Envlron. Sci. Technol. 1987, 21, 497-500
M. Atmos. Environ. 1987,21, 457-461. (9) Eudy, L. W.; Thome, F. A.; Heavnre D. L.; Green, C. R.; Ingebrethson, B. J. Presented at the 39th Tobacco Chemists’ Research Conference, Montreal, Canada, Oct. 1985. (10) Eatough, D. J.; Benner, C.; Mooney, R. L.; Bartholomew, D.; Steiner, D. S.; Hansen, L. D.; Lamb, J. D.; Lewis, E. A.; Eatough, N. L. Abstracts of Papers, 19th Annual Meeting of the Air Pollution Control Association, Minneapolis, MN, June 1986; Air Pollution Control Association: Pittsburgh, PA, 1986; paper 86-68.5. (11) Palmes, E. D.; Burton, R. M.; Ravishankar, K.; Solomon, J. J. Am. Znd. Hyg. Assoc. J. 1986, 47, 418-420.
Literature Cited (1) Repace, J. L.; Lowrey, A. H. Science (Washington, D.C.) 1980,208, 464-472. (2) Spengler, J. D.; Treitman, R. D.; Tosteson, T. D.; Mage, D. T.; Soczek, M. L. Environ. Sci. Technol. 1985, 19, 700-707. (3) Weber, A,; Fischer, T. Znt. Arch. Occup. Environ. Health 1980,47, 209-221. (4) Repace, J. L.; Lowrey, A. H. Environ. Int. 1985,11, 3-22. (5) Sebben, J.; Pimm, P.; Shephard, R. J. Arch. Enuiron. Health 1977, 32, 53-58. (6) Badre, R.; Guillerme, R.; Abram, N.; Bourdin, M.; Dumas, C. Ann. Pharm. Fr. 1978,36,443-452. (7) Brunnemann, K. D.; Hoffmann, D. ZARC Sci. Publ. 1978, 19, 343-356. (8) Hammond, S. K.; Leaderer, B. P.; Roche, A. C.; Schenker,
Received for review September 23,1986. Accepted January 12, 1987.
I-Methylperimidine as a Solid Monitoring Reagent for Nitrogen Dioxidet Jack L. Lambert,” Eric L. Trump, and Joseph V. Pauksteils Department of Chemistry, Kansas State University, Manhattan, Kansas 66506
1-Methylperimidine on a solid support such as filter paper, with calcium chloride ag a humectant, serves as a stable, sensitive, and selective monitoring reagent for nitrogen dioxide in air. The reagent is intended for use with visual color comparison standards relating response of the reagent to concentration of nitrogen dioxide with constant time of exposure. Studies were made of the reagent response to concentration at constant exposure time and to time of exposure at constant concentration. The effects of relative humidity in the reagent storage container and in the test atmospheres were investigated. No interference was observed from ozone, chlorine, bromine, hydrogen sulfide, sulfur dioxide, carbon monoxide, or carbon dioxide.
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Introduction
Following the development of a solid, dry tin(I1)-diphenylcarbazide reagent responsive to both ozone and nitrogen dioxide (1,2),the strong oxidants of concern as atmospheric pollutants, studies were made to prepare new reagents specific for each of these oxidants. A number of lJ8-diaminonaphthalene derivatives were synthesized following an observation that Proton Sponge, l&bis(dimethy1amino)naphthalene(Aldrich),produced a color with small concentrations of nitrogen dioxide. This compound, however, did not respond to nitrogen dioxide once it was protonated, which would severely limit its usefulness. 1,8-Diaminonaphthalene reacted readily with nitrogen dioxide but it is too subject to oxidation by atmospheric oxygen to be of use as a reagent. This study involved the synthesis and reactions of perimidine and five of its derivatives prepared by methods (or modifications thereof) described in the literature and quantitative studies of the reaction of 1-methylperimidine with nitrogen dioxide. Experimental Section
Table I summarizes the solubility characteristics and color responses to nitrogen dioxide of perimidine and the five derivatives synthesized. On the basis of these observations, l-methyl-2-(dimethylamino)perimidineand 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/87/0921-0497$01.50/0
2-phenylperimidine were eliminated from further consideration because visual detection of the color changes were difficult. Perimidine was eliminated because of its gradual darkening over a period of a few hours exposure to air. 1-Acetylperimidine was eliminated because its color response was considerably less sensitive than those of 1methyl- and 2-methylperimidine. 2-Methylperimidinewas eliminated from consideration after the humectant (calcium chloride) was found to discolor the compound and destroy its reactivity. Only 1-methylperimidine was unaffected by atmospheric oxygen and the presence of the humectant, had the desired degree of sensitivity for nitrogen dioxide, and did not react with ozone. Preparation of 1-Methylperimidine (Scheme I). 1,B-Diaminonaphthalene(Aldrich) was obtained as a discolored product and was purified by one or more recrystallizations from a 1:l water-ethanol mixture. Further decolorization, if needed, was accomplished by heating an ethanol solution of the compound with a small amount of decolorizing carbon and filtering before another recrystallization step. The white product should be used immediately. Brown and Evans (3) suggested refluxing l,t)-diaminonaphthalene with formamidine acetate in ethanol but gave no details. The procedure worked out in this laboratory was to dissolve 15.8 g (0.100 mol) of recently purified 1,B-diaminonaphthalene in 400 mL of ethanol in a 1-L round-bottom flask, add 12.0 g (0.115 mol) of formamidine
