1998 Progress Report: Techniques for Standardization, Validation, and Measurement of Targeted Trace Gases Which Participate in Tropospheric Ozone FormationEPA Grant Number: R825261
Title: Techniques for Standardization, Validation, and Measurement of Targeted Trace Gases Which Participate in Tropospheric Ozone Formation
Investigators: Apel, Eric C. , Fried, Alan , Gilpin, Tim
Current Investigators: Apel, Eric C. , Fried, Alan , Gilpin, Tim , Riemer, Dan
Institution: National Center for Atmospheric Research
EPA Project Officer: Shapiro, Paul
Project Period: January 1, 1997 through December 31, 1999
Project Period Covered by this Report: January 1, 1998 through December 31, 1999
Project Amount: $472,250
RFA: Air Quality (1996) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:The research objectives covers three distinct areas: (1) the development of necessary standards for target oxygenated volatile organic compounds (OVOCs); (2) the development of accurate analytical methods, including a formaldehyde method, to verify the standards and to lay the groundwork for reliable ambient measurements; and (3) development of a calibration facility whereby university researchers, including PAMS personnel (cartridges), may come to calibrate and test their instruments under simulated ambient conditions.
Progress Summary:Progress has been made towards accomplishing the objectives in the three areas described above. We have spent most of this year developing accurate analytical methods. We have further developed our standard preparation techniques this year and have made several OVOC standards in high pressure aluminum cylinders by the following methods. Testing on them has begun.
NCAR High Pressure Method 1 Standard Preparation. Pure starting materials (purity verification with GC/MS analysis) were transferred into a known volume via a high vacuum line. Upon introduction of the compounds of interest, the increased pressure of the known volume was measured with a calibrated pressure transducer (MKS-Baratron), giving a quantitative amount. The pure starting material within the known volume was then transferred to a larger volume and diluted with ultra high purity zero air or N2 that has been scrubbed and analyzed to insure purity (purity analysis by either: GC/FID, GC/ECD, GC/MS, or by any number of assorted techniques available at NCAR depending on the compound). This sequence was repeated with a series of volumes until the desired concentration was obtained.
NCAR High Pressure Method 2 Standard Preparation. This method used a heated injector that allows introduction of known amounts of the compound(s) of interest directly into a treated, evacuated, previously weighed cylinder. The known amount is introduced into a calibrated flowing stream of diluent gas. The combination of the flowing stream of gas and the heated injector insure that all of the starting material is swept into the previously weighed cylinder. The cylinder was then pressurized to the desired amount (calibrated high-pressure transducer) and allowed to equilibrate over several days. The cylinder is then re-weighed on the same high accuracy (0.1 g) balance. This method is used to prepare low ppmv (and high ppbv) standards which are normally used with a calibrated dynamic dilution device. There is merit in preparing ppm standards as the stability of the compounds at these levels in properly treated cylinders is good.
A manually operated GC/FID method using an HP-624 column was developed and is
currently being used to monitor concentrations. This system was designed to be
as simple and accurate as possible. This system is shown below in Figure 1.
Figure 1. Manually operated preconcentrator GC/FID system used to measure OVOCs.
A new-design auto GC/FID/MS has also been developed and has come on line (Figure 2). A modular OVOC permeation tube system has been built and has come on line. A formaldehyde system based on the Hantzsch reaction has been developed and is currently being refined and tested. Standards have been made and testing has begun.
Figure 2. Auto preconcentrator GC/MS for measuring OVOCs.
Future Activities:We will continue to progress as specified in our proposal. We will continue to develop the multi-technique approach to generate high quality OVOC standards and validate them with state-of-the-art techniques.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 9 publications||4 publications in selected types||All 4 journal articles|
||Apel EC, Calvert JG, Greenberg JP, Riemer D, Zika R, Kleindienst TE, Lonneman WA, Fung K, Fujita E. Generation and validation of oxygenated volatile organic carbon standards for the 1995 Southern Oxidants Study Nashville Intensive. Journal of Geophysical Research-Atmospheres 1998;103(D17):22281-22294.||
||Apel EC, Calvert JG, Riemer D, Pos W, Zika R, Kleindienst TE, Lonneman WA, Fung K, Fujita E, Shepson PB, Starn TK, Roberts PT. Measurements comparison of oxygenated volatile organic compounds at a rural site during the 1995 SOS Nashville Intensive. Journal of Geophysical Research-Atmospheres 1998;103(D17):22295-22316.||