Pharmaceutical Uptake in Radish Plants at Local Environmental Concentrations: Insights from LC-MS/MS and MALDI-MS

Pharmaceuticals are contaminants of emerging concern due to their incomplete removal in wastewater treatment plants, leading to measurable concentrations in the environment. These compounds are currently not regulated as environmental contaminants; therefore, the effect of pharmaceuticals on the ecosystem has been minimally studied. Because the main source of pharmaceuticals in the environment is through wastewater effluent, samples from four local wastewater treatment plants were collected and analyzed. Two samples from each site were filtered before an acidification or basification step, followed by solid phase extraction with Oasis HLB 6 mL/200 mg cartridges. Extracted samples were analyzed on a Shimadzu LCMS 8060NX triple quadrupole. Before sample analysis, multiple reaction monitoring (MRM) optimization was completed on 26 different pharmaceutical compounds including statins, beta blockers, antidepressants, and antibiotics. All pharmaceuticals were detected in at least one of the sites, with eleven detected at every site. Because toxicological effects are difficult to parse when organisms are exposed to numerous compounds simultaneously, the contaminant with the highest average concentration found in the effluent samples, metoprolol, was selected to investigate uptake in plants. Radish plants were selected as a model plant due to their quick growth and sizable root structures allowing for measurements to be made in roots and leaves. Radishes were dosed with the environmental concentration, as well as 10 and 100 times the same concentration over a 28-day exposure period using a bottom-watering technique. Lyophilization and QuEChERS extractions were performed on the leaves at different time points in the exposure, prior to LC-MS/MS analysis. Preliminary data showed uptake of metoprolol into radish leaves at all exposure levels. Additionally, sections from roots and leaves were analyzed with MALDI-MS to determine localization of contaminants within the tissues.