Identify and Differentiate Fentanyl vs. Carfentanil with Amplifi ID
The fast and reliable detection of potent synthetic opioids like fentanyl and carfentanil is crucial for effectively tackling the opioid crisis. Fentanyl belongs to a group of drugs known as fentanyl analogs (or "fentalogs"), which are fast-acting synthetic opioids that relieve pain without causing loss of consciousness.​ [1] ​ Carfentanil, a fentanyl analog, is about 100 times more potent than fentanyl and roughly 10,000 times stronger than morphine. [2]​​ Both fentanyl and carfentanil work by binding to opioid receptors in the brain, which are involved in the regulation of pain and emotions. [3] The extreme potency of carfentanil means that even tiny, grain-sized amounts can result in a fatal overdose, and naloxone treatment for carfentanil overdoses may require many more doses than for a typical fentanyl overdose. Quick and precise detection of opioids is vital for preventing overdoses; however, it’s not enough to only identify the presence of an opioid—it's also important to distinguish between different opioids to provide actionable prevention and response, such as administering enough naloxone in a carfentanil overdose.
Image 1. Estimated lethal dose of each drug. Image source: bostonglobe.com.
Due to the high potency of opioids like carfentanil, the analytical method used must have high sensitivity to detect these substances at low levels and sufficient specificity to distinguish them from fentanyl and other analogs. Street samples containing fentanyl may vary in amount, from a small fraction of a percent up to 75% mass percent concentration (w/w) of the sample, while those with carfentanil usually contain only 0.01% to 0.02% (w/w). [4] These concentration ranges make common drug testing techniques, such as Infrared Spectrometry (FTIR) and standard Raman spectroscopy, inadequate for detecting and identifying these fentanyl analogs in street drugs, due to their detection limits of 5-10% (w/w). Although fentanyl test strips (FTS) are useful for detecting fentanyl presence, they cannot differentiate between different analogs. [5] These strips do not indicate whether a sample contains carfentanil rather than fentanyl. Surface-Enhanced Raman Spectroscopy (SERS), a vibrational spectroscopy method, provides a rapid and accurate approach by analyzing the molecular vibrational signatures, allowing detection and differentiation even at low concentrations.
The Science Behind Amplifi ID: Chemical Fingerprinting with Raman Spectroscopy and SERS
Standard Raman and SERS employ the principle that each molecule exhibits a unique vibrational fingerprint based on its molecular structure, functional groups, and chemical bonds to distinguish between analytes. In the case of fentanyl analogs, even slight structural modifications, such as alterations in functional groups or substitution patterns, may generate distinct vibrational signatures and influence pharmacological properties. For example, carfentanil possesses a carboxylate ester functional group absent in fentanyl, as illustrated in Figure 1.
Figure 1. 2D molecular structure representation of a) Fentanyl and b) Carfentanil. Most fentanyl analogs share the same structure backbone with subtle structural modifications, such as the carboxylate ester functional group, which is absent in fentanyl.
These structural differences are reflected in the Raman and SERS spectra through variations in peak presence or absence, peak shape, or peak ratios, as demonstrated in Figure 2, where the primary spectral regions of interest (ROI) for fentanyl are highlighted in blue, those for carfentanil in red, and the shared regions are shaded grey.
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b)
Figure 2. a) Bulk Scans (standard Raman) signals of powder reference standard fentanyl and carfentanil. b) Trace Scans (SERS) of laboratory reference standards from Fentanyl (200 ppm) and Carfentanil (200 ppm). The subtle structural modifications can produce distinct vibrational patterns. In this case, the predominant spectral regions of interest for fentanyl are highlighted in blue, for carfentanil highlighted in red, and the regions shared by both are highlighted in grey.
Identifying Carfentanil via Real-World Drug Analysis
The Amplifi ID Drug Checking System is a real-time, portable tool designed for street drug analysis and intelligence gathering. It provides rapid and easily interpretable results, enabling personnel to make informed decisions and efficiently collect data to address the overdose crisis. [6] The Amplifi ID system combines Standard Raman spectroscopy (Amplifi ID Bulk Scan mode) with SERS (Amplifi ID Trace Scan mode), employing advanced signal processing and identification algorithms to improve on-site detection of hazardous substance mixtures. The system's signal amplification significantly enhances spectral sensitivity, allowing the Amplifi ID to accurately differentiate fentanyl from chemically similar substances such as carfentanil, even at trace levels. This capability exceeds the detection thresholds of traditional vibrational spectroscopy, which typically range from 5% to 10% (w/w), achieving detection limits as low as 5 parts per million (ppm) through SERS technology.
Image 2: Amplifi ID Reader with a Trace Scan test cartridge inserted.
Figure 3. Raman signal comparison between laboratory standard 5 ppm carfentanil trace scan (red), real-world sample 1 with detection of carfentanil and xylazine (blue), and real-world sample 2 with detection of carfentanil and fentanyl (black). The predominant spectral regions of interest for carfentanil are highlighted in red.
In real-world samples, even minimal quantities of carfentanil can prove to be lethal. Figure 3 compares the SERS spectra of a laboratory-prepared 5 ppm carfentanil standard with two complex, real-world samples. The red bands highlight the predominant spectral ROI of carfentanil. The detection of identifiable features within this ROI for both the reference standard and the real samples provides reliable evidence of carfentanil presence across all three spectra. The laboratory sample distinctly exhibits characteristic carfentanil peaks, even when compared with higher concentrations (see Figure 2), thereby confirming the high sensitivity of Amplifi ID’s Trace Scan technology.
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In the analysis of real-world samples, both carfentanil and xylazine were identified in sample 1, while carfentanil and fentanyl were identified in sample 2. This affirms the technology's efficacy in detecting hazardous substances, including fentanyl analogs, within complex mixtures. Consequently, this underscores the significance of the Amplifi ID Drug Checking System as a vital instrument in the effort to combat the toxic drug supply. Our continuously expanding substance library enables the detection of high-risk compounds like carfentanil at low concentrations, providing essential early warnings to communities and supporting quick, informed responses to emerging threats.
References
1. Fentanyl: Incapacitating Agent | NIOSH | CDC.
3. Fentanyl | National Institute on Drug Abuse (NIDA).
4. Sified, U. CY 2021 Fentanyl Seizures-Powders Average Fentanyl Powder Purity by Seizure Size-CY 2021 Synthetic Route Determined for Fentanyl Powders-CY 2021 Fentanyl Powder Purity Distribution-CY 2021 Fentanyl Purity (%).
5. Limitations of test strips to check illegal drugs for dangerous substances - Canada.ca.