Abstract
Detection of illicit drug residues from wastewater provides a new route toward community-level assessment of drug abuse that is critical to public health. However, traditional chemistry analytical tools such as high-performance liquid chromatography in tandem with mass spectrometry (HPLC-MS) cannot meet the large-scale testing requirement in terms of cost, promptness, and convenience of use. In this article, we demonstrated ultra-sensitive and portable surface-enhanced Raman scattering sensing (SERS) of fentanyl, a synthetic opioid, from sewage water and achieved quantitative analysis through principal component analysis and partial least-squares regression. The SERS substrates adopted in this application were synthesized by in situ growth of silver nanoparticles on diatomaceous earth films, which show ultra-high sensitivity down to 10 parts per trillion in artificially contaminated tap water in the lab using a commercial portable Raman spectrometer. Based on training data from artificially contaminated tap water, we predicted the fentanyl concentration in the sewage water from a wastewater treatment plant to be 0.8 parts per billion (ppb). As a comparison, the HPLC-MS confirmed the fentanyl concentration was below 1 ppb but failed to provide a specific value of the concentration since the concentration was too low. In addition, we further proved the validity of our SERS sensing technique by comparing SERS results from multiple sewage water treatment plants, and the results are consistent with the public health data from our local health authority. Such SERS sensing technique with ultra-high sensitivity down to sub-ppb level proved its feasibility for point-of-care detection of illicit drugs from sewage water, which is crucial to assess public health.
Highlights
The prevalence of drug abuse and the epidemic level of opioid misuse urgently calls for a comprehensive approach to assess trends in drug abuse and understand the effectiveness of prevention and treatment programs
We developed a scattering sensing (SERS) substrate using in situ growth high-density AgNPs on diatomaceous earth and measured fentanyl residual signals using a portable Raman spectrometer to prove the feasibility of sewage water sensing
We provided a SERS spectrum of fentanyl in deionized water in Supplementary Materials Section 3
Summary
The prevalence of drug abuse and the epidemic level of opioid misuse urgently calls for a comprehensive approach to assess trends in drug abuse and understand the effectiveness of prevention and treatment programs. High-performance liquid chromatography in tandem with mass spectrometry (HPLC-MS) [7,8,9,10,11] is the most widely used wastewater sensing technique, which can detect various drugs including opioids in the wastewater stream and can differentiate between drugs that were discarded and drugs that were metabolized Such extraordinary analytical techniques can be adopted to address practical questions and dynamic monitoring of illicit drug use. Compared with other drug sensing methods, SERS techniques can provide exclusive advantages including ultra-high sensitivity [27,28,29], high specificity [30,31], easy sample preparation, low cost, and rapid testing. Our diatomaceous earth SERS substrate with a portable Raman spectrometer showed exceeding performance in terms of sensitivity, sensing time, and cost
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