Anal. Chem. 1989, 61, 2743-2746 15) Yana. F.-S.: Caldwell. K. D.; Giings, J. C. J. Colloid Interface Sci. 198% 92. 81-90. (6) Yang, F.-S.; Caldwell, K. D.; Myers, M. N.; Gddings, J. C. J. Colloid Interface Sci. 1983, 9 3 , 115-125. (7) Yau, W. W.; Kirkland, J. J. Sep. Sci. Technol. 1981, 16, 577-605. (8) Kerker, M. The Scattering of Light; Academic Press: New York, 1969. (9) Giings, J. C. J. Chem. Educ. 1973, 5 0 , 667-669. (10) Giddings, J. C. J . Chem. Phys. 1968. 49, 81-85. (11) Giddings. J. C.; Yoon, Y. H.; Caldwell, K. D.; Myers, M. N.; Hovingh, M. E. Sep. Sci. 1975, 10, 447-460. (12) Schimpf, M. E.; Myers, M. N.; Giddings, J. C. J . Appl. Polym. Sci. 1987, 3 3 , 117-135. (13) Gddings, J. C.; Yang, F. J. F.; Myers, M. N. Anal. Chem. 1974, 46, 1917-1924. (14) Karaiskakis, G.; Myers, M. N.; Caldwell, K. D.; Giddings, J. C. Anal. Chem. 1981. 5 3 , 1314-1317. (15) Giddings, J. C.; Schure, M. R.; Myers, M. N.; Velez. G. R. Anal. Chem. 1984, 5 6 , 2099-2104. (16) Giddings, J. C.; Schure, M. R. Chem. Eng. Sci. 1987, 4 2 , 1471-1479. (17) Williams, P. S.; Giddings, S. B.; Giddings, J. C. Anal. Chem. 1986, 5 8 , 2397-2403. (18) Schure, M. R. Anal. Chem. 1988, 60, 1109-1119. (19) Tung, L. H. J . Appl. Polym. Sci. 1969, 13, 775-784. (20) Kirmse, D. W.; Westerberg, A. W. Anal. Chem. 1971, 4 3 , 1035-1039. (21) Rosen, E. M.; Provder, T. Sep. Sci. 1970, 5 , 485-521. (22) Jahnovi, V.; Matulik, F.; Janca, J. Anal. Chem. 1987, 5 9 , 1039- 1043. (23) Schimpf, M. E.; Williams, P. S.; Giddings, J. C. J . Appl. Polym. Sci. 1989, 37. 2059-2076. (24) Jansson, P. A. Deconvolution with Applications in Spectroscopy; Academic Press: New York, 1984. (25) Ishige. T.; Hamlelec, A. E. J . Appl. Polym. Sci. 1971, 15, 1607-1622. ~I
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(26) Alba, D.; Meira, G. R. J. Li9. Chromatogr. 1984, 7 , 2833-2862. (27) Bevington, P. R. Data Reduction and Error Analysis for the Physical Sciences; McGraw-Hill: New York, 1969. (28) Savitsky, A.; Golay, M. J. E. Anal. Chem. 1984, 36, 1627-1639. (29) Steinier, J.; Termonia, Y.; Deltour, J. Anal. Chem. 1972, 44, 1906- 1909. (30) Madden, H. H. Anal. Chem. 1978, 50, 1383-1386. (31) Schure, M. R. Sep. Sci. Technol. 1987, 72, 2403-2411. (32) Bohren, C. F.; Huffman, D. R. Absorption and Scattering of Light by Small Particles; Wiley: New York, 1983; Appendix A. (33) Bracewell, R. N. The Fourier Transform and Its Application; McGrawHill: New York, 1978. (34) Brigham, E. 0. The Fast Fourier Transform; Prentice-Hall: Englewood Cliffs, NJ, 1974; Chapter 9. (35) Jones, H. K.; Barman, B. N.; Giddings, J. C. J. Chromatogr. 1988, 455, 1-15. (36) Gajdos, L. J.; Brenner, H. Sep. Sci. Technol. 1978, 13, 215-240. (37) Glddings, J. C.; Barman, B. N.; Li, H. J . Colloid Interface Sci., in press. (38) Bangs, L., private communication. (39) Yau, W. W.; Kirkland, J. J. Anal. Chem. 1984, 56, 1461-1466. (40) Giddings, J. C. Anal. Chem. 1986, 5 8 , 735-740. (41) Hansen, M. E.; Gddings, J. C.; Schure, M. R.; Beckett, R. Anal. Chem. 1988. 60. 1434-1442. (42) Giddings, J. C.; Williams. P. S.; Beckett, R. Anal. Chem. 1987, 5 9 , 28-37. (43) Williams, P. S.; Giddings, J. C. Anal. Chem. 1987, 59, 2038-2044.
