Development of a Method for Determination for Atmospheric Volatile Methylsiloxanes and Its Application to Environmental Monitoring

摘要

To determine atmospheric concentrations of cyclic and linear volatile methylsiloxanes (VMS), material blanks, sample storage conditions, and optimization of GC/MS conditions were examined. A simple air-sampling method using a solid-phase extraction (SPE) cartridge attached to a mass-flow controlled diaphragm pump was established. For GC/MS analysis, the peak shapes of VMS were improved by using a press-fit type inlet liner. This achieved high sensitivity of VMS, especially for highly volatile compounds, such as hexamethylcyclotrisiloxane (D3). To reduce instrumental and method blanks of VMS, we selected GC parts and lab materials that showed low levels of VMS in a hexane elution test. In a sample storage condition test, no significant loss of cyclic VMS was observed for up to 7-days of storage in a freezer. Using the established method, we conducted the air monitoring of VMS over one year (February 2014- February 2015) in Kazo City, Saitama Prefecture. The total of the 7VMS concentrations varied widely from 63 to 1150 ng m(-3), with a 100 % detection frequency for all VMS measured, except for octamethyltrisiloxane (L3). The mean concentrations of the two main VMS, octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5), were 123 ng m(-3) and 118 ng m(-3), respectively, which was shown to be within the range of the concentrations in urban areas from other countries. The concentrations of linear VMS were observed at two orders of magnitude lower than those of cyclic VMS. The annual profiles of VMS concentrations and D4/D5 ratios tended to shift together, suggesting that the wide variation of the VMS concentrations found in this study could be caused by daily variations of the D4 concentrations. To date, this is the first study to report on the concentration profiles of individual VMS in the atmospheric environment of Japan.