Effect of pH on the Analysis of 2-MIB and Geosmin in Water |
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Authors: | Wen-Hsing Hsieh Wei-Nung Hung Gen-Shuh Wang Shu-Ting Hsieh Tsair-Fuh Lin |
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Institution: | (1) Department of Environmental Engineering, National Cheng Kung University, Tainan, 70101, Taiwan;(2) Sustainable Environment Research Center, National Cheng Kung University, Tainan, 70955, Taiwan;(3) Institute of Environmental Health, National Taiwan University, Taipei, 10055, Taiwan; |
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Abstract: | 2-Methylisoborneol (2-MIB) and trans-1,10-dimethyl-trans-9-decalol (geosmin) are two commonly observed taste and odor compounds present in drinking water sources. The effects of
pH on the analysis of the two chemicals are investigated using a gas chromatograph and mass spectrometric detector (GC/MSD)
coupled with three pre-concentration methods, namely solid-phase micro-extraction (SPME), purge-and-trap concentration (PTC),
and liquid–liquid extraction (LLE). At neutral and alkaline pH conditions, the concentrations detected for both compounds
remain constant. However, a substantial reduction of concentration for both chemicals is observed when the water solution
pH is less than 5. Under acidic conditions (pH ≅ 2.5), the 2-MIB concentrations detected by GC/MSD coupled with SPME, PTC,
and LLE are 87%, 16%, and 37% lower than those measured at pH 6–7, respectively. For geosmin, a decrease in concentration
is only observed when using GC/MSD-SPME, presumably due to the higher extraction temperature compared to the other two techniques.
The pH-dependent behavior was attributed to dehydration of the tertiary alcohols of 2-MIB and geosmin under acidic conditions.
The dehydration for 2-MIB and geosmin is reversible, and the analysis can be mitigated by adjusting the water solution pH
back to a neutral condition. |
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