Investigating in-sewer transformation products formed from synthetic cathinones and phenethylamines using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

Abstract

Recent studies have demonstrated the role of biofilms on the stability of drug residues in wastewater. These factors are pertinent in wastewater-based epidemiology (WBE) when estimating community-level drug use. However, there is scarce information on the biotransformation of drug residues in the presence of biofilms and the potential use of transformation products (TPs) as biomarkers in WBE. The purpose of this work was to investigate the formation of TPs in sewage reactors in the presence of biofilm mimicking conditions during in-sewer transport. Synthetic cathinones (methylenedioxypyrovalerone, methylone, mephedrone) and phenethylamines (4-methoxy-methamphetamine and 4-methoxyamphetamine) were incubated in individual reactors over a 24h period. Analysis of parent species and TPs was carried out using liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QToFMS). Identification of TPs was done using suspect and non-target workflows. In total, 18 TPs were detected and identified with reduction of β-keto group, demethylenation, demethylation, and hydroxylation reactions observed for the synthetic cathinones. For the phenethylamines, N- and O-demethylation reactions were identified. Overall, the experiments showed varying stability for the parent species in wastewater in the presence of biofilms. The newly identified isomeric forms of TPs particularly for methylone and mephedrone can be used as potential target biomarkers for WBE studies due to their specificity and detectability within a 24h residence time.

Development of non-target screening workflows for the identification of biotransformation products of emerging pollutants in wastewater by mass spectrometric techniques

“…Therefore, only 60% of PMMA was (bio)transformed as the sorption and abiotic reactors were used to account for losses through abiotic processes. It is likely that PMMA has a higher rate of degradation in an activated sludge reactor as a previous study involving in-sewer incubation of PMMA in the presence biofilm had 20% loss over 24 h incubation [104]. Two TPs were detected and identified (TP-166 and TP-196) in the biotic reactor (Table 4.3).…”

“…In some studies mephedrone levels in wastewater have been reported as below quantification level or absent [106,107,109], more likely due to its significant (bio)transformation under aerobic conditions in-sewer system, as it has been reported [104,113,114]. Additionally, DHM was identified as a major TP from an in-sewer stability experiments and determined to be a reliable biomarker due to its levels within a 24 h residence time [104]. Though DHM has not been monitored in wastewater studies it has been proposed as a biomarker of exposure for mephedrone use in wastewater based epidemiology [104] and has been previously detected in pooled urine samples from UK [115].…”

“…Several studies have investigated the presence of mephedrone in wastewater [106][107][108][109][110][111][112]. In some studies mephedrone levels in wastewater have been reported as below quantification level or absent [106,107,109], more likely due to its significant (bio)transformation under aerobic conditions in-sewer system, as it has been reported [104,113,114]. Additionally, DHM was identified as a major TP from an in-sewer stability experiments and determined to be a reliable biomarker due to its levels within a 24 h residence time [104].…”

“…Previous studies have investigated the presence of PMMA in influent wastewater to determine community use [102,103], however, PMMA levels have been reported as very low only [103]. In-sewer stability of PMMA in the presence of biofilm has been reported as stable [104,105] within 24 h indicating it is stable before WW treatment processes.…”

“…Additionally, DHM was identified as a major TP from an in-sewer stability experiments and determined to be a reliable biomarker due to its levels within a 24 h residence time [104]. Though DHM has not been monitored in wastewater studies it has been proposed as a biomarker of exposure for mephedrone use in wastewater based epidemiology [104] and has been previously detected in pooled urine samples from UK [115].…”