RECEIVED for review April 21, 1989. Accepted September 15, 1989. Part of this study was presented at the 190th meeting of the American Chemical Society, Chicago, IL, September 1985. This work was supported by Grant CHE-8800675 from the National Science Foundation.
Determination of Acrylonitrile in Stationary Source Emissions by Impinger Sampling and Gas Chromatography with Nitrogen-Phosphorus Detection James N. Fulcher, Gary B. Howe,* R. K. M. Jayanty, and Max R. Peterson Center for Environmental Measurements, Research Triangle Institute, P.O. Box 12194,
Research Triangle Park, North Carolina 27709 Jimmy C. Pau, J. E. Knoll, and M. R. Midgett
U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711 Acrylonitrile (AN) has been identified as a suspected carcinogen and may be regulated in the future as a hazardous air pollutant under Section 112 of the Clean Air Act. A method for sampling and analysis of AN in statlonary source emisdons has been developed and evaluated through both laboratory and Reid testing. I n thls method, a mklget impinger containing methanol followed by a back-up sorbent tube containing activated charcoal is used to trap AN vapor. Analysis is performed by capillary column gas chromatography with a nitrogen-phosphorus detector (NPD). The percentage accuracy of the method is 4.6% based on laboratory tests covering the range of 10.6-1038 ppm AN and 0-40% moisture by volume at 100 OC. The precision of the method in laboratory tests, expressed as a pooled relative standard deviation, was 3.3%. The precision of the method in field tests at two different sites was 1.9% and 2.4% (pooled relative standard deviation), respectively. The instrumental limit of detection for acrylonitrile in methanol was determined to be 0.051 ng/pL.
INTRODUCTION The U.S. Environmental Protection Agency (USEPA),
Research Triangle Park, NC, has a program to evaluate and standardize source testing methods for hazardous pollutants in anticipation of future regulations. The Research Triangle Institute (RTI) was recently contracted by the USEPA to develop and evaluate a sampling and analysis method for acrylonitrile (AN) emissions from stationary sources. A test method based on National Institute for Occupational Safety and Health (NIOSH) Method 1604 (1) was developed earlier by another EPA contractor (2). This method used charcoal tubes to adsorb the compound during sampling, followed by solvent desorption and gas chromatographic analysis with flame ionization detection (GC/FID). Hydrocarbon interference and the presence of water vapor in the source have been detrimental to the effectiveness of the method, reflected primarily in poor accuracy a t low concentrations of AN. Poor accuracy and recovery at low levels of acrylonitrile on charcoal have also been documented in other work (3). In the present study, two modifications were investigated. The first was the use of an impinger to remove most of the water from the sample stream before it reaches the charcoal tube. The second modification was the use of a nitrogen-phosphorus detector (NPD), rather than an FID, in the analysis of the samples. The NPD was chosen for this study because it responds selectively to nitrogen- and phosphorus-containing compounds
0003-2700/89/0361-2743$01.50/0 0 1989 American Chemical Society
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ANALYTICAL CHEMISTRY. VOL.
61.
NO. 24, DECEMBER 15, 1989
Teflon 114" Swagelok
Tubing
Dmar and b e
Flgure 1. Acrylonitlile sampling apparatus. (4). Generally, a very weak response is obtained with compounds that do not contain these elements. The new method was evaluated initially in the laboratory to determine the precision, acmacy, and detection limits. After the laboratory evaluation, the method was tested in the field at two different sites. The first field test was conducted at an acrylic fiber manufacturing plant (site A) where AN was used as a raw material. The second test was performed at an AN manufacturing facility (site B). Samples were collected over a two-day period a t each location This paper describes the development of this method in both laboratory and field studies. Further details of the evaluation are contained in a project report (5).
