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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.

A new multicomponent exhaust gas analyzer has been applied to investigate the time-resolved concentrations of the aromatic hydrocarbon exhaust components benzene, toluene, xylene, trimethyl benzene under dynamic engine operation, such as sudden change of speed and load, misfiring and switching off the fuel mixture control. The analyzer consisting of a compact laser mass spectrometer is capable of measuring the concentrations of the individual aromatic hydrocarbon compounds simultaneously with 1 ppm sensitivity at a sampling rate of 50 Hz corresponding to a sampling period of 20 ms. High concentration peaks are observed for these substances at instationary motor operation. However, whereas the real-time concentrations of toluene, xylene, and trimethyl benzene show equal dependence on motor speed and load a different behavior has been observed for benzene even during the emission phase of single combustion cycles.

Given the legal requirements for quality assurance of passenger car exhaust emissions worldwide we define our quality assurance system and present the emission laboratories of the Mercedes-Benz assembly plants Sindelfingen and Bremen. We developed a hierarchically structured, multi-level computer system, which enables us to automize emission test procedures, calibration, maintenance of measurement systems and documentation of exhaust data. Test cell computers coordinate the different components of the test cells and perform maintenance and calibration of measurement devices, thus guaranteeing a high measurement quality with reasonable economy. The coordinating level computer, the emission host system (EHS), processes test parameters, controls and supervises the test sequences and evaluates the test results on a statistical basis.