Analysis of illicit drugs and pharmaceuticals in edible seaweeds by liquid chromatography-tandem mass spectrometry

Drugs taken by humans and animals can end up in the hydrosphere. Bioaccumulation of drugs in aquatic plants and animals may have biological consequences and could provide a route for human exposure through dietary consumption. A robust and reproducible method using liquid extraction and HPLC coupled tandem mass spectrometry (LC-MS/MS) was developed and applied for the first time to measure illicit, behavioral and antihistamine drugs in edible seaweeds. Target analytes were identified by their product ion spectra and retention times, and quantified using mass labeled internal standards. Recoveries of target analytes ranged from 69.3 to 110.2% with relative standard deviations (RSDs) of 1.5-12.0%. The method detection limits (MDLs) for seven compounds ranged from 0.06 to 3.51 ng g⁻¹. Average surrogate recoveries were 67 to 106% with 3 to 8% RSD. We detected two illicit drugs cocaine and methadone, and two behavioral medicines carbamazepine and diazepam. Levels of cocaine, methadone, carbamazepine and diazepam in the edible seaweeds studied were 82.9-274.8, 9.6-36.7, 5.0-5.9, and 3.4-12.4 ng g⁻¹, respectively.