United Stales Environmental Protection Agency Environmental Monitoring Systems Laboratory Research Triangle Park IMC 27711 Research and Development EPA-600/S4-84-002 Jan. 1984 Project Summary Stability of Organic Audit Materials and Results of Source Test Analysis Audits—Status Report #5 R. K. M. Jayanty, W. F. Gutknecht, C. E. Decker, J. E. Knoll, and D. J. von Lehmden A repository of 42 gaseous com- pounds including hydrocarbon, halo- carbon, and sulfur species has been established under contract with the U.S. Environmental Protection Agency (EPA). 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 or- ganic chemical manufacturing indus- tries, (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, 20 compounds have been used to conduct 106 different audits. The results of these audits and a descrip- tion 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 deter- mined through multiple analyses of the cylinders containing them. Stability values for all compounds are expressed as percent change per month. Calcu- lated changes are typically found to be a few tenths of one percent per month, though many of these changes may not be significantly different from zero. This Project Summary was developed by EPA's Environmental Monitoring Systems Laboratory. Research Triangle Park. NC, to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering in- formation at back). Introduction Accurate measurement of hydro- carbons, halocarbons, and sulfur contain- ing compounds in ambient and source samples is essential to any environmental monitoring program. The potential for achieving acceptable accuracy is en- hanced 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 (EPA), has responded to this need by developing an extensive repository of standard gaseous com- pounds. 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 42 different compounds based on antici- pated needs of EPA. Table 1 lists the compounds, the concentration ranges of each compound, and the number of cylinders of each compound. Additional compounds are obtained as needed. ------- Table 1. Audit Materials Currently Held in the Repository Low Concentration Range No. of Concentration Cylinder Compound Cylinders Range (ppm) Construction'' Benzene Ethylene Propy/ene Methane/Ethane Propane Toluene Hydrogen Sulfide Meta-Xylene Methyl Acetate Chloroform Carbonyl Sulfide Methyl Mercaptan Hexane 1,2-Dichloroethane Cyclohexane Methyl Ethyl Ketone Methanol 1,2-Dichloropropane Trichloroethylene }, 1 -Dichloroethylene 1,2-Dibromoethylene Perchloroethylene Vinyl Chloride 1,3-Butadiene A crylonitrile "Aniline Methyl Isobutyl Ketone ""Paradichlorobenzene ""Ethylamine ** Formaldehyde Methylene Chloride Carbon Tetrachloride Freon 1 13 Methyl Chloroform Ethylene Oxide Propy/ene Oxide Allyl Chloride Acrolein Chlorobenzene Carb on Disulfide ""Cyclohexanone ""EPA Method 25 Gas 14 4 4 - 4 2 4 2 2 2 2 4 2 4 - 1 1 2 2 2 2 2 9 1 ' 3 1 1 2 2 - 1 1 1 1 1 1 1 1 1 - 1 3 8-13 5-20 5-20 — 5-20 5-20 5-20 5-20 5-20 5-20 5-20 3-70 20-50 5-20 — 30-50 30-50 5-20 5-20 5-20 5-20 5-20 5-30 5-30 5-20 5-20 5-20 5-20 5-20 — 5-20 5-20 5-20 5-20 5-20 5-20 5-20 5-20 5-20 — 5-20 700-200 S Al Al - Al S Al S S S S Al Al Al - S Al Al Al Al Al S S LS.AI Al Al S Al - Al Al Al Al Al Al S Al Al Al Al Al High Concentration Range No. of Concentration Cylinder Cylinders Range (ppm) Construction'' 17 4 6 4 4 4 2 2 2 2 2 2 - 2 4 1 - - 2 2 2 2 2 - - 3 - 7 - - - - - - - - 7 7 - - 7 - 3 60-400 300-700 3000-20,000 300-700 1000-6000IM). 200-700/EI 300-700 300-700 300-700 300-700 300-700 300-700 700-300 — 7000-3000 700-600 50-200 — — 300-700 700-600 700-600 700-600 300-700 — — 300-700 — 75 — — — — — — — — 75-200 75-200 — ___ 75-200 — 750-2000 Al. S Al Al Al Al Al S Al LS S S S - LS Al S - - LS Al Al Al LS - - LS.AI - Al - - - - - - - - Al S - - Al - Al "Cylinder construction: Al - Aluminum. S = Steel, LS = Low Pressure Steel. "Cylinders are no longer available in the repository since the compounds are found to be unstable in the cylinders. """The gas mixture contains an aliphatic, an aromatic and carbon dioxide in nitrogen. Concentrations^ shown are reported in ppmC. ------- 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 com- pressed gas cylinder is especially suitable as an audit device because of its simpli- city, portability, low cost, flexibility in analyte delivery over a broad concentra- tion range, reliability, and ruggednessfor interstate shipping. The accuracy of the supplier-reported levels of these com- pounds are verified through measure- ment 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 com- mercial supplier iscontactedtodetermine if a cylinder containing that compound can be prepared. If so, the manufacturer prepares the cylinder gases and deter- mines the concentration 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 acqui- sition, and one year after acquisition. 