Anal. Chem. 1982, 54,315-318
Table VI. Organophosphorus Insecticides Identified in Residential Indoor Air
insecticide
range of air concn, pg/m3
dichlorvos ronnel chloropyrifos diazinon malathion
0.05-28 0.01-10 0.01-7.0 0.01-2.0 0.10-1.0
inside kitchen cabinets to control crawling insects (crack and crevice treatment). Sampling in a number of homes under such treatment has revealed the presence of several insecticides in the air (Table VI). Typical levels encountered range from 0.01 to 5 pg/m3. In one instance, however, dichlorvos was found at 28 pg/m3 and chlorpyrifos at 7 pg/m3 3 days after treatment, as a result of over-application of these pesticides. The growing popularity of "build-it-yourself"log homes has created another potential indoor air contamination problem. Pentachlorophenol (PCP) has been commonly used to treat the logs used for construction, and since the bare surfaces of these logs usually comprise the inside walls, PCP vapors may readily enter the indoor atmosphere. In one such home, which was about 6 years old, air concentrations of 0.3-2 ~ g / m PCP ~ were found. The residents exhibited urinary PCP levels of 132 and 316 ng/g, which were much higher than those observed in the general population (9). PCBs are found ubiquitously in the indoor air, particularly in kitchens. PCB levels found in private dwellings by this laboratory have been in the 0.1-0.5 pg/m3 range as opposed to an average of 4 ng/m3 in the surrounding outdoor air (10). This laboratory has recently begun a national survey to assess the ubiquity of pesticides and other semivolatile organic chemicals in dornicillary air (11). Homes were selected in both industrialized urban and rural areas for study. Calibrated, preset pumps and sampling cartridges are sent by mail to the residents, along with instructions for collection and return of the samples. A questionnaire concerning the use of chemicals in and around the house, the type of construction, and air ventilation systems was developed. The survey has proceeded very smoothly over the first 6 months, with no problems attendant to shipment, handling, or collection of the samples. Use of the system for personal respiratory exposure assessment has also been proven in the field. This laboratory
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successfully employed the sampler on workers to monitor breathing zone air during cleanup of a PCB spill (12). Davis (13)has also applied the sampler to assess respiratory exposure of agricultural workers applying phosalone in apple orchards and homeowners using 2,4-D for lawn and garden weed control. ACKNOWLEDGMENT The authors thank William Barnard of the Environmental Monitoring Systems Laboratory, EPA, Research Triangle, NC, who conducted flow audits on the samplers. We also acknowledge Randy Barbee of our laboratory for his valuable technical assistance. LITERATURE CITED Lewis, R. G.; Lee, R. E., Jr. I n "Air Pollution from Pesticides and Agricultural Processes"; Lee, R. E., Jr., Ed., CRC Press: Cleveland, OH, 1976; Chapter 2. Giam, C. S.; Chan, H. S.; Neff, G. S. Anal. Chem. 1975, 47, 23 19-2320. Zimmerii, B. Chem. Rundsh. 1977, 30, 8-11. Budiansky, S. Envifon. Sci. Techno/. 1980, 14, 1023-1027. Interagency Research Group on Air Quality, "Workshop on Indoor Air Quality Research Needs"; Leesburg, VA, Dec 3-5, 1980. Lewis. R. G.: Brown. A. R.: Jackson. M. D. Anal. Chem. 1977. 49. 1668-1672. Edgerton, T. R.; Moseman, R. F. J. Chromafogr. Sci. 1980, 18, 25-29. Harris, D. E.; Hail, R. C. J. Chromafogr. 1979, 169, 245-259. Edgerton, T. R.; Moseman, R. F.; Lores, E. M.; Wright, L. H. Anal. Chem. 1980, 52, 1774-1777. MacLecd, K. E. Environ. Sci. Techno/. 1981, 15, 926-928. MacLecd, K. E.; Lewis, R. G. "Abstracts of Papers", 181.9 National Meeting of the American Chemical Society, Atlanta, GA, April 1981; American Chemical Society: Washington, DC, 1981; PEST 32. Lewis, R. G.; MacLeod, K. E.; Jackson, M. D. Chemical Congress of the American Chemical Society and the Chemical Society of Japan, Honolulu, HI, April 1979; American Chemical Society: Washington, DC, 1979; PEST 65. Davis, J. E. "Procedures for Dermal and Inhalation Studies to Assess Occupational Exposure to Pesticides"; USDA-EPA-Rutgers University Conference on Determination and Assessment of Pesticide Exposure, Hershey, PA, Oct 1980.
RECEIVED for review August 24,1981. Accepted November 9, 1981. This paper was presented in part at the Chemical Congress of the American Chemical Society and the Chemical Society of Japan, Honolulu, HI, April 1979, Paper No. 65 in the Pesticide Chemistry Division. It has been reviewed by the Health Effects Research Laboratory, U. S. Environmental Protection Agency, and approved for publication. Metion of trade names or commercial products does not constitute endorsement or recommendation for use.