EXPERIMENTAL SECTION Apparatus. Test mixtures of acrylonitile in dry or humidified nitrogen were produced for use in the present study. These mixtures were generated with a dynamic dilution system consisting of a pressurized stainless steel sphere of AN in dry nitrogen (1W3000 ppm), a heated glass mixing bulb, a heated glass sampling manifold, and m a s flow control of diluent nitrogen and AN in nitrogen gas flows. When required, a threeneck flask containing organic-free water and housed in a heating mantle was used to humidify the diluent nitrogen. The pressurized sphere of AN vapor in nitrogen was produced a t RTI using a gas standard preparation system. This system consists of a six-port rotary valve fitted with a calibrated volume stainless steel loop for injecting pure AN liquid, a high-precision hourdon-tube vacuum/pressure gauge (Heise Model CMM), a vacuum pump, and a high-pressurecylinder of clean, dry nitrogen. The accuracy of this system in producing gas standards has been established previously and is described in a separate publication (6).
Sampling apparatus consisted of a 25" midget impinger, a w u u t charcoal tube with an W m g front section and a 2oO-mg hack section, and a low flow air sampling pump (SKC Model 222-3). A schematic of the acrylonitrile sampling train is shown in Figure 1. The sampling trains were connected to the sampling manifold during laboratory testing with I/, in. 0.d. Teflon tubing. During field testing a site A, in. 0.d. stainlesa steel tubing was used as a sample probe for each sampling train. A stainless steel manifold was used at site B and sample trains were connected to the manifold with I/, in. 0.d. Teflon tubing. Samples were analyzed with a HewlettPackard Model 5880A gas chromatographequipped with a nitrogen-phosphorusdetector and a split/splitless capillary injector. Laboratory samples and site A samples were injected onto a 30 m X 0.25 mm i.d. DB-WAX fused silica capillary column (0.5-pm film thickness). Site B field test samples were injected onto a 30 m X 0.55 mm i.d. DB-WAX fused silica capillary column (1.0-Fm film thickness), Procedure. Tests of the precision and amracy of the propeed method were performed in the laboratory by using test mixtures generated with the dynamicdilution system. The mixtures ranged in acrylonitrileconcentration from 10.8to 1038 ppm and in water vapor concentration from 0 to 40% by volume at 100 OC. During
a given test, concentrated acrylonitrile in dry nitrogen from a preasurked canister was metered into a spherical 1-Lglass mixing bulb located in a heated enclmure. Diluent nitrogen was metered ink, the bulb simultaneously. and the concentration of AN in the dilution system manifold was calculated from the two flow rates and the cnnrentratinn of the gas in the source canister. For some tests. water vapor was introduced to the tent mixture by passing the dduent nitrugen through a heated flask containing onanic-free water. The water vapor concentration was calrulated from two gas flow rates and the water temperature. During each test, three samples were collected simultaneously from the glans manifold. Each sampling train consisted of an impinger containing 25 mL of chromatographic grade methanol, a charcoal rube, and a sampling pump in series. The impingem were placed in Dewar flaskscontaining ice water. Prior to sampling, the dilution system was allowed to equilibrate. Following this. sampling was carried out for 1 h at a nominal rate of SO mL/min. Flow rates were measured with a soapfilm flowmeter before and after each test. After sampling, the charcoal tubes were removed and capped, and the impinger solutions were transferred to glass storage vials with severnl solvent rinses. Before analysis, 5 pL of valeronitrile was added as an internal standard to each impinger solution. (:harcoal tubes were desorkd with IO mL of 2% formic acid in methanol. The desorbing solutions werealsospiked with the valeronitrile internalstandard. Samples were analyzed by gas chromatography with nitrogenphosphorus detection. Helium carrier gas was supplied at a flow rate 01' 1.3 ml./min (measured at 60 ' C column temperature). Detector hydrogen and air were supplied at 6.5and 85 mL/min. respectively. A helium flow of 30 mL/min was used for carrier make-up gas. The detector temperature was 240 "C and the injector temperature was 