# Comparison of Water Pretreatment Devices for the Measurement of Polar Odorous Compounds
## 4 Conclusions  
A comparison between a Desolvator-K and two commercial coolers as water pretreatment devices was carried out in this study. The target compounds were MEK, i-BuAl, MIBK, and BuAc, which were the polar odorous compounds of VOCs in air, and styrene was used as a simple comparison compound. The water vapor removal efficiency, recovery rate, and reproducibility were evaluated for each device. Water vapor removal was confirmed as the basic performance of the water pretreatment device. The manufactured Desolvator-K, which showed the highest water vapor removal (85.3-91.6%), could reduce sample RH to less than 10% after removing the water vapor. However, the samples of Cooler-G (53.9-67.2%) and Cooler-K (34.2-62.1%) were found to be around 30% RH. Therefore, it was observed that the Desolvator-K is more suitable as a water pretreatment device than the coolers because they could be damaging to the instrument or disturb analyte detection if unremoved water vapor is introduced to the analyzer. In the recovery test of the odorous compounds, the manufactured Desolvator-K showed the highest recovery rates (96.6-103%) and reproducibility (less than 5.94% RSD) for each target compound under all conditions. The Cooler-G, on the other hand, showed recovery rates of 81-101% and unstable reproducibility of less than 31.2% for all target compounds under all conditions. The Cooler-K showed recovery rates of 88.6-100% for all target compounds under all conditions and somewhat unstable reproducibility of less than 8.14%. Thus, the coolers showed unstable recovery rates and reproducibility depending on the compound. It was also considered that it was not appropriate to use an unreliable water pretreatment device when analyzing a trace amount of a compound and requiring low humidity because a cooler has a relatively low water vapor removal. On the other hand, the Desolvator-K also denoted higher water vapor removal and higher recovery than the coolers. Therefore, it could be considered that the Desolvator-K can be used as a water pretreatment device for the odorous compounds used in this study. Therefore, Desolvator-K has higher water vapor removal efficiency and higher analyte recovery rate than other coolers. In terms of durability, both water pretreatment devices have a similar durability (about 3-5 years). Instead, the Desolvator-K might have a higher initial cost than other devices, and might consume more energy depending on the use environment. Nonetheless, a suitable water pretreatment device is pivotal key for accurate and reliable measurements for the characteristics of each analyte. Particularly, when polar and water soluble compounds with trace amounts are measured, the selection of a water pretreatment device capable of selectively removing water vapor without any interference on the analyte is the most important issue. As a result of this study, the Desolvator-K could be used as a water pretreatment device for the MEK, i-BuAl, MIBK, BuAc, and styrene compounds. The comparison with coolers was only conducted in this study. However, the Nafion(r) dryer is widely used all over the world. Consequently, a comparison between the Desolvator-K and the Nafion(r) dryer should be implemented in future work. Conceptualization, [PERSON]-Y.L. and [PERSON]; methodology, [PERSON]-Y.L., [PERSON]-[PERSON], and [PERSON]-[PERSON]; validation, [PERSON]-Y.L. ; formal analysis, [PERSON]-Y.L., [PERSON]-V.D., [PERSON], [PERSON], and [PERSON]-Y.P. ; investigation, [PERSON]-Y.L. and [PERSON]-[PERSON]; resources, [PERSON]-Y.L. and [PERSON]; data curation, [PERSON]-[PERSON] and [PERSON]-[PERSON]; writing--original-draft preparation, [PERSON]-Y.L. and [PERSON]-[PERSON]; writing--review and editing, [PERSON]-Y.L., [PERSON]-[PERSON], and [PERSON]-[PERSON]; visualization, [PERSON]-[PERSON]; supervision, [PERSON]-[PERSON] and [PERSON]-V.D. ; project administration, [PERSON]-Y.L. and [PERSON]-[PERSON].