Caffeine as a tracer for sewage contamination in fresh water bodies
Student name: Ms Divya Gupta
Guide: Dr Arun Kansal
Year of completion: 2011
Host Organisation: Yale School of Forestry and Environmental Studies, Yale University
Supervisor (Host Organisation): Prof Gaboury Benoit
Abstract: A method based on Solid Phase Extraction (SPE) coupled to Gas Chromatography and Mass
Spectrophotometer has been applied to determine trace quantities of caffeine (1,3,7-
trimethylxanthine) in surface water samples from the West River and its tributaries, New haven,
Connecticut, USA. The aim behind the development of such method is to evaluate the use of
unmetabolized caffeine as a tracer of domestic sewage contamination. The method followed
allows the determination of caffeine at levels as low as 6ppt or 6ng/l in the West River
tributaries, whereas West River shows the caffeine level as high as 160ng/l. The samples
collected from the sites were filtered using GC/F glass filters of pore size 1.2micron and then
extracted approx. 1litre through the SPE and finally run on GC/MS operated at splitless injection
in selected ion monitoring (SIM) mode. SPE method is set up by using different eluting solvents,
wash solvents and cartridges/ disks. Cartridges worked over disks as disks showed poor recovery
of caffeine as compared to cartridges. Similarly, acetone worked over methanol and
dichloromethane as an eluting solvent in regards to recovery of caffeine through cartridges.
Washing solvent used is deionized distilled water which results in good recovery results as
compared to 5% methanol in deionized water. Blanks (deionized distilled water) were filtered
through the GC/F filters to assure that there is no contamination and then extracted similarly
through the SPE, finally run on GC/MS and analyzed that there is no caffeine in blanks. This
proves the method to be valid and therefore applied to samples collected from the West River and
its tributaries. The caffeine concentration in the samples directly relates to the sewage
contamination due to overflow of combined sewer pipelines, leaky septic tanks and other sources.
West River has maximum contamination of sewage as compared to its tributaries; this could be
due to more leakages from the nearby watershed area.
Keywords: Caffeine, Solid Phase Extraction, Gas Chromatography/Mass Spectrophotometer,
West River, Selected Ion Monitoring.
