Envlron. Sci. Technol. 1984, 18, 113-116
Herron, J. T.; Huie, R. E.; Hodgeson, J. A., Eds. NBS Spec. Publ. (U.S.) 1979, No. 557. Atkinson, R.; Lloyd, A. C. J. Phys. Chem. Ref. Data, in press. “Handbook of Chemistry and Physics”, 61st ed.; Weast, R. C., Ed.; CRC Press, Inc.: Boca Raton, FL, 1980-1981. Mackay, D.; Bobra, A.; Chan, D. W.; Shiu, W. Y. Environ. Sci. Technol. 1982, 16, 645. Atkinson, R.; Aschmann, S. M.; Winer, A. M.; Pitts, J. N., Jr. Int. J. Chem. Kinet. 1982, 14, 507. Atkinson, R.; Aschmann, S. M.; Carter, W. P. L.; Winer, A. M.; Pitts, J. N., Jr. Int. J. Chem. Kinet. 1982,14, 781. Doyle, G. J.; Bekowies, P. J.; Winer, A. M.; Pitts, J. N., Jr. Environ. Sci. Technol. 1977, 11, 45. Atkinson, R.; Plum, C. N.; Carter, W. P. L.; Winer, A. M.; Pitts, J. N., Jr. J. Phys. Chem., in press. Greiner, N. R. J. Chem. Phys. 1970,53, 1070. Atkinson, R.; Carter, W. P. L.; Aschmann, S. M.; Winer, A. M.; Pitts, J. N., Jr. Znt. J. Chem. Kinet., in press. Stuhl, F. 2. Naturforsch. 1973,28A, 1383. Perry, R. A.; Atkinson, R.; Pitts, J. N., Jr. J. Chem. Phys. 1976, 64, 5314. Paraskevopoulos, G.; Nip, W. S. Can. J. Chem. 1980, 58, 2146.
(16) Lorenz, K.; Zellner, R. Ber. Bunsenges. Phys. Chem. 1983, 87, 629. (17) Zetzsch, C. 15th International Conference on Photochemistry, Stanford, CA, June 27-July 1, 1982, Abstract A-11. (18) Perry, R. A.; Atkinson, R.; Pitts, J. N., Jr. J. Phys. Chem. 1977, 81, 1607. (19) Wahner, A.; Zetzsch, C. “Proceedings of the 2nd European Symposium on the Physico-Chemical Behavior of Atmospheric Pollutants, 1981”; Reidel, Dordrecht, 1982; pp 138-148. (20) Tuazon, E. C.; Carter, W. P. L.; Atkinson, R.; Pitts, J. N., Jr. Znt. J. Chem. Kinet. 1983,14619. (21) Atkinson, R.; Darnall, K. R.; Pitts, J. N., Jr. J. Phys. Chem. 1978,82,2759.
Received for review May 19,1983. Accepted August 15, 1983. This research has been supported by the U.S. Environmental Protection Agency under Cooperative Agreement CR-809247-01 (Project Monitor, Bruce W. Gay, Jr.). Although the research described in this article has been funded by the Environmental Protection Agency, it has not been subjected to Agency review and therefore does not necessarily reflect the view of the Agency, and no official endorsement should be inferred.
