Environ. Sci. Technoi. 1987, 27, 503-505
In the process, the pair of electrons left by the carbon monoxide converts the palladium(I1) to finely divided palladium(O), which is black. The hue of the original light yellow complex becomes darker in proportion to the amount of palladium metal produced, which in turn is proportional to the amount of carbon monoxide that has reacted with the palladium(I1) complex. As in other methods based on palladium(II), interference will be observed from gases that precipitate palladium(II), such as hydrogen sulfide, or reduce palladium(I1) to the metal. Normally such gases are present in the atmosphere in much lower concentrations than carbon monoxide. Registry No. [Pd(CH,CONH,),](BF,),, 630-08-0.
(9) (10) (11) (12)
106905-52-6; CO,
Literature C i t e d (1) Ciuhandu, G. Fresenius' 2. Anal. Chem. 1957,. 155, 321. (2) Christman, A. A.; Block, W. D.; Schultz, J. Ind. Eng. Chem. 1937, 9, 153. (3) Lambert, J. L.; Hamlin, P. A. Anal. Lett. 1971, 4 , 745.
(13)
Lambert, J. L.; Weins, R. E. Anal. Chem. 1974, 46, 929. Lambert, J. L.; Chiang, Y. C. Anal. Chem. 1983,55, 1829. Main-Smith, J. D. Royal Aircraft Establishment Report Ch 324; HMSO: London, August 1941. Shepard, M. Anal. Chem. 1947,19, 77. Shepard, M.; Schuhman, S.; Kilday, M. V. Anal. Chem. 1955, 27, 380. Main-Smith, J. D.; Earwicker, G. A. Br. Patent 582 184, Nov. 7, 1946. Liaw, Y.-L. Ph.D. Dissertation, Kansas State University, 1985. Wayland, B. B.; Schramm, R. F. Inorg. Chem. 1969,8,971. Lambert, J. L.; Beyad, M. H.; Paukstelis, J. V.; Chejlava, M. J.; Chiang, Y. C. Anal. Chem. 1982,54, 1227. Lambert, J. L.; Paukstelis, J. V.; Liaw, Y.-L.; Chaing, Y. C. Anal. Lett. 1984, 17, 1987.
Received for review March 10,1986. Accepted December 19,1986. This research was supported in part by National Science Foundation Grant CHE-8311011 and by NSF Grant SPI8013291 t o Y.C.C.
Phenoxazlne as a Solid Monitoring Reagent for Ozonet Jack L. Lambert,* Yun-Long Llaw, and Joseph V. Paukstells Department of Chemistry, Kansas State University, Manhattan, Kansas 66506
w Phenoxazine exhibits selectivity for reaction with ozone in concentrations normally found in air to produce a brown color of exceptional stability. It reacts with nitrogen dioxide to form a red-orange product that is visually distinct from the dull brown produced by the reagent with ozone. The solid reagent on cellulose paper is intended for visual comparison to prepared color standards in passive monitoring or warning devices. Introduction
Tin(I1)-diphenylcarbazide was reported as a solid reagent responsive to the two common strong atmospheric oxidants of concern-ozone and nitrogen dioxide (1, 2). Our efforts to develop or discover reagents for passive monitoring devices that would be specific either for ozone or for nitrogen dioxide produced 1-methylperimidine as a specific reagent for nitrogen dioxide (3). A fortuitous observation during the course of other research on reagents for monitoring devices led to the development of phenoxazine as a selective reagent for ozone. Phenoxazine forms a dull brown color on reaction with ozone that appears to be stable indefinitely. On reaction with nitrogen dioxide, a red-orange color is formed that is visually quite distinct from the brown color produced by ozone. Experimental Section
Reagent Papers. Phenoxazine (Aldrich, 97% purity) is supplied as a nearly colorless compound that does not develop discoloration on standing in a sealed container. Reagent papers were prepared by wetting Whatman No. 'This paper was presented at the 190th National Meeting of the American Chemical Society, Chicago, IL, Sept. 8-13, 1985, as CHAS 11. 0013-936X/87/0921-0503$01.50/0
2 filter paper (4.25-cm circles) in a solution of 0.10 g of phenoxazine in 5.0 mL of ACS certified grade acetone (Fisher), drying at room temperature under vacuum, and storing in a sealed bottle. A study of available compounds chemically similar to phenoxazine revealed no response to ozone comparable to that of phenoxazine. Ozone Generator. Known concentrations of ozone were produced by an MEC 1000 ozone generator (Columbia Scientific Industries Corp.), which was calibrated by the neutral potassium iodide method ( 4 ) . The reagentimpregnated paper circles were exposed to various concentrations of ozone in the modified inverted Kimble low-form cap-style weighing bottle described by Lambert et al. (2). This 55-mm i.d. bottle has inlet and outlet ports for the airstream. Reflection Absorbance Measurements. A PerkinElmer Model 124 visible-ultraviolet spectrophotometer