Identification of a New Antidepressant and its Glucuronide Metabolite in Water Samples Using Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry

Abstract

This paper reports the first detections of an antidepressant, lamotrigine, and its major metabolite (2-N-glucuronide), in environmental water samples using a new chlorine mass-filter technique with accurate mass and high resolution. A quantitative method is described using solid phase extraction (SPE) followed by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF-MS) for the simultaneous analysis of both compounds in aqueous samples, including drinking water, groundwater, surface water, and wastewater collected from sewage treatment plants. The recoveries of the analytes ranged from 75 to 99%, depending on the type of water extracted. The method detection limits were 1 and 5 ng/L for lamotrigine and its metabolite, respectively. The method was validated with more than a hundred aqueous samples analyzed and lamotrigine and its 2-N-glucuronide metabolite were mostly detected in both wastewater and surface water impacted sites at mean concentrations of 488 and 209 ng/L, respectively. Lamotrigine was detected in 94% of all the wastewater samples analyzed. Two detections for lamotrigine occurred in drinking water. To our knowledge, this is the first report of water samples containing lamotrigine, a relatively new drug used for the treatment of epilepsy and type I bipolar syndrome. It is also the first report of a glucuronide of an antidepressant surviving wastewater treatment plant operations and becoming a ground and surface water contaminant.