Research Program Area: Atmospheric Processes
Recent concern regarding the mutagenic and carcinogenic properties of ethylene oxide has created the need for the development of sensitive analytical methods capable of determining the presence of ethylene oxide in air samples at levels ranging from 5 pptv in ambient background samples to near percentage levels in process vent streams. Accordingly, the California State Air Resources Board (CARB) selected Coast-to-Coast Analytical Services, Inc. (CCAS) to develop analytical methods which would be capable of spanning these extremely broad concentration ranges.
This research verified that samples could be collected cryogenically using U-Tubes or using SUMMA electropolished stainless steel canisters. In both cases, samples suspected of containing acid mists could safely be passed through a sodium bicarbonate cartridge during collection in order to prevent post-collection breakdown. Samples collected by the U-Tube method may be held indefinately while those collected in canisters require a more immediate analysis, particularly if concentrations are expected to be below 1 ppmv. Due to differences in the ways in which samples are transferred to the instrumentation, lower detection limits are provided if samples are collected by the U-Tube method.
The methods listed below were developed and found to be effective. In the case of the vent stream method, NIOSH had already published the range and detection limit data which made it unnecessary for CCAS to independently develop these data. Except for the NIOSH method, the detection limits presented below are for U-Tube sample collection.
1. Ion Trap GC/MS - This method was found to be the most sensitive with a detection limit of 1 pptv.
2. Quadrupole GC/MS with Selective Ion Monitoring - This method was found to be almost as sensitive with a detection limit of 10 pptv.
3. Gas Chromatography with Photoionization Detection - The detection limit afforded by this method is dependent upon the energy of the light source. With a 10.6 ev lamp, the detection limit was 10 pptv. With a 10.0 ev lamp, the detection limit was 10 ppbv.
4. Quadrouple GC/MS with Full Scan Monitoring - This method was found to provide a detection limit of 0.1 ppbv.
5. Portable Gas Chromatograph with Photoionization Detection - Presumably the detection limit would also depend upon the energy of the lamp. Since sample preconcentration is impractical in the field, the detection limits developed by NIOSH are only 1 ppbv.
Since ambient samples could be collected in areas accessible to the general public, several hundred such samples were collected. In most cases the U-Tube method was employed. Some key results:
1. Samples collected at remote coastal locations indicated that the global tropospheric background in the Northern Hemisphere is between 15 and 25 pptv.
2. Samples collected away from known sources in several urban California locations showed levels ranging from the global background to an order of magnitude higher.
3. Samples collected near suspected sources in several urban California locations showed levels ranging from the global background to more than one ppmv.
4. Samples collected from one process stream before and after the control devices exhibited greater variability than expected with levels ranging from three ppbv to nearly 0.2 percent.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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