# A Simple Alternative Method for Preservation of 2-Methylisoborneol in Water Samples
## 3 Results and Discussion
### Impact of Permanganate on 2-MIB Concentration in Natural Water  
In the permanganate preservation experiments in natural water, three sources of water with the presence of 2-MIB--water from the NH, AGD and ZW reservoirs--at two temperatures, 4 and 25 \({}^{\circ}\)C, were tested with permanganate doses at 10 mg/L, for which the results are shown in Figure 2. It is noted in the figure that the control experiments represent samples with no addition of the chemical. As expected, 2-MIB concentrations were reduced significantly, by 26.1%-55.4%, for all the three tested waters within 14 days, which was likely due to biodegradation, as discussed in the previous section. For the preservation experiments with permanganate in the natural waters, unlike the results for deionized water where there was only \(<\)10% of reduction in 2-MIB concentrations with 14 days of preservation with 10 mg/L of permanganate, a 15%-26% and 23%-50% was found for the 2-MIB for the three tested natural waters at 4 \({}^{\circ}\)C and 25 \({}^{\circ}\)C, respectively. As shown in Figure 1 and in a report from [PERSON] et al. [22], permanganate was not able to oxidize 2-MIB effectively. In addition, in the current experimental system, the loss of 2-MIB was not due to volatilization, as demonstrated in the control experiments (Figure 1). Since permanganate concentrations in the reactors were higher than 3.9 mg/L throughout the experiments (Figure 2D) and permanganate is a bactericidal [34], it is expected that biodegradation would not be an important mechanism related to concentration reduction. Permanganate is known to form manganese dioxide (MnO\({}_{2}\)) particles after oxidation [35], and therefore the adsorption of 2-MIB onto the MnO\({}_{2}\) was suspected to have caused the  
Figure 1: Changes of 2-MIB concentration in deionized water samples preserved with chlorine and permanganate at two temperatures, where initial 2-MIB concentration is (**A**) 20 mg/L and (**B**) 100 mg/L. concentration change in 2-MIB in the system. To clarify the interaction between manganese dioxide and 2-MIB, a set of adsorption experiments were conducted. The experiments were similar to those used for the oxidation experiments except that 1 mg/L MnO\({}_{2}\) and 100 ng/L 2-MIB were used, and the adsorption time was 14 days. Figure 3 illustrates the concentration changes in 2-MIB in the adsorption experiments. In the figure, the filtrate represents the samples filtered through a 0.3 \(\upmu\)m-fiberglass filter (Advantec GF-75, Tokyo, Japan) before analysis, while the total represents the samples analyzed without filtration. The figure demonstrates that 2-MIB was reduced by 55.8% and 67.5% after reaction for 14 days for the samples with and without filtration, respectively. The results suggest that the MnO\({}_{2}\) particles, both larger and smaller than 0.3 \(\upmu\)m, were able to adsorb 2-MIB and cause a reduction in 2-MIB concentration. In the preservation experiments in natural water, 3.59-5.88 mg/L of permanganate were transformed into MnO\({}_{2}\) in natural water (Figure 2D), approximately equal to 1.2-1.9 mg/L if based on stoichiometric calculation. Although the initial 2-MIB concentration between the permanganate preservation experiments in natural water (Figure 2) and the MnO\({}_{2}\) adsorption experiments (Figure 3) were different, both experiments proved that removal of 2-MIB could be attributed to adsorption onto MnO\({}_{2}\) in the two systems. For the permanganate preservation experiments in deionized water (Figure 1), less than 0.2 mg/L of MnO\({}_{2}\) was expected to form, leading to lower adsorption of 2-MIB on MnO\({}_{2}\). Therefore, the concentration reduction was not observed for 2-MIB. In natural water systems, many components, such as natural organic matters, algae metabolites, and reduced substance [36; 37], may react with permanganate and form MnO\({}_{2}\), causing adsorption of 2-MIB in the water.