Infrared and Raman screening of seized novel psychoactive substances: a large scale study of >200 samples

Abstract

The potential of IR absorption and Raman spectroscopy for rapid identification of novel psychoactive substances (NPS) has been tested using a set of 221 unsorted seized samples suspected of containing NPS. Both IR and Raman spectra showed large variation between the different sub-classifications of NPS and smaller, but still distinguishable, differences between closely related compounds within the same class. In initial tests, screening the samples using spectral searching against a limited reference library allowed only 41% of the samples to be fully identified. The limiting factor in the identification was the large number of active compounds in the seized samples for which no reference vibrational data were available in the libraries rather than poor spectral quality. Therefore, when 33 of these compounds were independently identified by NMR and mass spectrometry and their spectra used to extend the libraries, the percentage of samples identified by IR and Raman screening alone increased to 76%, with only 7% of samples having no identifiable constituents. This study, which is the largest of its type ever carried out, therefore demonstrates that this approach of detecting non-matching samples and then identifying them using standard analytical methods has considerable potential in NPS screening since it allows rapid identification of the constituents of the majority of street quality samples. Only one complete feedback cycle was carried out in this study but there is clearly the potential to carry out continuous identification/updating when this system is used in operational settings.

Identification of new psychoactive substances (NPS) using handheld Raman spectroscopy employing both 785 and 1064 nm laser sources

“…Jones et al evaluated Raman spectra of NPS mixtures by subtracting the spectra of pure substances sequentially after identifying the substances using a Raman microscope. [38] Interestingly, the product Pink panthers (P56), which was confirmed to contain both 5,6-MDAI and MPA with GC-MS analysis correlated to 5,6-MDAI using the 785 nm source and to MPA using the 1064 nm source. This may be the result of mixture heterogeneity inherent to branded products, despite efforts to vortex mix.…”

“…In summary, no NPS ingredients were identified in the BZD products using the 'first pass' algorithm or by visual inspection of the spectra as the products were largely composed of excipients used for tablet and pellet construction (i.e., MCC and LAC), which was also observed in a recent study using a benchtop Raman spectrometer. [38] This indicates that for these BZDs and perhaps other NPS in tablet form, identification of the active ingredient can be challenging (i.e., resulting in false negatives), as the amount of active ingredient may be significantly lower relative to the excipients. The use of spectral subtraction is a possible tool for mixtures that may reduce these types of false negatives; it could be used to improve the identification of NPS with low content in the presence of larger amounts of cutting agents that results in a larger Raman signal than the NPS.…”

“…The use of spectral subtraction is a possible tool for mixtures that may reduce these types of false negatives; it could be used to improve the identification of NPS with low content in the presence of larger amounts of cutting agents that results in a larger Raman signal than the NPS. [38] …”

“…Bell and coworkers recently reported on the use of Raman spectroscopy for the identification of a range of NPS products using an λ ex of 785 nm. [38] From these studies, a challenge when using Raman to analyse NPS 'street samples' was fluorescence, often resulting from impurities and/or cutting agents, which can mask the signal from the active ingredients in the product. [31,39,40] Goodacre and coworkers investigated the use of surface enhanced Raman spectroscopy (SERS) to enhance the Raman signal while also reducing interference due to fluorescence.…”

“…[33] More recently, a number of studies have evaluated the use of Raman for NPS products. [32,[34][35][36][37][38] Maheux and Copland (2011) used a range of analytical techniques including Raman spectroscopy for the identification of cathinones in seized samples. [34] Studies also reported on the use of Raman spectroscopy to discriminate between cathinone regioisomers [35] and derivatives [32] using benchtop Raman instruments employing a laser excitation wavelength (λ ex ) of 785 nm.…”