Elsevier

Talanta

Volume 234, 1 November 2021, 122627
Talanta

Quantification of selected analgesics and their metabolites in influent wastewater by liquid chromatography tandem mass spectrometry

https://doi.org/10.1016/j.talanta.2021.122627Get rights and content

Highlights

  • Validated LC-MS/MS method for 35 analgesics and associated metabolites in wastewater.

  • Extraction recoveries between 80% and 120%.

  • 28 analgesics and metabolites quantified in wastewater.

  • Population normalised mass loads of paracetamol and ibuprofen carboxylic acid highest.

  • Wastewater-based surveillance of community analgesics uses now achievable.

Abstract

Wastewater-based epidemiology (WBE) is an established tool to analyse patterns of community drug use. In recent times, monitoring the use of analgesics has become a public health priority. An analytical method was developed, optimised and validated for a broad range of common analgesics (non-steroidal anti-inflammatories and opioids) and their metabolites at trace concentrations in wastewater influent. Samples were analysed via liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with an electrospray ionization source (ESI) in both positive and negative ion multiple reaction monitoring modes. Fifteen of the thirty-five biomarkers were validated for LC-MS/MS analysis by direct injection, while the other 20 biomarkers were present in wastewater at lower concentrations, requiring extraction by solid phase extraction (SPE) using Oasis HLB cartridges. The limit of quantification (LOQ) ranged between 17 ng/L - 191 ng/L and 13 ng/L −110 ng/L for direct injection and SPE, respectively. Recoveries for SPE ranged between 80% and 120%. Following validation, the method was applied to 28 wastewater samples from four municipal wastewater treatment plants. Twenty-eight of the thirty-five analgesic biomarkers were detected in the samples at concentrations of between 0.03 and 289 μg/L. Population normalised mass loads ranged from 10 mg/day/1000 (meperidine) to 72,000 mg/day/1000 (paracetamol) among all investigated compounds. The described method is a suitable analytical tool for wastewater-based epidemiology applications to estimate analgesics consumption.

Introduction

Pain is a growing global health concern. Worldwide, one in five adults suffers from pain, and one in ten patients is diagnosed with chronic pain every year [1]. Pain is one of the main reasons individuals seek medical treatment [2]. Analgesics are used to relieve pain experienced in the body. They can be classified into non-steroidal anti-inflammatory drugs (NSAIDs) and opioids. NSAIDs produce their analgesic effect through inhibition of cyclooxygenase (COX) whereas opioids produce analgesia through the activation of opioid receptors [3].

Measuring the use of pain drugs and integrating knowledge on multiple types of pain medications can be used as a proxy for the treatment of pain burden in communities. Wastewater-based epidemiology (WBE) provides the opportunity to measure community consumption of substances and has been extensively applied to illicit drugs [[4], [5], [6]]. NSAIDs and opioids are metabolised by the body and excreted via urine or feces as the parent drug and metabolites, eventually ending up in the sewer network and sewage treatment plants. Subsequently, wastewater samples can be used as a source of pooled urine and feces that contains information about a population's chemical consumption and exposure [7]. The information is acquired from the chemical analysis of specific human excreted biomarkers in wastewater that can be used to estimate per capita consumption for studied catchment populations.

Quantification of biomarkers in wastewater is challenging. Advanced instrumentation, such as, liquid chromatography-mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS/MS) are the standard approaches used to selectively quantify biomarkers in wastewater. To date, published methods that quantify consumption of several opioids or occurrence of NSAID drugs in wastewater comprised mainly of a reconcentration and purification step based on solid-phase extraction (SPE) and later analysis by LC-MS/MS. These methods focus on the determination of a limited number of opioids and/or NSAIDs and their metabolites in wastewater in conjunction with other drugs of interest [5,[8], [9], [10], [11], [12], [13]]. There is at present no suitable analytical method capable of measuring a broad range of analgesic drugs and their metabolites simultaneloulsy at low level (ng/L) in wastewater. Such a method could be used to reveal a more comprehensive understanding of the different levels of pain treatment applied in communities [14].

This study aimed to develop and validate a novel analytical method to quantify the most commonly used analgesics and their metabolites in wastewater. The method was applied to wastewater influent samples collected from four different municipal wastewater treatment plants (WWTPs) across Australia. The validated method can serve as an analytical tool to estimate the treated pain burden through WBE.

Section snippets

Target analytes

The analysis herein includes the most consumed analgesic in Australia and their metabolites in wastewater according to Australian Pharmaceutical Benefits Scheme (PBS) database [15]. Among the NSAIDs, ibuprofen carboxylic acid/carboxyibuprofen, salicylic acid, diclofenac, parecoxib, valdecoxib, celecoxib, etoricoxib, indomethacin, ketoprofen, piroxicam, paracetamol, pregabalin, amitriptyline, gabapentin, naproxen, and their corresponding isotope-labelled internal standards were included (full

Solid phase extraction (SPE) optimisation

To optimise the recovery of studied compounds, several SPE sub-method steps were trialled (Table 1). In these SPE trials, only Oasis HLB (3 cc/60 mg) cartridges were used. Sample pre-treatment procedures and sample pH were similar in all trials. Different wastewater volumes (10 or 50 mL) were used and different concentration washing solvents were also employed. Different concentrations of formic acid in the elution solvent with methanol were also trialled and later all samples were fully

Conclusions

A selective and sensitive analytical method based on direct injection and SPE extraction was developed and validated for a broad range of NSAIDs and opioids and their biomarkers in wastewater influent. The method offers a low volume wastewater samples to use and a simple SPE extraction procedure. The method meets the performance ICH guideline criteria and was tested on real wastewater samples which also proved the applicability to detect 28 of the 35 analgesics and their metabolites in

Declaration of competing interest

The authors have no conflict of interest to declare.

Acknowledgements

The Queensland Alliance for Environmental Health Sciences, The University of Queensland, gratefully acknowledges the financial support of the Queensland Department of Health. Fahad Ahmed is the recipient of The University of Queensland Research Training Scholarship and a QAEHS Research Higher Degree Top-Up Scholarship.

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