Extraction and Detection of Geosmin and 2-Methylisoborneol in Water and Fish using High-Capacity Sorptive Extraction Probes and GC-MS.

Geosmin and 2-methylisoborneol are volatile organic compounds of microbial origin that frequently occur in recirculating aquaculture systems and confer unpleasant odors and flavors to fish therein, even at extremely low concentrations. Existing analytical methods for these compounds in fish struggle to achieve enough sample throughput and are oftentimes not automated, requiring extensive hands-on preparation. We have developed methods for analyzing geosmin and 2-methylisoborneol from water and fish tissues, respectively, using a metal probe bearing a high-capacity sorptive extraction phase. A robust and quantitative detection was achieved from both water and fish tissues, with minimum detection limits of 1.2 ng/L for geosmin and 1.1 ng/L for 2-methylisoborneol from water and 18.1 ng/kg and 13.6 ng/kg, respectively, from fish tissue. These concentrations were well below human detection thresholds. Hence, we concluded that these methods could detect geosmin and 2-methylisoborneol before they became perceptible to humans. In contrast to other high-capacity sorptive extraction techniques, such as stir-bar sorptive extraction, this technique is fully automatable, dramatically improving throughput and precluding manual handling errors, while the durable design of the probe precludes breakage, such as is common with solid phase microextraction (SPME) fiber. This method is suitable for odorant monitoring in all water quality settings, as well as for the detection of off-flavor compounds in solid and semi-solid matrices.