Highly sensitive quantification of 12 drugs of abuse in wastewater using a simple dilution approach

Using the SCIEX Triple Quad 7500 system, powered by SCIEX OS software 

Sun Xiaojie1, Liu Bingjie1, Li Lijun1, and Guo Lihai1
1
SCIEX, Shanghai

Abstract

Measuring excreted drug residues in wastewater is a non-invasive approach to monitor drug consumption trends across a specific community or location. Here a combination of simplified sample preparation and high sensitivity mass spectrometry was applied to the study of drugs of abuse in wastewater surveillance. Quantification of 12 common drugs of abuse from wastewater using the SCIEX 7500 system was demonstrated, with good sensitivity (LLOQ of 1 pg/mL) and reproducibility. In addition, the MRM-triggered MS/MS capability of the QTRAP system enabled confident accurate identification of the analytes using spectral library searching.

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Introduction

Wastewater analysis is an alternative method of monitoring population drug consumption by measuring excreted drug residues in raw wastewater. Unlike toxicology analysis, the study of drugs of abuse and their metabolites in wastewater provides a non-invasive measure of geographical drug consumption while protecting individual’s anonymity. In addition, wastewater analysis provides a robust method of monitoring drug consumption trends across a specific community or location which could be subsequently relevant to identify new substance use and emerging hot spots of drug abuse. For these reasons, analysis of wastewater provides a robust drug market surveillance system comparable to traditional epidemiological approaches.

Generally, the residual concentration of drugs and their metabolites is relatively high and easily detectable in human excrement. However, following ingestion, the concentration of drugs and their metabolites in human excrement is diluted significantly in wastewater. As a result, the analytical sensitivity needed for the analysis of drugs and their metabolites in sewage water is much higher than the requirements for general biological materials commonly screened by conventional toxicology approaches. By the time water sampling occurs at the wastewater treatment plan, drugs and their residuals are found in extremely low (sub ppm to ppt) levels. As a result, there is a need for rapid and robust drug screening methods capable of accurately quantifying drugs of abuse and their metabolites with a high level of selectivity and sensitivity.

In this technical note, the sensitivity of the SCIEX 7500 system1 was investigated for the detection of 12 drugs of abuse in wastewater. To this end, sub-pg/mL levels of drugs and metabolites were accurately detected with high quantitative metrics (accuracy, precision, linear response) even with a simple dilution approach. 

Figure 1. Accurate identification of cocaine using the QTRAP system functionality of the SCIEX 7500 system. Extracted ion chromatogram (XIC) and MS/MS spectrum showing confident identification of cocaine in one of the wastewater samples. MRM XIC provides quantitative data and the full scan MS/MS is matched to the library spectrum for confident confirmation.

Key advantages of the SCIEX Triple Quad 7500 system for sensitive detection of THC-COOH in oral fluid

  • Hardware improvements on the SCIEX 7500 system provide significant gains in sensitivity and quantitative performance1
  • Instrument sensitivity is leveraged to streamline and simplify sample preparation, negating the need for laborious, costly and time-consuming sample cleanup techniques such as online or offline solid-phase extraction (SPE)
  • Improved ion generation and sampling on the SCIEX 7500 system enables accurate and sensitive quantification of all 12 drugs of abuse down to sub-pg/mL levels 
  • The ion trap functionality of the SCIEX 7500 system was leveraged to perform simultaneous identification and confirmation of drugs using the full scan MS/MS data and automated MS/MS library searching
  • The results highlight the impressive levels of sensitivity, robustness and accuracy provided by the SCIEX 7500 system for wastewater drug monitoring