modified for reflection measurements as described by Lambert et al. (2, 4 ) was used. In this instrument, the incident beam from the light source is deflected onto the reagent paper surface and then back to its original path to the photomultiplier tube. The loss of incident radiant energy is read as absorbance in the usual manner. Reflection absorbance values at 500 nm were plotted against fixed ozone concentrations ranging from 0.083 to 0.55 ppm for various exposure times ranging from 5 to 90 min and against fixed exposure times for various ozone concentrations. Chemical Nature of the Reaction Product. A sample of the reaction product prepared by exposing a thick layer of reagent to approximately 1ppm ozone in an airstream for 3 days was ground to form a nujol mull. The infrared absorption spectra for the unexposed reagent and the reaction product, both in nujol mulls on silver chloride plates, were compared. Also, the reaction product sample prepared by passing approximately 1 ppm ozone in an air-
0 1987 American Chemlcal Society
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0.4
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Figure 3. Reagent response at 500 nm to the product of the ozone concentration and exposure time. Each point represents the average of five determinations. Flow rate of the airstream was 1 L/min. The sensitivity of the reagent is the inverse of the slope of the straight line shown, which is 44.2 ppm min (unit absorbance)-’ for 2.5 mg of phenoxazine.
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Flgure 1. Reagent response at 500 nm to several fixed ozone concentrations at various exposure times. Each point represents the average of five determinations. Flow rate of the airstream was 1 L/min.
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Figure 4. Reagent response at 500 nm to the square root of the product of ozone concentratlon and exposure time. The sample correlation coefficient r 2 was found to be 97.6%.
.-0 -al L
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Figure 2. Reagent response at 500 nm at several fixed exposure times to varlous ozone concentrations. Each polnt represents the average of five determinations. Flow rate of the airstream was 1 L/min.
stream through the reagent dissolved in chloroform for 3 days and evaporating to dryness was compared to the unreacted reagent in the same manner. In addition, mass spectra, 400-mHz NMR spectra, and ESR spectra of the 504
Environ. Sci. Technol., Vol. 21, No. 5, 1987
Results and Discussion Nonlinear curves similar to those previously obtained with solid reagents (2, 5 ) were obtained when reflection absorbance values (a) were plotted against fixed ozone concentrations a t various exposure times (Figure 1)and (b) were plotted against fixed exposure times to various ozone concentrations (Figure 2). A smooth curve was also obtained when reflection absorbance values were plotted against the products of ozone concentration and exposure time. For the nearly linear portion of this curve, a sensitivity of 44.2 ppm min (unit reflection absorbance value)-l was obtained (Figure 3). A nearly rectilinear relationship was observed when reflection absorbance values were plotted against the square roots of the products of ozone
Environ. Sei. Technol. 1987, 27, 505-508
concentration and exposure time (Figure 4). The infrared spectra for the unexposed reagent and the reaction product with ozone were identical. The mass spectra showed the parent peak and fragmentation pattern in the reaction product to be identical with those of the unreacted reagent. The 400-mHz NMR spectra of the unreacted and reacted reagent in deuteriated chloroform showed significant peak broadening in the latter, which indicated the presence of unpaired electrons. The ESR spectrum of the product gave decisive evidence for the presence of a stable free radical. On the basis of the data obtained, a one-electron oxidation process is proposed:
The solid reagent is intended for use in passive monitoring or warning devices by means of visual Comparison to prepared color standards. The stability on storage, the sensitivity and selectivity of the reagent, and the color stability of the reaction product make phenoxazine an ideal reagent for this type of analysis. The fact that no humectant is required is another advantage. The very stable color produced is unusual for a free radical. Such color stability would permit long-term determinations of very low ozone concentrations. Registry No. Os, 10028-15-6; phenoxazine, 135-67-1.
