Andreas Walte

Online Measurement of Polycyclic Aromatic Hydrocarbons by Fast GC/MS

Abstract A novel system, based on gas chromatography mass spectrometry has been developed for the on-line assessment of PAH at combustion processes. The analytical results are obtained on site after minutes. Because of their wide range of volatility, PAHs always occur in a gaseous fraction and a particle adsorbed fraction. A sampling technique for the particulate fraction, based on the dilution method and filter tape sampling, has been constructed. By thermodesorption, fast GC and the combination with a membrane inlet system for the MS an analysis down to the ppb level at a cycle rate of 5 minutes has been achieved. Quick GC runs are possible because of the light weight construction of the chromatographic system. This analytical system has been tested on-site at several emission sources (oil combustion plants, coke oven and diesel engines). Analytical results demonstrate the advantages of this concept. A comparison is done with results from other methods.

Measurement of Aromatic Compounds in Automobile Exhaust Gases with Membrane Inlet Mass Spectrometry Equipped with an On-Line-Probe and an Automatic Tenax-Sampler

A novel membrane inlet mass spectrometer is used to monitor organic compounds in combustion emissions. Different gas probes, which can be changed in minutes, have been developed for use in combination with the mobile mass spectrometer. With the On-Line-Probe, volatile organic compounds (BTXE) can be measured down to the ppm range with a cycle rate of one analysis per second. Time resolved measurements of aromatic compounds together with other exhaust gases can be done. By sampling with a polymer adsorbent, analysis with thermal desorption and GC/MS down to the ppb concentration range can be achieved. A six-fold Tenax-Sampler, connected to the mobile GC/MS system, is capable of taking and transferring the samples automatically. Because sampling with this device is independent from the analysis, measurements of narrow time windows in a dynamical process can be done easily. The whole analytical equipment was evaluated on-site through measurements on an engine test stand, a dynamometer and on the road during real traffic. It is shown, that time resolved quantitative measurements give information on the influence of special driving conditions (warm up, congestion) on the amount of aromatic compounds emitted by automobile exhausts.

Detector Array with Gas Chromatograph for On-Site Analyses

Toxic and environmentally threatening gaseous substances can be released on purpose or by accident e.g. during transportation or handling. In this cases fast, reliable detection, identification and quantification is needed to face the threat effectively. Therefore the handheld measurement device DACHS was developed. It combines different sensor technologies to an array to provide a quick on-site analysis for the most important industrial substances. The most sensitive sensor in the developed instrument is an ion mobility spectrometer (IMS), but the IMS cannot detect all toxic gases. Therefore additional sensors are needed. To obtain reliable identification during the presence of mixtures of different chemicals a short column gas chromatograph with enrichment unit is included. The device and the results of its evaluation are presented.