250 "C. Injections of 1-ULsample aliquots were performed with a split ratio of 601. The column temperature prugram was 60 O C for 3 minutes, S "C/min to 100 "C, LOO "(: for I min. Detector linearity was evaluated for acrylonitrile over a range of concentrations (l(t3840 ppm) and was found to be excellent (log area vs log concentration yielded a slope of 1.006 and a correlation coefficient of 0.999921. The instrumend limit of detection (LOD) was determined by using the single sample method (7). A solution of A N at a concentration of approximately twice the estimated limit of quantitation (obtained from literature valued was analyzed nine ronsecutive times. The standard deviation of the detector response was then multiplied by 3 to ohtain the response at the LOD. The LOD was calculated by applying the detector calibration factor tu this response. The procedure for sample collection and analysis during field testing was similar to that of the laboratory evaluation. Six sampling runs were performed on each of two days at site A with four samples collected in parallel during each run. Source gas containing acrylonitrile vapor was introduced into each sample train through a I . in. 0.d. stainless steel probe inserted through the wall of an exhaust vent on the plant roof. After sampling, impinger solutions and charcual tubes were stored on ice during retum to the lahoratory for analysis. Each impinger sample was analyzed as desrribed previously and one charcoal tube was selected at random from each run for analysis. At site B, source gas effluent from a wet scrubber wan pumped to a stainlfis steel sampling manifold to which low sampling trains were connected. Seven sampling NIWwere performed on the first day and six on the second day. Sample analysis procedures were identical with thme used for Site A field samples except that a wide-hre capillary column was used to increase injection volume capacity and nllow measurement of the lower concentrations. Chromatographic conditions were the same as those used with the narrow bore column except for a helium carrier gas flow rate of 5.6 ml./min and the use of a split/splitlew,injection technique. The splitless period was 12. sand the injector liner was purged during the split mode with 120 mL/min of helium. RESULTS AND DISCUSSION Accuracy and Precision Tests. 7 h e results of laboratory tests to determine the accuracy and precision of the proposed method are shown in Table 1. The measured acrylonitrile concentrations are based on calculations from the impinger
ANALYTICAL CHEMISTRY, VOL. 61, NO. 24, DECEMBER 15, 1989
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Table I. Accuracy and Precision Test Results run no. 1 2 3 4 5 6 7 8 9 10
H 2 0 vapor concn, %
true AN concn, ppm
0 0
10.8 1000 10.7 10.6 10.7 10.9 107 101 98.6 513 1038
30 20 30 33 32 32 32 40 32
11
measured AN concn, ppm imp A imp B imp C 9.72 980 9.95 10.1 9.63 10.4 107 104 104 508 996
9.72 980 10.0 10.2 9.63 11.6 125 103 102 503 986
-
% accuracy
9.94 990 10.2 10.3 9.74 10.9 108 106 104 503 1007
% RSD 1.3 0.6 1.3 1.0 0.7 5.5 8.9 1.5
-9.3
-1.7 -6.1 -3.8 -9.7 0.6 5.9 3.3 4.8 -1.6 -4.0
1.1 0.6 1.0
Table 11. Site A Field Test Results
Table 111. Site B Field Test Results
AN Source Concn, ppm run no. imp A imp B imp C impD mean stddev % RSD
AN source concn. m m run no. imp A imp B imp C imp D mean std dev 70 RSD
1 2 3 4 5 6 7 8 9 10
11 12
-
105 108 109 109 111 110 84.0 83.8 83.2 84.3 74.9 102
112 108 109 109 113 82.8 85.1 83.5 80.2 73.8 102
111 112
111 111 111 114 85.7 87.4 85.4 85.1 76.8 104
107 108 109 109 110 110 82.5 86.9 81.7 84.4 74.1 101
109 109 110 110 110 112 83.8 85.8 83.4 83.5 74.9 102
3.3 2.0 1.0 1.5 1.0
2.1 1.4 1.7 1.5 2.2 1.3 1.3
3.04 1.83 0.91 1.39 0.87 1.84 1.73 1.93 1.82 2.67 1.80 1.23
