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

Abstract The excessive prescription of benzodiazepines is putting more people at risk of dependence on these drugs and is exacerbating the fatal overdose toll of opioids. A rapid and sensitive SERS method has been developed for trace detection of select benzodiazepines in low‐dosage suspect counterfeit tablets, capsules, and injectable solutions using two different portable handheld Raman spectrometers equipped with either a 785‐nm laser or a 1064‐nm laser. A total of 169 samples and blanks were examined using five handheld Raman spectrometers, which provided data set of 729 examinations. The extraction/SERS procedures yielded true positive rates above 90% for alprazolam, diazepam, and midazolam using the 1064‐nm device and yielded true positive rates above 95% for alprazolam, clonazepam, diazepam, estazolam, midazolam, and temazepam using the 785‐nm device; however, the extraction/SERS procedures yielded true positive rates below 60% for lorazepam and triazolam. The minimum concentration ( C min ) of the benzodiazepine standards that reproducibly yielded a positive match ranged from 1 to 10 μg/ml using the 1064‐nm laser device and from 0.5 to 50 μg/ml using the 785‐nm laser device. For the analysis of authentic and suspect counterfeit tablets containing these benzodiazepines, the measured C min ranged between 10 and 15 µg per tablet or capsule for 1064‐nm laser device and 1–100 µg per tablet or capsule for 785‐nm laser device. The developed methods are simple, rapid, and ideal for screening suspect benzodiazepine‐containing pharmaceutical products at satellite laboratories located within or near international mail facilities and express courier hubs.