A sensitive analytical method for the measurement of neurotransmitter metabolites as potential population biomarkers in wastewater.

Wastewater-based epidemiology is a growing research field which provides valuable information on community drug use and chemical exposure. One parameter critical to estimations of drug use is the catchment area population. A population biomarker could be used to provide this information. This study evaluated the analytical suitability of three endogenous biomarkers of human activity: the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) which has previously been proposed and two further candidates, the catecholamine metabolites vanillylmandelic acid (VMA) and homovanillic acid (HVA). An analytical method involving derivatization was developed and validated for two candidates, 5-HIAA and HVA by liquid chromatography - mass spectrometry. The best performance was obtained for VMA as the underivatized analyte. The derivatized extracts produced a 100 times better sensitivity. The three neurotransmitter metabolites were evaluated as population biomarkers in wastewater samples. All were stable in sample, not lost upon filtration and showed stable inter-day mass loads over seven days for a metropolitan wastewater treatment plant. When applied to a small community during a festival period, mass loads of both HVA and VMA reflected the increase in the catchment population, whilst 5-HIAA proved to be more variable.