| dc.description.abstract | With the rapid growth in economy and industrialization, air pollutants are being constantly released into the atmosphere. To understand the role of volatile organic compounds (VOCs) as precursors to form ozone in the presence of NOx, the Environmental Protection Administration (EPA) of Taiwan has established Photochemical Assessment Monitoring Stations (PAMS). These stations utilize Gas Chromatography/Flame Ionization Detector (GC/FID) and the heart-cut technology to form an online analytical system. The PAMS system can measure 54 VOCs on the per hourly basis, but only covers few hazardous air pollutants (HAPs) species. However, if mass spectrometry (MS) is used for detection in a similar system, significantly more HAPs can be measured.
In previous studies, our self-developed analytical system was used for online monitoring of HAPs both in a trailer owned by the Taichung City Environmental Protection Bureau and in a fixed station of Formosa Plastics Corporation. The former employed a single column with GC/MS to analyze HAPs, while the latter utilized a single column but split the flow in parallel to MS and FID with GC/MS/FID to monitor 12 target compounds. Since each chromatographic column is usually only suitable for separation within a specific polarity range, therefore it is difficult to separate highly complex samples using a single column, leading to co-elution in certain portions of the chromatogram and thus subsequent difficulties in quantification.
This study developed a unique analysis technique combining heart-cut and a dual-column setup to improve upon these limitations. Using DB-1 and PLOT columns and a Deans switch for heart cutting, the C2-C12 compounds are divided into light and heavy fractions entering PLOT and DB-1, respectively. Before detection, the flows from the two columns are then merged and split again to FID and MS in parallel. The FID is responsible for quantification, whereas MS assists in qualitative analysis, enabling future monitoring stations to be equipped with sufficient capabilities for qualitative and quantitative analysis of VOCs, particularly HAPs.
This research utilized a mobile trailer to house a self-developed GC/MS system. Unlike fixed stations, the mobile trailer provided mission-oriented mobility. However, the major drawback was the instability of electricity due to the often unsatisfactory local infrastructure. Nonetheless, the online water thermal desorption (DW-TD) GC/MS/FID system developed in the laboratory was able to be successfully validated. Moreover, the self-developed DW-TD can be coupled with different brands of GCs, eliminating the constraints of being bound to specifications by foreign makers. The heart-cut technology described above is suitable for practical field tasks in industrial areas to closely monitor toxic VOCs. | en_US |