Distribution of Caffeine between Selected Water-Organic Solvent Media

Caffeine has been recognized as a pollutant to environmental water worldwide, which may highly be due to its high consumption rate. Furthermore, caffeine has been used as a chemical tracer for the impairment of surface water and potable water with untreated domestic wastewater. The major objective of this study was to determine, which organic solvents are suitable for the liquid-liquid extraction (LLE) of caffeine from pure water by comparing their distribution coefficient (Kd). Caffeine was measured via gas chromatography-mass spectroscopy (GC-MS) without the use of any pre-concentration or reconstitution step. The method is based on direct injection after LLE and standard addition prior to analysis. Chloroform and dichloromethane were found to be primer solvents for LLE of caffeine with Kd values ranging from 9.2 to 9.9. However, chloroform may be considered more suitable for LLE as dichloromethane is more temperature labile than chloroform. No significant differences were found with the influence of temperature (20°C to 30°C) and pH (approximately 2 to 12) using chloroform as an extraction solvent. Moreover, salinity (0.01 M) had a positive effect on the LLE of caffeine with chloroform. This suits the tropical Caribbean environment of the university as caffeine measurements in environmental water should be insignificantly affected by the aforementioned abiotic factors. The non-polar solvents (benzene, diethyl ether, ethyl acetate and hexane) showed very poor extraction of caffeine from water achieving Kd values u003c 1.0.