0 1987 American Chemlcal SocietY
Environ. Sci. Technol., Vol. 21, No. 5, 1987 497
Table I. Response of Perimidine Derivatives to Nitrogen Dioxide
color after exposure compounds perimidine derivatives 1-methyl 2-methyl l-methyl-2-(dimethylamino) 1-acetyl 2-phenyl
solvent ethanol
before exposure pale yellow
ethanol HzO (hot) DMF DMF nonea
pale yellow pale yellow green pale yellow brown
red
wet
dry orange
red red greenish brown red brown
orange orange greenish brown orange brown
Compound insoluble in all common solvents.
acetate (Aldrich), and reflux the mixture for at least 4 h. The reaction should be carried out in a fume hood, as ammonia gas is evolved. Any formamidine acetate that is undissolved prior to refluxing will dissolve upon heating. Perimidine was obtained in 80% yield as light yellow needles on recrystallization from 95 % ethanol. Dry glassware and dry tetrahydrofuran (THF) are required for the synthesis of 1-methylperimidine. The tetrahydrofuran was dried over Drierite, filtered, and treated with several small pieces of sodium metal that had been stored under nitgrogen rather than oil. Sodium hydride, 0.48 g, obtained commercially as a 97% dry solid from Aldrich, was added to 200 mL of THF in which 1.68 g (0.01 mol) of perimidine had been dissolved, followed by 1.43 g (0.01 mol) of methyl iodide. Although a stoichiometric amount of methyl iodide was used, a small amount of a water-soluble red substance was formed-possibly a quaternary ammonium salt. After reaction, the THF solvent was removed by distillation at atmospheric pressure. A Soxhlet extraction was performed on the solid residue with diethyl ether as the solvent. The byproduds sodium iodide and the small amount of quaternary ammonium salt were insoluble and not extracted. The product l-methylperimidine was isolated by evaporation of the ether in 30-4070 yield, calculated on the basis of perimidine as the starting material. It is yellow and very similar in appearance to perimidine. Comparison of the mass spectra of the parent perimidine and the prepared l-methylperimidine indicated that the desired methylation had taken place and that the product was pure. The melting point is above 300 "C. Reagent Papers. A 0.02 M solution of l-methylperimidine was prepared by dissolving 0.364 g of the purified product in 100 mL of 95% ethanol. This solution was added to 100 mL of an aqueous 2% (wt/vol.) solution of calcium chloride, CaC1, (Fisher), weighed as the anhydrous salt. Whatman No. 1 filter papers, 4.25 cm diameter circles, were soaked in the reagent solution for 15 min, oven-dried at 70 "C for several hours, and stored in a desiccator. Exposure Vessel. The exposure vessel, a modified inverted Kimble low-form cap-style weighing bottle with 55-mm i.d., had inlet and outlet ports as described by Lambert et al. (2). Gas Dilution System. Sealed poly(tetrafluoroethy1ene) tubing (1/4-in.,o.d.,1/32 in. thick wall) containing liquid nitrogen dioxide was prepared in several lengths and used as permeation tubes. The tubes were calibrated for permeation rate of nitrogen dioxide by measurement of weight loss vs. time. By use of various lengths of permeation tubes and various flow rates of the diluent airstream, desired concentrations of nitrogen dioxide were produced. The sample determinations were made at 25 "C and 50% relative humidity, except for the studies on the effects of 498
Environ. Sci. Technol., Vol. 21, No. 5, 1987
relative humidity on the reagent. Reflection Measurements. A Perkin-Elmer 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. Measurements for all the tests were made at 460 nm, which is the absorbance maximum for the reaction product and near the minimum absorbance for the reagent. Effects of Relative Humidity in the Airstream. To observe the effects of various conditions of relative humidity on the reagent papers, six airstreams were adjusted to equal flows within the precision of the flow meters. Each airstream was passed either through a drying tower or through a water bubbler. By this method, six different values of relative humidity in the airstream were obtained. Effects of Relative Humidity in the Storage Vessel. As described by Carr and Harris (6),saturated solutions of various salts were used to provide known conditions of relative humidity inside the reagent paper storage containers. After 10 days of storage, reagent papers thus stored were exposed to an airstream containing 0.315 ppm nitrogen dioxide at 50% relative humidity. Interference Tests. Reagent papers were exposed to approximately 1ppm ozone for long periods of time and to other atmospheric gases of concern at much higher concentrations. Identification of the Reaction Product of 1Methylperimidine. Qualitative organic tests were made on the reaction product of 1-methylperimidine and nitrogen dioxide to determine whether the product was a nitro or a nitroso derivative.
