United States Environmental Protection Agency Environmental Monitoring Systems Laboratory Research Triangle Park NC 27711 Research and Development EPA-600/S4-82-064 Jan. 1983 Project Summary Stability of Organic Audit Materials and Results of Source Test Analysis Audits R. K. M. Jayanty, W. F. Gutknecht, C. E. Decker, J. E. Knoll, and D. J. von Lehmden A repository of 40 gaseous compounds including hydrocarbon, halocarbon, and sulfur species has been established under contract with the U.S. Environmental Protection Agency (USEPA). The main objectives of this on-going project are (1) to provide gas mixtures to EPA, state/ local agencies, or their contractors, as performance audits to assess the accuracy of source emission measurements in certain organic chemical manufacturing industries, (2) to corroborate the vendor's certified analysis of the gas mixtures by in-house analysis, (3) to determine the stability of the gas mixtures with time by in-house analysis, and (4) to explore the feasibility of new audit materials as requested by EPA. Thus far, 18 compounds have been used to conduct 86 different audits. The results of these audits and a description of the experimental procedures used for analyses and available stability data are presented in the status report. Seventy percent of the audit results are within 10 percent of the expected values. Compound stabilities have been determine through multiple analyses of the cylinders containing them. Stability values for all compounds are expressed as percent change per month. Calculated changes are typically found to be a few tenths of one percent per month, though many of these changes may not be signifi- cantly different from zero. This Project Summary was devel- oped by EPA's Environmental Monitoring Systems Laboratory, Research Triangle Park, NC, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report ordering information at back). Introduction Accurate measurement of hydro- carbons, halocarbons, and sulfur- containing compounds in ambient and source samples is essential to any environmental monitoring program. The potential for achieving acceptable accuracy is enhanced by the availability of reliable standards which can be used to check or validate the measurement process. The Research Triangle Institute (RTI) under contract to the Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency (USEPA), has responded to this need by developing an extensive repository of standard i gaseous compounds. These standards are to be used in performance audits as designated by the EPA Project Officer. These performance audits are to assess the accuracy of source emission measurements in certain organic manufacturing industries. The RTI repository currently contains 40 different compounds based on anticipated needs of EPA. Table 1 lists the compounds, the . concentration ranges of each compound, and the ------- Table 1. Audit Materials Currently Held in the Repository Low Concentration Range High Concentration Range Compound No. of Cylinders Concentration Range (ppm) No. of Cylinders Concentration Range (ppm) Benzene 14 Ethylene 4 Propylene 4 Methane/Ethane Propane 4 Toluene 2 Hydrogen Sulfide 4 Meta-Xylene 2 Methyl Acetate 2 Chloroform 2 Carbonyl Sulfide 2 Methyl Mercaptan 4 Hexane 2 1,2-Dichloroethane 4 Cyclohexane Methyl Ethyl Ketone 1 Methanol 1 1.2-Dichloropropane 2 Trichloroethylene 2 1,1 -Dichloroethylene 2 1,2-Dibromoethylene 2 Perchloroethylene 2 Vinyl Chloride 9 1,3-Butadiene 1 Acrylonitrile 2 Aniline 1 Methyl Isobutyl Ketone 1 Cyclohexanone 2 Para-dichlorobenzene 2 Ethylamine 2 Formaldehyde Methylene Chloride 1 Carbon Tetrachloride 1 Freon 113 1 Methyl Chloroform 1 Ethylene Oxide 1 Propylene Oxide 1 Allyl Chloride 1 Acrolein 1 Chlorobenzene 1 Carbondisulfide 1 8- 13 5-20 5-20 17 4 6 4 4 60 300 3000 300 WOO 200 300 300 300 300 300 300 100 -400 - 700 - 20.000 - 700 - 6000(MJ, - 700(E) - 700 -700 -700 -700 •700 -700 -300 number of cylinders of each compound. Additional compounds are obtained as needed. The gaseous compounds are acquired from commercial suppliers in compressed gas cylinders; these same cylinders, along with an appropriate delivery system, are used directly as sources of the standard gas during performance audits. The compressed gas cylinder is especially suitable as an audit material because of its simplicity, portability, low cost, flexibility in analyte delivery over a broad concentration 5-20 4 5-20 2 5-20 2 5-20 2 5-20 2 5-20 2 5-20 2 3-10 - 20-80 2 1000 • 3000 5-20 4 100-600 / 700 50 - 50 - 5-20 2 300 - 700 5-20 2 100-600 5-20 2 100-600 5-20 2 100- 600 5-20 2 300 - 700 5-30 - 25 - 5-20 2 300-700 10 - 10 1 50 - 100 5-20 . 10-40 - 10 - 60 - 10 - 10 - 10 - 10 - 10 - 5-20 1 75 - 200 5-20 / 75-200 5-20 1 75-200 5-20 - 5-20 1 75-200 range, reliability, and ruggedness for interstate shipping. The accuracy of the supplier-reported levels of these compounds are verified through measurement using National Bureau of Standards - Standard Reference Materials (NBS-SRM's), commercial permeation tubes, and/or reagent grade pure liquids as standards. The permeation rate of the commercially available tubes are verified by RTI before use. The accuracy of the "known" cylinder concentrations and the stability of the compounds in the cylinders are important. Along with acquisition of new compounds and verification of their concentrations, an extensive stability study is performed. This study involves periodic analyses of the contents of each of the cylinders in the repository. Procedure Once a compound is chosen, a commercial supplier is contacted to determine if a cylinder containing that compound can be prepared. If so, the manufacturer prepares the cylinder gases and determines the concentra- tion of the analyte in the cylinder. The cylinder is sent to RTI where its contents are analyzed within seven days of its arrival. If the RTI value varies from the manufacturer's value by more than 10 percent, an analysis is performed by a third party. The cylinder contents are then analyzed