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Thomas Library

Honors Thesis Archive

Author Betty Jean Cheney
Title Single Drop Microextraction: An Educational Undergraduate Laboratory Procedure Using Caffeine and DEET
Department Chemistry
Advisor Kristin Cline
Year 2010
Honors University Honors
Full Text View Thesis (431 KB)
Abstract Single drop microextraction (SDME) is applicable for the analysis of caffeine and DEET in aqueous samples in an undergraduate laboratory. A drop of organic solvent (toluene or chloroform) is suspended in stirred aqueous solution in order to extract the desired analyte. The drop is injected into a gas chromatograph mass spectrometer in single ion monitoring (SIM) mode. The chromatograms are integrated to construct a calibration curve using the peak areas. The following variables were optimized: drop size (0.5 microliters), stirring rate (200 rotations per minute), sample volume (4 milliliters), extraction time (5 minutes), and chloroform as the organic extraction solvent. When caffeine was extracted into chloroform the percent relative standard deviation of the peak areas and detection limit were 2 to 38% and 1.1x10-3 mg/mL. The caffeine extracted into chloroform showed good linearity with a correlation coefficient of 0.995. Samples of Diet Coke, Barq's Root Beer, Xenergy energy drink, Twinings Lady Grey Tea, and Stash Vanilla Chai Decaf Tea were all prepared and analyzed for caffeine content in comparison to reported values. DEET (N,N-diethyl-3-methylbenzamide) extracted into chloroform had a percent relative standard deviation and detection limit of 2 to 64% and 6.6x10-3 mg/mL. The DEET extracted into chloroform showed good linearity as well, with a correlation coefficient of 0.960. Internal standards were not successfully applied to the extractions with either caffeine, DEET, or para-xylene. Other adaptations of SDME include the analysis of ethanol in mouthwash and phenol in Chloraseptic® spray. Overall, the procedure is easily reproduced and requires equipment and solvents found in most undergraduate laboratories. Students were able to complete the procedure with relative ease and good reproducibility.

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