Results and Discussion 1-Methylperimidinereagent papers with calcium chloride as a humectant are essentially dry to the touch and can serve as passive monitoring or warning devices for nitrogen dioxide by color comparison to prepared standards. Nonlinear smooth response curves typical of those previously observed with solid reagents for other gaseous pollutants (2,4) were obtained when reflection absorbance values were plotted (a) against various concentrations of nitrogen dioxide for fixed exposure times (Figure 1)and (b) against various exposure times for fixed concentrations of nitrogen dioxide (Figure 2). The range of concentrations was 3.3-21.9 ppm, and the range of exposure times was 0.5-2.5 min. In actual practice, the preferred method probably would involve visual comparison of color intensities obtained at constant time of exposure to prepared permanent color standards. The smooth curves obtained
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Flgure 3. Effect of relative humidity inside the reagent paper storage vessels prior to exposure of the papers to nitrogen dioxide. The reagent papers were exposed after 10 days of storage for 3 min to 18.6 ppm of nitrogen dioxide at 50% relative humidity.
NO:,
concentration, ppm
Figure 1. Reagent response at 25 OC and 50% relative humidity to nitrogen dioxide at various exposure times. The average of five determinations at 460 nm, the range, and the standard deviation are shown for each set of conditions. Each curve represents a constant concentration of nitrogen dioxide. 0.5
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indicate an underlying uniformity of response by the reagent. The reagent papers are best stored dry, as the effects from storage under other conditions of relative humidity cause the response to vary, as shown in Figure 3. The
effect of relative humidity in the sample airstream is significant, but the data indicate that consistent results should be obtained if the relative humidity is between 30% and 70% (Figure 4). False low readings with the properly dried and stored reagent would be obtained only in very dry atmospheres. A series of color comparison standards relating reagent color responses to nitrogen dioxide concentrations at regular relative humidity intervals (e.g., each 10% variation) would be an added refinement when relative humidity values are known. No interference was observed from long exposure of the reagent papers to ozone at approximately 1 ppm nor to exposure to chlorine, bromine, hydrogen sulfide, sulfur Environ. Sci. Technol., Vol. 21, No. 5, 1987 499
Environ. Sci. Technol. 1987, 21, 500-503
dioxide, ammonia, carbon monoxide, and carbon dioxide at much higher concentrations. The reaction product of 1-methylperimidine with nitrogen dioxide (Scheme 11) most likely is either a nitro or nitroso derivative. When 1-methylperimidine alone was exposed to nitrogen dioxide, an orange compound was obtained, but with water present the product was a more intense red. Calcium chloride as a humectant provides water for the desired reaction of 1-methylperimidine. The orange product of dry 1-methylperimidine with nitrogen dioxide tested positive with Feigl’s test (5) for p-nitro aromatic amines, in which a small amount of sample was mixed with diphenylamine in a casserole and heating to melting. A blue color indicated the orange product to be 6- or 7-nitro-1-methylperimidine. When the red product obtained with moist reagent and nitrogen dioxide was treated with phenol and concentrated sulfuric acid (another test described by Feigl), a blue color confirmed the reaction product to be 6- or 7-nitroso-1-methylperimidine. 1-Methylperimidine, a tertiary aromatic amine, thus forms a nitroso derivative rather than the nitro derivative under the conditions in which very small quantities of nitrogen
dioxide are absorbed in the moisture provided by the humectant to form nitrous and nitric acids. Registry No. NO2, 10102-44-0; CaCl,, 10043-52-4; 1methylperimidine, 19585-93-4;1,8-diaminonaphthalene, 479-27-6; formamidine acetate, 3473-63-0; pyrimidine, 289-95-2.