one month after acquisition, two months after acquisition, and one year after acqui- sition. The cylinder contents are also analyzed before a cylinder is sent out for an audit. This preaudit analysis may substitute for the annual analysis if it occurs within a month of the normal analysis due date. All analyses are carried out using gas chromatography. The column and detector are chosen so as to be optimum for the compound being measured. Three types of standards are used to generate gas concentrations for calibration of the GC for the measure- ment of audit materials. National Bureau of Standards - Standard Reference Materials (NBS-SRM) methane and propane are used as standards for the measurement of methane and propane audit materials. These same gases are used to calibrate the chromatographic system for measurement of ethylene and propylene, assuming the FID response per carbon is constant for compound to compound. In a few others (e.g., vinyl chloride, ethylene oxide) gaseous standards are generated using permeation tubes. The standards for most of the other audit materials are prepared using pure liquids which are volatized in a clean glass bulb. Audit requests are directed to RTI through the EPA Project Officer. The cylinder and a regulator are then shipped by a freight carrier to the laboratory being audited. A letter is also included with the cylinders which provides general instructions for ------- performance of the audit. The audit concentrations are provided to the requesting agency audit coordinator. After the laboratory being audited has analyzed the contents of the cylinder, the audit coordinator reports the value(s) to RTI, which in turn reports both the measured and accepted values to the Project Officer. The laboratory being audited then is responsible for shipping the cylinder and regulator back to RTI. Results and Discussion To date, 86 individual audits have been initiated, and 83 are complete. The results obtained for a few typical performance audits are shown in Table 2 and the rest are given in the full report. Generally, the results of the audits show close agreement (±.10%) with the actual cylinder concentrations measured prior to shipment. Most of the cylinders in the repository are analyzed at least four times to determine the stability of these compounds; some are analyzed as many as eight times. An estimate of stability has been made for each cylinder that Table 2. Typical Audit Results has been analyzed at least three times. This estimate is a calculation of percent change in concentration per month over the period that RTI has performed analyses of the cylinder contents. The calculation involves a linear regression analysis of the concentration of the analyte versus time in days. The slope and intercept determined by this regression analysis are then used to calculate percent change per month by the relationship: slope % Change/Month = y intercept 100x30 Examples of stability data are shown in Table 3. Changes are noted for each compound, although these changes may not be significantly different from zero. As the number of analyses per cylinder increases, additional statistical analyses will be performed. Conclusions Cylinder gases of hydrocarbons, halocarbons, and sulfur species have been used successfully to assess the Industry Audit Material Cylinder Concentration Client Audit (ppm) Accuracy Maleic anhydride production Ester production Vegetable oil plant Coke oven by-product Benzene in N Propane in Air Hexane in N Benzene in N 138 300 10.1 710 82.2 1982 88.4 8.2 -9.4 +4.7 +8.6 +8.6 +5.6 +3.0 -8.7 +2.6 accuracy of gas chromatographic systems used to measure organic compounds in source emissions. Absolute accuracy has not been determined because of lack of standard reference materials; instead, interlabor- atory bias has been reported for the performance audits conducted during source testing. The interlaboratory bias determined has been generally within 10 percent for both low and high concentration gases. Twenty-six out of 40 gaseous compounds have demonstrated sufficient stability in cylinders for use as audit materials. Four compounds (ethylamine, paradichlorobenzene, cyclohexanone, and aniline) are not recommended as audit materials for various reasons as discussed in the full report. Another 10 compounds (carbon tetrachloride, methylene chloride, methyl chloroform, Freon 113, ethylene oxide, propylene oxide, alkyl chloride, acrolein, ch lorobenzene and carbondisulfide) have recently been added to the repository; the stability of these compounds remains to be studied. The estimates of stability are reported in terms of percent change per month. Detailed statistical analyses which would separate statistical deviations from true concentration change with time are in progress and will be presented in a journal publication. Table 3. Typical Stability Results Compound Concentration Period of Cylinder (ppm) Analyses (months) % Change/Month Benzene Benzene Hydrogen sulfide 1,2 Dichloroethane Perchloroethylene Acrylonitrile Chloroform Propylene 12.2 296 9.15 439 13.0 20.1 348 14.8 25 27 37 28 13 28 33 25 -0.15 0.01 -0.05 -0.10 -0.23 -1.07 -0.20 0.06 ------- R. K. M. Jayanty, W. F. Gutknecht, and C. E. Decker are with Research Triangle Institute, Research Triangle Park, NC 27709; the EPA authors J. E. Knoll and D. J. von Lehmden (also the EPA Project Officer, see below) are with the Environmental Monitoring Systems Laboratory, Research Triangle Park, NC 27711. The complete report, entitled "Stability of Organic Audit Materials and Results of Source Test Analysis Audits," (Order No. PB 83-107 490; Cost: $11.50. subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Environmental Monitoring Systems Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 •(t U.S. GOVERNMENT PRINTING OFFICE: 1983 6S9-O17/O881: United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Postage and Fees Paid Environmental Protection Agency EPA 335 Official Business Penalty for Private Use $300 5ss CHIC»eO IL 606M ------- |