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Development of an LC-APCI-MS Method for Determining Off-Flavor Compounds and its Application Towards Marine Recirculating Aquaculture System Monitoring and Evaluation of Aeration as a Depuration Approach

Published

Author(s)

Mary Bedner, Keiko Saito

Abstract

The off-flavor compounds geosmin and 2-methylisoborneol (2-MIB) are well-known to impact the quality of farmed freshwater fish species, but little is known about off-flavors in marine aquaculture. To begin addressing this knowledge gap, a method for the direct aqueous determination of geosmin and 2-MIB using liquid chromatography (LC) with atmospheric pressure chemical ionization (APCI) mass spectrometric (MS) detection was developed. While 2-MIB was readily detected using LC-APCI-MS, geosmin exhibited on-column degradation that was independent of column chemistry and could not be eliminated. Optimized conditions were identified that balanced the separation and ionization efficiency of 2-MIB and geosmin while minimizing geosmin degradation. The method was used to evaluate the volatilization rates of geosmin and 2-MIB during aeration under laboratory conditions in both salt water and pure water to simulate marine and fresh water aquaculture, respectively. The volatilization rates of both compounds were 30 % faster in salt water than in fresh water with or without aeration, but aeration was found to enhance the rate by a factor of 2.5 in both water types. These results indicate aeration is worth further evaluation for off-flavor removal, particularly in marine systems. The LC-APCI-MS method was combined with stir bar sorptive extraction (SBSE) to determine geosmin and 2-MIB at the low part-per-trillion (ppt) levels required for aquaculture monitoring, and the resulting limits of detection (LOD) were 70 ppt and 6 ppt, respectively. The on-column losses resulted in a higher LOD for geosmin. SBSE using both grab water samples and an in-situ diving unit were used to evaluate geosmin and 2-MIB levels in the culture water of two separate marine recirculating aquaculture systems (RAS) that were supporting the growth of European sea bass but had differing levels of water treatment. 2-MIB was readily detected using both SBSE approaches in the RAS with less sophisticated treatm
Citation
Journal of Chromatography A
Volume
1609

Keywords

Geosmin, 2-methylisoborneol, marine aquaculture, off-flavor, recirculating aquaculture systems, aeration, liquid chromatography, mass spectrometry, stir bar sorptive extraction, bronzini
Created January 4, 2020, Updated March 10, 2020