solution analysis and sample gas volume collected. Analysis of the desorbed charcoal tube samples showed insignificant (less than 1%) breakthrough of the impingers. The percentage accuracy of the mean concentration is shown for each run. The overall average percentage accuracy is 4.6 %. The relative standard deviation of the triplicate samples ranged from 0.6 to 8.9%. The overall method precision, expressed as the pooled relative standard deviation, is 3.3%. T o test the effect of moisture on precision and accuracy, logarithmic transformations were carried out, and means, standard deviations, and deviations from the prepared values were calculated. Linear regression of the standard deviations on the means showed that the standard deviations were not level dependent (calculated t statistic, 0.32; critical value, 2.62). Linear regression of the deviations from the prepared values on the H 2 0 concentrations failed to show any correlation (calculated t statistic, 1.27; critical value, 2.62). Application of the Bartlett test (8)to the standard deviations showed that the variances were not homogeneous (calculated x2 statistic, 3.09; critical value, 16.9). The pooled standard deviation calculated from the remaining data was 0.0086, which corresponds to a coefficient of variation of 0.9%. The lack of correlation of the deviations with moisture content and the constancy of the variances are indications that moisture did not affect the measurements significantly. A test of the mean of the transformed deviations yielded a t-statistic value of 7.49, which when compared with the critical value, 2.20, indicated that the mean was significant a t the 95% confidence level. It corresponded to a negative bias of 2.2%. Limit of Detection. The average concentration of acrylonitrile determined for a low concentration solution of acrylonitrile in methanol based on nine injections was 0.459 nglpL with a standard deviation of 0.017 ng/pL. The limit of detection is then 0.051 ng/pL which is equivalent to 0.192 ppm in air for a 3-L air sample with AN collected in 25 mL of methanol.
1 2' 3" 4 5 6 7 8 9 10
11 12 13
23.2 15.7 26.3 28.3 28.0 27.4 33.6 32.9 38.2 43.5 42.4 44.1 46.6
22.5 17.5 19.3 27.0 26.5 26.3 30.6 31.5 38.1 44.9 41.0 43.4 46.0
23.5 25.9 28.2 26.0 26.9 32.7 32.9 38.6 41.5 42.4 43.6 46.6
23.3 20.6 25.7 27.8 26.7 27.2 33.6 32.3 38.5 41.3 41.4 43.4 46.0
23.1
0.46
2.0
27.8 26.8 27.0 32.6 32.4 38.4 42.8 41.8 43.6 46.3
0.58 0.86 0.46 1.40 0.65 0.27 1.74 0.71 0.30 0.32
2.1 3.2 1.7 4.3 2.0 0.7 4.1 1.7 0.7 0.7
a Results discarded due to problems with sampling manifold flow during samde collection. ~~
Site A Field Test. The results of analyzing impinger samples from site A are shown in Table 11. Excellent method precision was achieved with the highest relative standard deviation of 3.04% occurring in run no. 1. Linear regression of the standard deviations versus the means showed that the values were not level dependent. Application of the Bartlett test showed that the standard deviations were homogeneous; therefore, it was possible to calculate a pooled standard deviation that was more representative of the data than the standard deviation of any single run (6). This value was 1.8 ppm (1.9% relative standard deviation). Concentrations determined from analysis of one charcoal tube from each sampling run were 1%or less of the total concentration measured. This agrees well with the results obtained in the laboratory evaluation. Site B Field Test. Results of the analysis of impinger samples from site B are shown in Table 111. Excellent precision was again achieved with the highest percent relative standard deviation at 4.3% for run no. 7. Application of the statistical methods cited above showed that the standard deviations in Table I11 were also homogenous; the pooled standard deviation was 0.84 ppm (2.4% relative standard deviation). Concentrations determined from analyzing charcoal tubes from selected runs were again less than 1% of the total concentration. Stability Study. A study of acrylonitrile stability in methanol was performed by preparing and analyzing four solutions containing AN a t levels near that observed in the site A field test samples. Two of the solutions contained 36 ppm of 4-methoxyphenol as an inhibitor to AN polymerization. Each solution was analyzed immediately after preparation, after 2 days, and then after 2 weeks. The study results are shown in Table IV. The data indicate that AN in
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ANALYTICAL CHEMISTRY, VOL. 61, NO. 24, DECEMBER 15, 1989
T a b l e IV. A c r y l o n i t r i l e in M e t h a n o l Stability Study Results measured acrylonitrile concn, n g / p L solvent
initial
2 days
2 weeks
methanol methanol methanol w i t h inhibitor methanol w i t h inhibitor
33.7 33.4 33.9 34.3
34.1 34.6 34.4 34.4
34.7 34.5 33.8 34.9
methanol at about 35 ng/pL, either with or without inhibitor, is stable for a t least two weeks.
