New qualitative analysis strategy for illicit drugs using Raman spectroscopy and characteristic peaks method

Abstract

Performing fast qualitative identification of seized illegal drugs by Raman spectroscopy is challenging due to fluorescence interference as well as chemical complexity. Spectrometers with 785‐nm excitation, 1,064‐nm excitation, and sequentially shifted excitation (SSE) were compared for their effect on fluorescence reduction. The characteristic peaks method, which is independent of cutting agents, was tested as a new strategy to broaden the application of the Raman technique. The suitability of the characteristic peaks method was fully examined by analyzing a large amount of seized illegal drugs, including 72 methamphetamine hydrochloride (concentration range of 13.9%–99.4%), 68 ketamine hydrochloride (17.7%–99.8%), 176 heroin hydrochloride (5.2%–79.5%), 51 cocaine hydrochloride (21.1%–94.5%), and 33 cocaine base (30.9%–92.5%) samples. The results showed that seized methamphetamine, ketamine, and cocaine samples had no or little fluorescence. Hence, in regard to detection of these samples, the advantage of using 1,064‐nm excitation and SSE compared with 785‐nm excitation was quite limited. Regarding the heroin samples, a significant improvement of the “high” confident positive detected rate was evident for 1,064 nm excitation (60.8%) and SSE (61.4%), compared with 785‐nm excitation (13.1%). However, it was also seen that even if 1,064‐nm excitation and SSE were applied, the fluorescence of heroin samples was still unable to be fully overcome. By using the characteristic peaks method, low LOD results of 5%–20% were acquired for 40 types of drug mixtures, and lower LODs were obtained for the 60% of the drug mixtures compared with library searching method. Raman spectroscopy in conjunction with the characteristic peaks method was shown to be fast, simple, accurate, and sensitive in the qualitative analysis of seized drug samples.

Innovative Vibrational Spectroscopy Research for Forensic Application

“…Liu et al found that, while it may not be required in all situations, using a 1064 nm laser or sequentially shifted excitation (SSE) quite improved the analysis of heroin samples. 241 When compared to the 785 nm laser, positive identification increased almost 5-fold for both the 1064 nm laser and SSE. Kay et al addressed the same issue with a new technique known as Swept Source Raman Spectroscopy (SSRS).…”

“…One obstacle that can be encountered when analyzing evidence with a 785 nm excitation laser is background fluorescence. Liu et al found that, while it may not be required in all situations, using a 1064 nm laser or sequentially shifted excitation (SSE) quite improved the analysis of heroin samples . When compared to the 785 nm laser, positive identification increased almost 5-fold for both the 1064 nm laser and SSE.…”

Point-of-care community drug checking technologies: an insider look at the scientific principles and practical considerations

“…Studies have shown, for example, that for cocaine the limit of detection can range from 10% when cut with inositol to 40% when cut with paracetamol [ 85 ]. In another study, the LOD for heroin in a mixture was found to be as low as % [ 86 ].…”

Competitive fluorescence immunoassay for the rapid qualitative screening and accurate quantitative analysis of ketamine

“…Although these techniques offer excellent accuracy and sensitivity, they also display some disadvantages, including lack of portability, long test times, cumbersome and solventconsuming sample preparation steps, the need for skilled operators, high operation and maintenance costs, and nonsuitability for on-site analyses. Other commonly used methods included capillary electrophoresis, 28,29 uorescence immunoassay (FIA), 30,31 electrochemical methods, 32,33 surface plasmon resonance (SPR), 34 Raman spectroscopy, [35][36][37] and infrared spectroscopy (IR). [38][39][40][41] Among them, capillary electrophoresis has high separation efficiency but shows the same disadvantages as chromatography.…”