Determination of 2-Methylisoborneol and Geosminin Water by Using Stir Bar Sorptive Extraction-Thermal Desorption Coupled with GC-MS

In water system, odorous compounds are often associated with the metabolites of microorganisms as fungi and blue-green algae, and the related compounds have been commonly found in lakes and reservoirs. Among those compounds, geosmin (GSM) and 2-methylisoborneol (2-MIB) have been treated as main odor compounds, which cause the off-flavor issues in natural sources such as freshwater, water reservoirs, marine water ecosystems and even in drinking water. Since of the strong smell of GSM and 2-MIB with earthy flavor and odor, they can be simply detected by human nose. Although those compounds are harmless to human health at certain level, high accumulation in natural water and drinking water led to an undesirable odor. Thus, the detection of the presence of those off-flavor compounds is first step to address above problem. To analysis the undesirable odorous compounds in water and aquaculture products, a concise and sensitive method has been developed by using stir bar sorptive extraction-thermal desorption coupled with gas chromatography-mass spectrometry (SBSE-TD-GC-MS) in the study. SBSE-TD-GC-MS has been optimized and validated through analyzing 2-MIB and GSM in aquatic samples. The calibration curves of 2-MIB and GSM were linear in the range of 0.5-100 ng/L (r(2) > 0.995, RSDs < 3.5%). The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) of 2-MIB and GSM were both similar to 0.2 and 0.5 ng/L, respectively. The recoveries of 2-MIB and GSM were 86-113% with good precision (RSDs < 8%) by spike in 2.5 and 25 ng/L standard compounds. This method was successfully applied to monitor and determinate the amount of 2-MIB and GSM in four types of water samples. Thus, SBSE-TD-GC-MS, a developed technique with high sensitivity and good recoveries, can be applied to detect odorous compounds at very low concentration, by using significantly smaller amounts of water samples, without any pre-concentration.