CONCLUSIONS A simple, inexpensive, and accurate method for the determination of AN emission from stationary sources has been developed. The method has demonstrated a high level of precision that appears to be unaffected by moisture levels as high as 40% by volume at 100 "C and is applicable over a wide range of AN concentrations (10-1000 ppm). Acrylonitrile in methanol either with or without inhibitor was found to be stable for a t least two weeks. There are two major advantages of this new method. First, acrylonitrile is trapped in methanol contained in an impinger instead of a charcoal tube, avoiding the problems with poor trapping efficiency and low analytical recovery of acrylonitrile sampled with charcoal. The backup charcoal tube specified in this new method is used only as an indicator of impinger breakthrough and could possibly be omitted or substituted with another impinger. Second, the specificity of the NPD
avoids the problem of hydrocarbon interference with detection by FID.
LITERATURE CITED (1) Acrylonitrile, Method 1604 (2115184). I n NIOS,Y Manual of Analyiical Methods, 3rd ed.; Eller, P. M.. Ed.; Vol. 1. DHHS (NIOSH) Publ. 84100; U.S. Department of Heaith and Human Services: Washington, DC, 1984. (2) Bernstiel, T. J.; Daly, M. D.; Nunn, A. B., 111; Reckner, L. R. Evaluation of Charcoal Tube Adsorption for Measurement of Acrylonitrile Emissions from Stationary Sources. USEPA Contract No. 68-02-3405. Scott Environmental Technology, Inc. (3) Gagnon, Y.; Posner, J. Recovery of Acrylonitrile from Charcoal Tubes at Low Levels. Am. Ind. Hyg. Assoc. J. 1979, 40, 923-925. (4) Cooper, S. W.; Jayanty, R. K. M.; Knoll, J. E.; M i t t , M. R. Determination of Selected Nitrogen-Containing Hazardous Pollutants in Complex Matrices by Gas Chromatography with a Nitrogen-Phosphorous Detector. J. Chromatogr. Sci. 1986, 24, 204-209. (5) Fulcher, J. N.; Howe, G. 8.; Jayanty, R. K. M.; Peterson, M. R. Development and Validation of a Test Method for Acrylonitrile Emissions. US EPA Contract Nos. 66-02-4125 and 68-02-4442. Research Triangle Institute. (6) Howe. G. B.; Albritton, J. R.; Tompkins, S. B.; Jayanty, R. K. M.; Decker. C. E. Stability of Parts-Per-Million Organic Cylinder Gases and Results of Source Test Audits. USEPA Contract No. 68-02-4550. Research Triangle Institute. (7) Quality Assurance of Chemical Measurements, 2nd printing; Taylor, J. K., Ed.; Lewis Publishers, Inc.: Chelsea, MI, 1987; p 81. (8) Duncan, A. J. Quality Control and Industrial Statistics, 3rd ed.; Richard D. Irwin, Inc.: Homewood, IL, 1965; p 642.
RECEIVED for review June 30,1989. Accepted September 29, 1989. Although the research described in this article has been funded wholly or in part by the United States Environmental Protection Agency through Contract nos. 68-02-4125 and 68-02-4442 to Research Triangle Institute, it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.