Literature Cited (1) Lambert, J. L.; Beyad, M. H.; Paukstelis, J. V.; Chiang, Y. C. Anal. Lett. 1981, 14, 663. (2) Lambert, J. L.; Beyad, M. H.; Paukstelis, J. V.; Chejlava, M. J.; Chiang, Y. C. Anal. Chem. 1982,54, 1227. (3) Lambert, J. L.; Trump, E. L.; Paukstelis, J. V. Environ. Sci. Technol., first of three notes in this issue. (4) Environmental Protection Agency Fed. Regist. 1971,36(84),
1
The reaction is not sensitive to the relative humiditv of the airstream, and the red-orange color Produced bY"nitrogen dioxide is visually quite distinct from the dull brown color of the ozone reaction product.
Dependence of /[ 0,-O('D)]
8196. (5) Lambert, J. L.; Paukstelis, J. V.; Liaw, Y.-L.; Chiang, Y. C. Anal. Lett. 1984, 17, 1987. Received for review March 10,1986. Accepted December 19,1986. This research was suupported in part by National Science Foundation Grant CHE-8311011.
on the Choice of Extraterrestrial Solar Irradiance Data
John A. Rltter" Atmospheric Sciences Division, NASA Langley Research Center, Hampton, Virginia
23665
Donald H. Stedman Chemistry Department, University of Denver, Denver, Colorado 80208
Russell R. Dlckerson Meteorology Department, University of Maryland, College Park, Maryland
20742
Thomas E. Blackburn NASA Ames Research Center, Moffett Field, California
94035
Estimates of the photolysis frequency G) of tropospheric ozone (0,) to the excited singlet oxygen atom [O(lD)] depend on a knowledge of the extraterrestrial solar irradiance in the wavelength region between 300 and 320 nm. A standard format is proposed that facilitates the intercomparison of solar irradiance data sets in the 300-320-nm wavelength region so as to determine their appropriateness for use in calculating tropospheric values for j[O,-O(lD)]. Twelve data sets are thus compared, the results of which indicate that, with the exception of two data sets, the resulting j values are consistent with each other to within the accuracy of the measured data and thus are appropriate for use in determining j values. Computed j values from all 12 data sets are tabulated and indicate in a relative sense the dependence of modeled j values on the choice of the solar irradiance data set used.
Introduction A critical parameter in the modeling of photochemical processes in the troposphere on either the urban or global scale is the photolysis of 03: 0013-936X/87/0921-0505$01.50/0
Although most of the O(lD) atoms that are then produced are quenched to the ground state of O(3P) by nitrogen or oxygen, a significant quantity is still available for reaction with water to form hydroxyl radicals: O(lD) H 2 0 20H (2)
+
-
Hydroxyl radicals have been shown to be important not only in the removal of several trace gases including CO, CH,, C2Hs,Hz, HzS, and SO2(1) but also in the formation of ozone (2) leading to photochemical smog. Therefore, due to the central role that the presence of O(lD) atoms has in controlling photochemical processes on several scales in the troposphere, an understanding of the uncertainties inherent in the calculation of j[O,-O(lD)] is essential. The photolysis frequency 0')of any atmospheric molecule to a particular product channel is the integral of the product of solar actinic flux (I), absorption cross section (g),and quantum yield (4) to that channel. Thus, for the molecular species i, wavelength A, altitude z , temperature T, and zenith angle 8
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