GC-MS/MS analysis of geosmin and 2-methylisoborneol in water

Geosmin and 2-methylisoborneol (MIB) are odorous metabolites that cause muddy and earthy taste and odor problems worldwide in drinking water supplies and fisheries. They were first identified in the early 1960s. Geosmin and 2-MIB are tertiary alcohols, each of which exists as (+) and (−) enantiomers. Odor outbreaks are caused by biological production of the naturally occurring (−) enantiomers which are some 10 times more potent than the (+) molecules. Geosmin and MIB are produced by a variety of distantly related bacteria including actinobacteria, cyanobacteria, and proteobacteria. Cyanobacteria are the major producers of geosmin and MIB in aquatic environments, while actinobacteria are the main producers of these metabolites in soil. Geosmin and MIB are detectable at very low concentrations due to the extremely low odor threshold (<10 ngl−1) of humans. 

Instrumental: Gas chromatograph Trace 1300 coupled to triple-quadrupole mass spectrometer TSQ 9000 (Thermo Scientific). VOCs in water were sampled using TriPlus RSH autosampler equipped with SPME and SPME cleaning station options. The compounds were separated on DB-35MS capillary column (25 m, 0.2 mm, 0.33 µm, Agilent) using hydrogen as a carrier gas. Nitrogen (>99.999) was used for cleaning SPME fiber before sampling and after injection and as a collision gas. The acquisition was carried out in positive EI MRM mode. The ion volume optimized for hydrogen was used for the analysis. The acquisition was controlled and data was analyzed using Xcalibur and TraceFinder software respectively.