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 detec- tor 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 measurement of audit materials. NBS-SRM's 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 measure- ment of ethylene and propylene, assum- ing 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 volatilized 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 instruc- tions 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, 106 individual audits have been initiated, and 102 are complete. The results obtained for a few typical per- formance audits are shown in Table 2 and Table 2. Typical Audit Results 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 deter- mine the stability of these compounds; some are analyzed as many as eight times. An estimate of stability has been made for each cylinder that has been analyzed at least three times. This esti- mate is a calculation of percent change in concentration per month over the period that RTI has performed analyses of the cylinder contents. The calculation in- volves a linear regression analysis of the concentration of the analyte versus time in days. The slope and intercept deter- mined by this regression analysis are then used to calculate percent change per month by the relationship % change/month = — x 100 x 30 y intercept 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 numbef of analyses per cylinder increases, additional statistical analyses will be performed. Industry Maleic anhydride production Vinyl chloride production Vegetable oil plant Degreasing vent Audit Material Benzene in N2 1,2-Dichloroethane in N2 Hexane in N2 Trichloroethylene in N2 Cylinder Concentration (ppm) 138 300 9.3 462 82.2 1982 14.9 566 Client Audit Bias 1%) -9.4 +4.7 +6.0 +3.7 +5.6 +3.0 -0.4 -8.7 Table 3. Typical Stability Results Compound Benzene Benzene Hydrogen sulfide 1,2 Dichloroethane Perchloroethylene Acrylonitrile Chloroform Propylene Concentration Period of Cylinder (ppm) Analyses (Months) 12.2 296 9.15 439 13.0 20.1 348 14.8 25 27 37 28 13 28 33 25 % Change/Month -0.15 0.01 -0.05 -O.JO -0.23 -1.07 -0.20 0.06 ------- Conclusions Cylinder gases of hydrocarbons, halo- carbons, and sulfur species have been used successfully to assess the 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 interlaboratory bias has been reportedfor the performance audits conducted during source testing. The interlaboratory bias determined has been generally within 10 percent for both low and high concentra- tion gases. Thirty-seven out of 42 gaseous com- pounds have demonstrated sufficient stability in cylinders for use as audit materials. Five compounds (ethylamine, paradichlorobenzene cyclohexane, form- aldehyde and aniline) are not recom- mended as audit materials for various reasons as discussed in the full report. 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 for 14 compounds have been recently published in a journal publication and statistical analyses for the remaining compounds are in progress and will be presented in the final report. R. K. M. Jayanty, W. F. Gutknecht, and C. E. Decker are with Research Triangle Institute. Research Triangle Park, NC 27709. J. E. Knoll and D. J. von Lehmden are the EPA Project Officers (see below). The complete report, entitled "Stability of Organic Audit Materials and Results of Source Test Analysis Audits—Status Report #5," (Order No. PB 84-128 578; 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 *U.S. GOVERNMENT PRINTING OFFICE: 1984-759-015/7 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Official Business Penalty for Private Use $300 ------- |