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The ozone forming potential (OFP) and specific reactivity (SR) of tailpipe exhaust are among the regulated factors that determine the environmental impact of a motor vehicle. OFP and SR measurements require a lengthy determination of about 160 non-methane hydrocarbon species. A rapid gas chromatography (GC) instrument has been constructed to separate both the light (C2 - C4) and the midrange (C5 - C12) hydrocarbons in less than 10 minutes. The limit of detection was about 0.002 parts per million carbon (ppmC). Twelve exhaust samples from two vehicles were analyzed to compare the rapid GC method with the standard GC method, which required 40-minute analyses on two different instruments. Speciation and reactivity data from the two methods were comparable. The increased sample throughput of rapid GC promises to improve OFP and SR measurements, particularly when good statistical data are necessary to insure accurate, precise results for low emission vehicles

Analytical procedures for the speciation of hydrocarbons and oxygenates (ethers, aldehydes, ketones and alcohols) in vehicle evaporative and tailpipe exhaust emissions have been improved for Phase II studies of the Auto/Oil Air Quality Improvement Research Program (AQIRP). One gas chromatograph (GC) was used for measurement of C1-C4 species and a second GC for C4-C12 species. Detection limits for this technique are 0.005 ppm C or 0.1 mg/mile exhaust emission level at a chromatographic signal-to-noise ratio of 3/1, a ten-fold improvement over the Phase I technique. The Phase I library was modified to include additional species for a total of 154 species. A 23-component gas standard was used to establish a calibration scale for automated computer identification of species. This method identifies 95±3% of the total hydrocarbon mass measured by GC for a typical exhaust sample. Solid adsorbent cartridges or impingers were used to collect aldehydes and ketones.

An analytical method for the determination of hydrocarbon and ether emissions from gasoline-, methanol-, and flexible-fueled vehicles is described. This method was used in Phase I of the Auto/Oil Air Quality Improvement Research Program to provide emissions data for various vehicles using individual reformulated gasolines and alternate fuels. These data would then be used for air modeling studies. Emission samples for tailpipe, evaporative, and running loss were collected in Tedlar bags. Gas chromatographic analysis of the emissions samples included 140 components (hydrocarbons, ethers, alcohols and aldehydes) between C1 and C12 in a single analysis of 54-minutes duration. Standardization, quality control procedures, and inter-laboratory comparisons developed and completed as part of this program are also described.