Abstract:

The odorous compounds of 2-methylisoborneol (2-MIB) and geosmin (GSM) heavily produced and released in water source are one of the most important factors leading to off-flavor emergencies and resident water consumption panic in drinking water. A headspace solid phase micro-extraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) method was established for the simultaneous determination of these two trace earthy and musty compounds in reservoir water, reservoir soil and tap water. The conditions of HS-SPME, such as salt amount, extraction time and extraction temperature, were optimized based on orthogonal analysis. The qualitative and quantitative analyses of 2-MIB and GSM were carried out in the electron impact (EI)-selective ion scanning mode. The results showed that the linear relationship between peak area and concentration of 2-MIB and GSM was good enough (r²≥0.998) from 5 to 1000 ng/L, the limits of detection were 0.72 ng/L for 2-MIB, 0.34 ng/L for GSM and the limits of quantification were 2.40 ng/L for 2-MIB, 1.13 ng/L for GSM. When the target samples spiked in the range of 10-600 ng/L, the average recoveries of the target compounds were 93.6%-107.7% (RSD≤6.1%, n=6). Based on the above method, the target compounds in reservoir water, reservoir soil and tap water in a certain region of Liaoning Province were analyzed. The results showed that the two target odors in reservoir water were 3.0-3.6 ng/L. As for the extract of the soil around the reservoir, 2-MIB was 8.1 ng/L and GSM was 17.8 ng/L. The odorous substances were not detected in the tap water. This method is simple, accurate, reliable, highly sensitive and no need of organic solvents. And it is suitable for the detection of 2-MIB and GSM in drinking water.

Key words: 2-methylisoborneol (2-MIB), drinking water, gas chromatography-mass spectrometry (GC-MS), geosmin (GSM), headspace solid phase micro-extraction (HS-SPME), orthogonal analysis