border checkpoint found a bottle of brown liquid that the owners claimed to be window cleaner. If they had been using a 785nm analyzer, fluorescence interference would have made analysis impossible. However, using a 1064nm Raman analyzer meant that the substance could be analyzed through the bottle and within 15 seconds, the substance was confirmed as liquid methamphetamine.

The introduction of handheld Raman devices utilizing 1064nm technology has increased the range of materials that can be identified using just one device, reducing the number of complementary techniques required for successful narcotics identification. In order to successfully remove these dangerous substances from circulation, law enforcement and border control professionals need to be one step ahead of those responsible for the manufacturing of increasingly complex formulations. In order to support these efforts, technology needs to continually advance to provide confident, cost-effective and comprehensive analysis and the capabilities of handheld Raman make it an attractive solution to meet these needs.


About the Author

Edward Geraghty is Rigaku Analytical Devices’ application scientist. Based out of the company’s Wilmington, Mass. office, Geraghty has worked extensively in the safety and security market sector for more than 30 years in roles that include senior global support chemist for GE Ion Track, and senior chemist for the Massachusetts State Police Crime Laboratory. He has broad experience in the application of handheld, portable CBRNE instrumentation to include Raman, FTIR, IMS, MicroCantilevers and GC/MS technologies. In addition, he has more than 30 years of experience in research and development and has authored three U.S. Patents for new product inventions and their procedural applications.

 

 
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