The sensitivity, selectivity and real-time analysis offered by SIFT-MS solution provides simple, reliable and continuous analysis of trace volatile organic compounds in ambient air.


Volatile organic compounds (VOCs) are typically found in air in the part-per-trillion and part-per- billion by volume (pptv and ppbv) concentration range. Since both anthropogenic and biogenic sources of VOCs display significant time dependence, traditional GC/MS methodologies are unsuitable, due to preconcentration requirements and slow analysis times.

Alternatively, Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) detects and quantifies VOCs in real- time in air to pptv levels with no sample preparation. This application note illustrates how readily a Syft Technologies’ Voice200 SIFT-MS instrument can be deployed for a short-term campaign to provide detailed, real-time VOC analysis.

A Syft Voice200 instrument was deployed at Shu-Lin Primary School in Taoyuan County, near Taipei, Taiwan R.O.C. from 19 to 21 July 2011. The school is situated adjacent to an industrial area. Concentration data were obtained for 48 compounds, many of which had been previously identified at the site using GC/ MS. Results are shown in Figures 1 and 2 for several compounds that exhibited interesting trends, including toluene, methanol, isopropyl alcohol, acetone and N,N- dimethylformamide. Concentrations ranged from sub-ppbv to peak levels for methanol of ~250 ppbv.

Ambient Air Monitoring 1

Figure 1. Temporal concentrations of aromatic and oxygenated compounds derived from full scan SIFT-MS data.*

Ambient Air Monitoring 2

Figure 2. Comparison of the performance of two SIFT-MS reagent ions for analysis of N,N-dimethylformamide.*

* The instrument was used to perform other analyses between 11am and 12pm on 20July.

Elevated concentrations indicate periods when pollutants were released from a stack. Instantaneous variations arise from gusty wind conditions at the coastal site. The use of multiple reagent ions per compound confirms that changes are real and provides enhanced selectivity compared to other real-time techniques (reagent ions are switched in less than 10 ms in the Voice200). Figure 2 shows the close agreement obtained from independent measurements of N,N-dimethylformamide using the H3O+ and NO+ reagent ions with their m/z = 74 and 72 product ions, respectively.

The high-speed analysis provided by SIFT-MS makes it ideally suited to continuous monitoring of ambient VOCs. The Syft Voice200 SIFT-MS solution provides a robust, easily deployed and operated package for sensitive, quantitative real-time monitoring of a diverse range of VOCs and inorganic gases.

 

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