Envlron. Sci. Technol. 1985, 19, 749-752
(2) Mackay, D. Environ. Sci. Technol. 1982, 16, 274. (3) Lindley, D. V. J . R. Stat. SOC.,Supp. 1947, 9, 218. (4) Teisser, G. Biometrics 1948, 4 , 14. (5) Ricker, W.E. J . Fish. Res. Board Can. 1973, 30, 409. (6) Sprent, P. “Models in Regression and Related Topics”; Methuen & Co.: London,-l969; pp 1-173. ( 7 ) Kermack, K. A,; Haldane, J. B. Biometrika 1950, 37, 30. (8) Veith, G. D.; DeFoe, D. L.; Bergstedt, B. V. J . Fish. Res. Board Can. 1979, 36, 1040. (9) Mackay, D.University of Toronto, personal communication, 1984.
KBshould be 1while published regression lines are always less than 1. However, as shown in eq 17 the correct use of a regression formula allows the derivation of the theoretical expected slopes without any a priori constraints. Acknowledgments I am indebted to K. Kaiser, J. M. Ribo, and D. Mackay for fruitful discussions and comments. Four anonymous reviewers also provided useful editorial comments. Literature Cited (1) Geyer, H.; Politzki, G.; Freitag, D. Chemosphere 1984,13, 269.
Received for review June 4, 1984. Revised manuscript received December 31, 1984. Accepted February 21, 1985.
Peroxyacetyl Nltrate: Comparlson of Alkaline Hydrolysis and Chemiluminescence Methods Daniel Grosjean * and Jeffrey Harrison
Daniel Grosjean and Associates, Inc., Suite 645, 350 N. Lantana Street, Camarillo, California 93010
rn Peroxyacetyl nitrate (PAN; CH3C(0)OON02)was prepared from sunlight irradiation of organic-NOx and chlorine-organic-NOx mixtures in air, and its concentration was measured by using two methods. The first method involved ion chromatography following alkaline hydrolysis of PAN to acetate, and the second method involved PAN measurements using a chemiluminescent NO, analyzer. The two methods were found to be in good agreement in the range of PAN concentrations tested, 0-400 ppb. Applications and limitations of the two methods are discussed for both laboratory and ambient measurements of PAN. Introduction Peroxyacetyl nitrate (PAN CH3C(0)OON02)is a major product of photochemical reactions involving hydrocarbons and oxides of nitrogen in the atmosphere (1). Levels of PAN in urban areas such as Los Angeles sometimes exceed 40 ppb (2,3). PAN has been studied for its phytotoxic (4) and mutagenic (5) properties and for its importance in the long-range transport of oxides of nitrogen in the troposphere (6, 7). PAN measurements in smog chamber studies of HC-NO, reactions are essential to the development of a better understanding of these complex reactions and serve as input to the testing and validation of computer kinetic models describing the atmospheric chemistry of hydrocarbon pollutants (8, 9). We recently described a portable PAN generator and its application to on-site calibration of PAN analyzers (10). The PAN output of the generator, which can be varied in the range -2-400 ppb, was determined by ion chromatography following alkaline hydrolysis of PAN to acetate: CH&!(O)OONO2 + 20HCH3COO- + NO2- + 0 2 + H2O (1) Chemiluminescent NO, analyzers have been shown to respond to, besides NO2, a number of nitrogenous pollutants including PAN (11-13). This interference from PAN may be a serious problem when ambient levels of NO2 are monitored by using chemiluminescent analyzers (2). In turn, the chemiluminescence method can be employed for measurements of PAN under certain conditions, for example, by difference following removal of PAN in alkaline -+
0013-936X/85/09 19-0749$01.50/0
solutions (reaction 1). In this paper, we compare the alkaline hydrolysis and chemiluminescence methods with PAN prepared in situ from a number of organic-NO, mixtures. Experimental Methods Test atmospheres containing ppb levels of PAN were prepared in 4-m3outdoor chambers constructed from FEP 200A Teflon film. The matrix air was supplied by an Aadco Model 737-14 purified air generator. PAN was measured by electron capture gas chromatography (ECGC) as described before (10). The EC-GC instrument was calibrated against the output of the portable PAN generator (10). The PAN generator output was measured by ion chromatography (IC) following alkaline hydrolysis of PAN to acetate in dilute KOH impingers (10). The chemiluminescent NO, analyzer, Teco Model 14 B/E, was calibrated by gas-phase titration as is described in detail elsewhere (13). The converter efficiency (molybdenum converter, T = 450 OC) was measured as part of the calibration and was 20.98. Due to evaporation of dilute KOH solutions from the impinger, sampling lines downstream of KOH impingers should be verified and cleaned or replaced periodically. A Teflon line coated with KOH becomes a very efficient PAN denuder tube. Removal of PAN by nylon filters (Ghia, 1-pm pore size, washed with deionized water prior to use) was measured directly by EC-GC and was found to be negligible (
