# A Simple Alternative Method for Preservation of 2-Methylisoborneol in Water Samples
## 1 Introduction  
Taste and odor (T&O) is an important issue for drinking water in many countries [1; 2; 3; 4; 5; 6; 7]. Among the many T&O compounds reported in the literature, 2-methylisoborneol (2-MIB) and trans-1,10-dimethyl-trans-9-decalo (geosmin) are the two most common chemicals detected in drinking water systems [6]. These compounds have caused customer complaints for decades [8]. Although they are of no concern to human health, they may raise customer suspicions related to water safety [9]. Therefore, detection and treatment of these compounds in drinking water are required so the water quality can be improved and the complaints of consumers can be reduced. In drinking water sources, geosmin and 2-MIB can be produced from various microorganisms, including cyanobacteria [10; 11], actinomycetes [12], fungi [13], and myxobacteria [14]. Although the contribution of actinomycetes and other microorganisms on geosmin and 2-MIB in source water cannot be neglected, cyanobacteria are generally considered as the major source of the two compounds. Many genera of cyanobacteria, including _Anabena_, _Lyngbya_, _Oscillatoria_, _Phormidium_,_Planktothricoides, Planktothrix_, and _Pseudanabena_, have been reported to be the producers of geosmin and/or 2-MIB [2; 15; 16; 17; 18; 19]. Removing the two T&O compounds from drinking water is a challenge for water authorities internationally. In particular, consumers experience the two compounds as a musty, earthy odor at levels as low as 5-10 ng L\({}^{-1}\)[20]. Therefore, the treatment methods for these compounds must be very effective [20]. Depending on the cyanobacteria strains, growth status, and environmental conditions, the odorants may either be contained within the cells (cell bound) or released into the water in a dissolved form [21]. These metabolites, particularly in their dissolved (extracellular) forms, have been shown to be somewhat unresponsive to conventional water treatment [22; 23]. Therefore, understanding the ratio of intracellular and dissolved concentrations of the odorants is also important for water utility companies. Analysis of geosmin and 2-MIB is commonly achieved by headspace solid phase microextraction (HS-SPME) coupled with gas chromatograph and mass spectrometry (GC-MS). In practical cases, water samples with geosmin and 2-MIB are taken in the field, including water sources and finished water, stored in amber glass vials with no headspace, and stored at 4 \({}^{\circ}\)C before analysis. As suggested in the APHA Method 6040 (2014), the samples should be analyzed within 14 days after the sampling. However, if the samples cannot be analyzed in 3 days, it is suggested that 10 mg L\({}^{-1}\) of mercuric chloride be added into the sample to arrest biological degradation ([PERSON] et al., 2014). Several studies have demonstrated bacterial degradation of 2-MIB even under low-temperature conditions in natural waters [24; 25; 26; 27]. A few bacterial strains capable of degrading 2-MIB in water have been isolated from water treatment plants and reservoirs [24; 26; 28]. Therefore, if no preserving agent, such as mercury chloride, is added, biodegradation is expected to occur in samples after longer storage periods, leading to underestimation of 2-MIB and geosmin concentrations in the measurement. In water treatment plants, chlorine and permanganate are commonly used for oxidation and/or disinfection. Studies [22; 23; 29; 30] have demonstrated that 2-MIB is resistant to these two chemicals [29; 30; 31; 32]. Less than 10% 2-MIB and geosmin were removed during chlorination and permanganation, at a chlorine dose = 2-10 mg Cl\({}_{2}\)/L and permanganate = 10 mg/L. Although the toxicity of the two chemicals is expected to be lower than that of mercury chloride, they are bactericidal and may inhibit the biodegradation effect of 2-MIB in water samples. Because chlorine and permanganate do not destroy the two odorants, these two oxidants may be used as alternative preservation agents for 2-MIB and geosmin in water samples.