Quantification of Caffeine as an Anthropogenic Marker in Western Lake Superior

Abstract

Caffeine (1,3,7-trimethylxanthine) is a widely used anthropogenic marker to trace untreated wastewater in natural water samples. Understanding possible locations of wastewater inputs and the extent to which contaminants in untreated wastewater can spread is significant in maintaining and preserving Lake Superior’s ecosystems and water quality. For this study, an existing method based on solid phase extraction using hydrophilic-lipophilic-balanced (HLB) resin and electrospray mass spectrometry was revised and applied to quantify the caffeine content in western Lake Superior. Method development addressed sample preparation techniques, determinations of the limits of detection and quantification of caffeine, and quantitative analysis for analyte ion fragmentation. Once the method was optimized for analyte quantification, western Lake Superior surface water samples were collected at 5 stations, including off and near shore sites, to gain insight into possible contaminant distributions. Caffeine measurements ranged from 5-26 ng/L with higher concentrations near shore and depleted concentrations offshore.