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) Brown, D. J.; Evans, R. F. J. Chem. SOC.1962, 4093. (4) Lambert, J. L.; Paukstelis, J. V.; Liaw, Y.-L.; Chiang, Y . C . Anal. Lett. 1984, 17, 1987. (5) Feigl, F. Spot Tests in Organic Analysis; Elsevier: London, 1960. (6) Carr, D. S.; Harris, B. L. Znd. Eng. Chem. 1949,41, 2014.
Received for review March 10,1986. Revised manuscript received December 19,1986. Accepted January 22, 1987. This research was supported in part by National Science Foundation Grant CHE-8311012.
Palladium(11)-Acetamide Complex as a Solid Monitoring Reagent for Carbon Monoxidet Jack
L. Lambert,* Yun-Long Liaw, and Joseph V. Paukstelis
Department of Chemistry, Kansas State University, Manhattan, Kansas 66506
Yuan C. Chiang Department of Chemistry, Kansas Wesleyan University, Salina, Kansas 6740 1
A study of solid salts containing cationic complexes of palladium(I1) with neutral, weakly complexing ligands resulted in the discovery of the palladium(I1)-acetamide-tetrafluoroborate reagent, in which acetamide is present in 20-fold molar excess. It was found that a successful reagent of this type must have a ligand that complexes palladium(I1) weakly, but more strongly than does water, with water available for subsequent reaction. Carbon monoxide appears to coordinate with the palladium(I1)-acetamide complex, which then reacts with water to form, simultaneously, palladium(0) metal that is black, carbon dioxide, and hydrogen ion. The reagent is described as a visual warning device for the presence of carbon monoxide. Introduction
Chemical methods for carbon monoxide measurement carried out at room temperature rely on either palladium(11) or silver compounds, with the unique exception of hemoglobin. Silver(1) lightly complexed with p-sulfaminobenzoate anion in strongly alkaline solution (1) is reduced by carbon monoxide to a silver sol, the hue and absorbance of which vary with concentration. Palladium(11) salts in aqueous solution are reduced by carbon monoxide to black metallic palladium. A variant of this type of reaction involves complexing the unreacted palladium(I1) cation with excess iodide to form red tetraiodopalladate(I1) anion, which can be determined spec-
trophotometrically (2). Three colorimetric reactions for carbon monoxide that produce soluble colored compounds without free metallic palladium are the tetrachloropalladate~II)-(ethylenediaminetetraacetato)ferrate(III)1,lO-phenanthroline solution that produces red-orange tris(1,lO-phenanthroline)iron(II) cation ( 3 ) , the tetrachloropalladate(I1)-leucocrystal violet-iodate solution that produces crystal violet (4), and the tetrachloropalladate(11)-cacotheline solution that produces violet dihydrocacotheline (5). Solid reagents for carbon monoxide consist generally of moistened palladium(I1) salts on supports, which carbon monoxide reduces to black palladium metal, and palladium(I1) silicomolybdate or molybdate on silica gel, which carbon monoxide reduces to produce “molybdenum blue” (6-8). Yellow tetrasulfitopalladate(I1) complex anion on silica gel is reduced by carbon monoxide to produce a brown color (9). The purpose of this study (10) was to examine the nature of the palladium(I1)-carbon monoxide reaction and, if successful, to develop a solid reagent that would not require liquid water or a substance providing water, such as silica gel. The study provided some insights into the palladium(I1)-carbon monoxide reaction mechanism and produced a palladium(I1) reagent that may be used on supports such as paper. The reagent is dry to the touch but does contain water in the hygroscopic acetamide for a sequential reaction that produces dispersed black palladium metal. Experimental Section
+Thispaper was presented at the 190th National Meeting of the American Chemical Society,Chicago, IL, Sept. 8-13, 1985, as CHAS 11. 500
Environ. Sci. Technol., Vol. 21, No. 5, 1987
Preparation of Test Reagents. All of the compounds discussed here were prepared by displacement of acetonitrile ligand from tetrakis(acetonitrile)palladium(II)
0013-936X/87/0921-0500$01.50/0
0 1987 American Chemical Society
