Detection of Mitragynine in Mitragyna Speciosa (Kratom) Using Surface‐Enhanced Raman Spectroscopy with Handheld Devices

Abstract

A simple, quick, selective, sensitive, and effective field‐friendly method capable of being used by nonexperts has been developed for detecting mitragynine in Mitragyna speciosa (kratom) using surface‐enhanced Raman spectroscopy (SERS). Over 100 samples and blanks (known to be either positive or negative for the presence of mitragynine) were examined in duplicate using five identical handheld Raman spectrometers, which provided a data set of over 1,000 examinations. Based on the results of these analyses, the method yielded a true‐positive rate of 99.3%, a true‐negative rate of 97.9%, a false‐positive rate of 2.1%, and a false‐negative rate of 0.7%. The average minimum detectable concentration (Cm) of mitragynine that reproducibly yielded a match for one of the library spectra on all five instruments was determined to be 342 ng/mL (ppb). This Cm value is a conservative estimate considering that the extraction process was not fully optimized by this study, which was not necessary since the Cm value achieved was well below typical mitragynine concentrations in kratom (1.3–2.3%). The method is ideal (i) for prioritizing samples for additional testing using other more time‐consuming laboratory‐based techniques needed to detect and quantify mitragynine and (ii) for field use at international mail facility (IMF) satellite laboratories to help interdict kratom and prevent this dangerous product from reaching the U.S. supply chain.

Rapid determination of eight benzodiazepines in suspected counterfeit pharmaceuticals using surface‐enhanced Raman scattering with handheld Raman spectrometers

“…Samples were first prepared for SERS analysis by extracting the benzodiazepines in tablets and capsules using 10% MeOH in water diluent followed by addition of Ag colloids and aggregating agent. This method has been successfully demonstrated by our group to be effective in detecting a wide range of analytes [24][25][26]. If suitable results were not achieved for a given sample using this method, the sample was prepared for SERS analysis by separating the benzodiazepine of interest from tablet or capsule using 10% ammoniated chloroform followed by addition of 1 N HCl and Au colloids.…”

“…Additionally, all the SERS spectra of the reference standards used Ag colloids solutions with exception of clonazepam, diazepam, and temazepam, which used Au colloids. The SERS signature collection data revealed that APIs in their free base form resulted in better spectral features using Ag colloids and KBr salt [24][25][26] while those in their HCl salt form had enhanced spectral features with Au colloids and LiCl salt [36].…”

“…Consequently, we have developed several surface-enhanced Raman scattering (SERS) methods using these handheld devices to lower detection limits and increase the number of APIs that can be detected [24][25][26]. These methods have been used along with other analytical devices at a satellite laboratory stationed outside the IMF in Chicago during a three-month pilot program and will soon be used at the same location when the project transitions to a full operational mode [27].…”

“…However, when used under normal operating conditions, these devices have been less effective for identifying low‐concentration APIs in finished dosage forms due to the characteristic low sensitivity of Raman spectroscopy. Consequently, we have developed several surface‐enhanced Raman scattering (SERS) methods using these handheld devices to lower detection limits and increase the number of APIs that can be detected [24–26]. These methods have been used along with other analytical devices at a satellite laboratory stationed outside the IMF in Chicago during a three‐month pilot program and will soon be used at the same location when the project transitions to a full operational mode [27].…”

Trace level detection of select opioids (fentanyl, hydrocodone, oxycodone, and tramadol) in suspect pharmaceutical tablets using surface‐enhanced Raman scattering (SERS) with handheld devices

“…The FDA plans to foster its enforcement actions by collaborating with Customs and Border Protection (CBP), by increasing the num- [8,9]. This structural information obtained using SERS [10] is used to reliably screen and detect APIs in finished dosage tablets [11], in bodily fluids [12][13][14][15] and in ground plant powder [16]. Additionally, Raman spectrometers have been miniaturized into handheld devices that are rugged, robust, and easily portable, making them ideal for IMFs and ECHs where space is often limited.…”