|Year : 2019 | Volume
| Issue : 1 | Page : 29-32
Handheld raman spectrometer for the rapid determination of synthetic cannabinoids
Ling Zhang1, Guoping Li2
1 Dalian Muicipal Public Security Bureau, Dalian, China
2 Department of Criminal Technology, Liaoning Police College, Liaoning, China
|Date of Web Publication||28-Mar-2019|
Huangshan Road 1, Ganjingzi District, Dalian, Liaoning
Source of Support: None, Conflict of Interest: None
A handheld laser Raman spectrometer was developed to detect 11 synthetic cannabinoid standards. The spectrometer can be connected with a mobile phone by Bluetooth or a computer by a data cable. The Raman spectra of the synthetic cannabinoids AM-694, JWH-019, and nine others were accurately determined by software analysis of characteristic Raman peaks. This technique is highly efficient, accurate, and simple, and it is a valid procedure for rapid on-site investigations of cannabinoids.
Keywords: Cannabinoids, drugs, Raman spectrometry
|How to cite this article:|
Zhang L, Li G. Handheld raman spectrometer for the rapid determination of synthetic cannabinoids. J Forensic Sci Med 2019;5:29-32
| Introduction|| |
With the development and popularization of chemical synthesis technology in recent years, the number of new drugs is constantly increasing. Synthetic cannabinoids are new drugs that are rapidly replacing traditional cannabis in society because of their stronger effects. To curb the spread of these new drugs, some synthetic cannabinoids, including AM-694 and JWH-019, were listed as Class I psychotropic drugs in the catalog of psychotropic drugs in China on January 1, 2014. Effective methods are urgently needed to identify synthetic cannabinoids in criminal cases.
Usually, high-performance liquid chromatography or liquid chromatography–mass spectrometry is used for synthetic cannabinoid analysis. These techniques require complex instruments, are expensive, and are not suitable for on-site rapid testing and continuous online analysis. Therefore, a miniaturized handheld detector is needed. The Raman spectrum, which illustrates scattering intensities as a function of frequency shifts, depends on the rovibronic states of a molecule. When incident light irradiates the material surface, Raman spectra of different molecular structures can be obtained because of changes in molecular vibrations and rotational energy levels. Raman spectroscopy is commonly used in the biological sciences,, archeology, gem identification, and other disciplines. Many research groups have focused on miniaturization of the Raman spectrometer.
In this study, we developed a small (56 mm × 52 mm × 25 mm) and light (90 g) handheld Raman spectrometer. This device is convenient to carry and easy to operate. The spectrometer can be connected with a mobile phone by Bluetooth or a computer by a data cable. Raman spectra were acquired using the mobile phone or computer as shown in [Figure 1]. We investigated the influences of ambient light, the position of the excitation light, and plastic packaging on detection of 11 new synthetic cannabinoid standards, including AM-694 and JWH-019. The results were compared with those from an XPLORA Raman spectrometer.
| Materials and Methods|| |
A handheld laser Raman spectrometer with an excitation wavelength of 785 nm, spectrum image acquisition range of 300–2300 cm−1, and laser output power of 60–70 mW was constructed in our laboratory. We also used an XPLORA Raman spectrometer (Olympus Corporation, Tokyo, Japan) with an excitation wavelength of 785 nm, spectrum image acquisition range of 300–2300 cm−1, and laser output power of 150 mW.
All the 11 synthetic cannabinoid standards used in this article were purchased from the Shanghai Institute of Criminal Science and Technology (Shanghai, China) and listed in [Table 1].
| Results and Discussion|| |
Position of the excitation light
Selection of the focus location is particularly important for the accuracy of Raman spectrometry. For bulk solid samples, the fiber-optic probe can be placed directly on the surface. In this study, the powder samples were packed in thin plastic bags before analysis. Each sample was placed on an objective table we constructed in our laboratory. The distance between the sample and the excitation light fiber probe was optimized. Satisfactory Raman spectra were obtained with 4 mm between the fiber probe and the objective table.
Influence of ambient light
Ambient light conditions are very important in Raman spectroscopy. The Raman spectra of JWH-019 under different ambient light conditions are shown in [Figure 2]. With exposure to sunlight, many unknown peaks appeared at 400–500 cm−1 and the noise signals were very strong. In partial shade, the unknown peaks and noise signals were still present but were less intense. When the sample table was placed in a darkroom, the unknown peaks at 400–500 cm−1 were not obvious, the baseline was stable, and the target cannabinoid peak intensities greatly increased. Therefore, samples need to be analyzed in a darkroom for satisfactory results.
|Figure 2: Raman spectra of JWH-019 recorded under different ambient light conditions. (a) Sunlight, (b) partial shade, (c) darkroom|
Click here to view
Influence of plastic packaging
In normal conditions, the synthetic cannabinoids were often collected and found in plastic packaging. To be more convenient, the samples could be tested in plastic packaging directly, so it was necessary to investigate the effects of plastics with different specifications and made from different materials on the Raman results. Strong peaks between 1100 cm−1 and 1200 cm−1 were present for plastic packaging. Moreover, stronger signals were obtained with thick or darkly colored plastic compared to thin or lightly colored plastic. Therefore, 0.04-mm thick clear plastic was used to pack the sample powders.
| Comparison With Xplora Raman Results|| |
The results for the 11 new synthetic cannabinoid standards obtained under the optimized conditions using the handheld Raman spectrometer were compared with those from the XPLORA Raman spectrometer [Table 2]. There was good agreement between the results from the two instruments. The XPLORA Raman spectrometer has a stronger laser intensity and higher resolution than the handheld spectrometer, but it is not suitable for rapid on-site testing or continuous online analysis because of its operational complexity and rigorous testing conditions. By comparison, the handheld laser Raman spectrometer is smaller, lighter, easy to carry, and simpler to operate. Therefore, the handheld Raman spectrometer is a valid alternative for highly efficient, accurate, simple, and rapid on-site investigations of new synthetic cannabinoids.
| Conclusions|| |
We developed a handheld laser Raman spectrometer that is smaller, lighter, and easier to carry and operate than a traditional Raman spectrometer. In addition, the handheld Raman spectrometer provides nondestructive detection, rapid analysis, and similar accuracy to a traditional Raman spectrometer. The influence of ambient light, position of the excitation light, and plastic packaging, and their effects on results of the analysis were studied. Under the optimized conditions, 11 new synthetic cannabinoid standards, including AM-694 and JWH-019, were detected by the handheld Raman spectrometer. The results agreed with those from an XPLORA Raman spectrometer. The handheld Raman spectrometer provides a highly efficient, accurate, and simple method as a valid alternative for rapid on-site investigations of new synthetic cannabinoids.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]