Field Compatible Calibration Procedure for Peroxyacetyl Nitrate Michael W. Hoidren” and Chester W. Spicer Battelle, Columbus Laboratories, Columbus, Ohio 4320 1
rn A field compatible calibration procedure for generating ppb levels of peroxyacetyl nitrate is presented. The procedure is based upon the condensed-phase synthesis of peroxyacetyl nitrate (PAN) in octane solution. These solutions show PAN loss of 4%month-l when stored at -20 “C. The dilute PAN solutions are injected directly into known volumes of air in Tedlar bags to obtain ppb gasphase concentrations. The addition of low levels of NO2 into the bags stabilizes PAN in the gas phase. ~
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Introduction Peroxyacetyl nitrate (PAN) is a product of photochemical reactions between hydrocarbons and NO, in ambient air. PAN is also an eye irritant and a phytotoxicant. Because of these properties, it has been studied for many years, since its discovery and preliminary naming as “Compound X” by Stephens et al. (1). Smog chamber studies have shown that many C3 and higher hydrocarbons, including aromatic compounds, produce PAN when irradiated in the presence of NO,. Because of PAN’S reversible thermal decomposition and that reaction’s sensitivity to the ambient N 0 2 / N 0 ratio ( 2 , 3 ) ,it has been speculated that PAN may serve as a reservoir for NO2 and peroxy radicals and thereby play a significant role both in the atmospheric nitrogen cycle and in tropospheric ozone formation (3, 4). Due to the central role of PAN in several important aspects of atmospheric chemistry, the need exists for accurate, field-compatible measurement and calibration techniques for this compound. PAN measurements have generally been performed with a gas chromatograph coupled to an electron capture detector. Such a system is relatively portable for field use and exhibits extremely good sensitivity toward electrophilic compounds like PAN; however, the preparation of calibration standards for this detection system is not straightforward. Pure liquid PAN 0013-936X/84/0918-0113$01.50/0
is explosive, and preparation of dilute gaseous standards is complicated by the compound’s instability. PAN’S highly temperature-dependent decay rate (2,3)eliminates the possibility of storing low-concentration gas standards for more than a few hours. Several calibration procedures have been employed by researchers making PAN measurements in the field. One approach involves preparation of gaseous ppm-level PAN mixtures in metal cylinders or Teflon/Tedlar bags. The concentration of PAN in these samples is determined by infrared spectroscopy at a central laboratory, followed by transport of these “calibrated” mixtures to the field site. However, significant PAN losses can occur when these containers are subjected to ambient temperature changes (5). A colorimetric procedure reported by Stephens (6) provides an alternative field calibration method, but high PAN concentrations are needed for adequate color development. A calibration procedure based on the thermal decomposition of PAN in the presence of NO has also been reported (5). It involves the stoichiometric reaction of PAN with NO in the presence of excess benzaldehyde. Benzaldehyde serves to control the OH radical chemistry arising from the reaction, and its inclusion results in more precise PAN calibrations. However, Lonneman et al. suggest that this procedure is not highly accurate and is most appropriate for approximate values of PAN. Recently, several procedures for the condensed phase synthesis of PAN have been described (2, 7,8). Nielsen et al. (8) have shown that gas chromatographic (GC) calibrations can be accomplished once the synthesized PAN is purified by liquid chromatographic procedures. These authors determine PAN concentration by hydrolysis and ion chromatographic analysis of nitrate and nitrite ions. In this work, we make use of a similar preparation procedure for dilute PAN solutions (7). However, we find that liquid chromatographic cleanup procedures are not necessary to obtain high-purity PAN samples. We determine
0 1984 American Chemical Society
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Table I. Absorptivity Values for PAN in Octane Solution, & 5 50-pm Cell (KBR Plates) wavenumber, cm-
absorptivity, gm-' (pg/iA)-'
1830 1728 1294 1153 787
0.0004 1 0.0011 5 0.00041 0.00042 0.00044
I
'
the concentration of PAN in solution directly, using liquid IR cells and derived absorptivity values. The PAN/octane solutions are quite stable, and the results reported here demonstrate that the mixtures can be transported to field sites for subsequent liquid- or gas-phase dilution for ppb-level gas chromatographic calibrations.
Experimental Section The PAN synthesis was accomplished as follows. A 100-mL three-necked flask equipped with a condenser, thermometer, and magnetic stirring bar was flushed with Nz and charged with 60 mL of N2-flushedoctane (Burdick & Jackson). The flask was then placed in a dry ice-acetone bath and maintained at 0 "C. Peracetic acid (40% in acetic acid; FMC Corp.; 1.2 mL) was added, followed by concentrated sulfuric acid (4 mL; Baker). Powdered sodium nitrate was then slowly added such that the temperature remained