CORRESPONDENCE Fluorescence Line Narrowing Spectrometry of Amino Polycyclic Aromatic Hydrocarbons in an Acidified Organic Glass Sir: Recently it has been shown (1-3) that laser excited fluorescence line narrowing spectrometry (FLNS) in organic glasses is a promising approach for the high-resolution analysis of polycyclic aromatic hydrocarbons (PAHs) in real samples. High resolution is defined here as the ability to distinguish between substitutional isomers of a PAH. Organic glasses were chosen as host media because their excellent optical quality minimizes laser light scatter (2) and allows for absolute quantitation (1). In addition, well-behaved glasses exist which are excellent solvents for both polar and nonpolar compounds. 0003-2700/82/0354-0315$01.25/0
A particular advantage of the glasses employed in ref 1-3 is that they contain water and one has hope, therefore, that contaminated water samples can be directly analyzed. Application of FLNS in such glasses to the polar derivatives of PAHs in, for example, shale oil wastewater would be very interesting. One difficulty associated with polar PAHs is that there is a dearth of good high-resolution optical data available for them. Thus, the electronic and vibrational properties of their lower lying electronic states, including the fluorescent state (SI), are not well understood. This is particularly so for 0 1982 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
the amino derivatives of PAHs (amino-PAHs) which we have chosen to study because of their carcinogenic properties. Even the room temperature solution absorption spectra of aminoPAHs portend another difficulty; namely, that their S1states may possess significant charge-transfer (CT) character due to the strong mesomeric effect (4) of the -NH2 group. The spectra of these compounds are characterized by a lowest energy absorption system that is diffuse relative to that of the parent. This type of absorption, especially when followed by a structured higher energy system, is characteristic of a CT state. It is well-known from studies on intermolecular CT complexes that it is generally not possible to observe a quasi-line fluorescence spectrum from a state possessing significant CT character (5-8) due to the strong linear electron-phonon coupling which produces intense phonon side band activity. Concomitantly, the zero-phonon vibronic transitions are essentially Franck-Condon forbidden. There is no reason to expect that the linear electron-phonon coupling associated with intramolecular CT states should be weaker. In this paper dealing with amino-PAHs three questions are addressed: Can the diffuse SI absorption system of these compounds be associated with an excited state possessing significant CT character? Do their S1 states give rise to FLN? If FLN is not characteristic of these states, can modification of water containing glasses modify the S1states to an extent which makes FLN possible?
EXPERIMENTAL SECTION Instrumentation. The instrumentation for FLNs has been described in detail elsewhere (2). Glasses. Three organic glasses were employed for our investigations: 80% (5:4 glycerokwater) + 20% ethanol; 5:4 glycerokHC1,2 N; 75% (1:lmethylcyclohexane:2-methylpentane) + 25% cyclohexane. The cells used for the first two were polystyrene culture tubes manufactured by Falcon (Oxnard, CA). Transparent polycarbonate cylindrical tubes (Nalge Co., Rochester, NY) were employed for the latter two glasses due to their inertness. All solvents were obtained from commercial sources (laboratory reagent grade) and used without further purification. Fluorescence measurements were run on all glass solvents to ensure that impurity emission was not interfering in the spectral regions of interest. 1-and 2-Aminoanthraceneand 1-aminopyrene were obtained from Aldrich Chemical Co. and purified by vacuum sublimation prior to their use. Experiments with sublimed samples were performed on freshly prepared solutions since the above NH2-PAHsdecompose over time. Other details concerning sample preparation can be found elsewhere (9). RESULTS AND DISCUSSION 1-Aminopyrene. The room-temperature absorption spectra of 1-aminopyrene in both the glycerol/water/ethanol solvent and the pentane/ 2-methylpentane/methylcyclohexane solvent are similar although somewhat better resolved in the latter. The latter spectrum is essentially identical with the spectrum reported by VaEk et al. (10)with the origin of the first system (S,) near 395 nm and that of the second system near 350 nm. A discussion of state assignments is contained in this reference. In the glycerol/HC1(2 N) solvent however, the origin of the first system is a t -374 nm and the first two absorption systems closely resemble those of the parent pyrene (9). In the acidified glass the vibrational structure is significantly better resolved due to protonation of the amine eliminating interaction of the -NH2 lone pair electrons with the n-electron system. No FLN was observed for 1-aminopyrene in either the glgcerol/water/ethanol or the pentane/2-methylpentane/ methylcyclohexane glasses excited at several different wavelengths in the vicinity of the S1 origin near 390 nm. Only an extremely broad fluorescence extending from -390 nm to -460 nm with a broad shoulder near 400 nm and more intense
G x 10-3 (cm-11 7 0
27.5
25i0
2;1.5
26;5
I-AMINOPYRENE 3ppm IN H C I ILNI-GLYCEROL GLASS
X
exc=374.4 nm
Flgure 1. Fluorescence line narrowed spectrum of 1-aminopyrene (3 ppm) In the glyceroVHCI (2 N) glass, 4.2 K; X(excitation) = 374.4 nm; cf. text.
V X 23.5
I(crn-11
I 24.5
24.0
25.0 I
26.0 I
25.5 I
2 - A M I NOANTRHACENE IO ppm I N HCI I2N)-GLYCEROL GLASS
A
I 420
I
1
e x c = 382.5nm
I
I
4 10
400
X
I
I
I
390
(nm)
Flgure 2. Fluorescence line narrowed spectrum of 2-aminoanthracene (10 ppm) in the glyceroVHCI (2 N) glass, 4.2 K; h(excitatlon) = 382.5 nm. The Intense feature near 382.5 nm is due to laser light scatter. The first zero-phonon vibronic band is at -388 nm.
maximum near 420 nm was seen (9). The spectra did not shift with excitation wavelength. This type of spectra is typical of a CT state. For the glycerol/HCl (2 N) glass, excitation at 374.4 nm into the origin band of the S1 absorption system yielded FLN, Figure 1. In this figure the peak labeled with L is the fluorescence origin contaminated, however, with scattered laser light. Sharp features to lower energy of L correspond to zero-phonon vibronic transitions (beginning with the 402, 430 cm-l doublet near 380 nm). The vibrational intensities and frequencies are, as expected, quite similar to those of pyrene (9). The vibrational analysis of the spectrum in Figure 2 can be found in ref 9. The spectrum provides a nice example of the selectivity afforded by FLN especially when it is noted that it was obtained with a spectrometer band-pass of -10 cm-l. 2-Aminoanthracene. As in the case of 1-aminopyrene, the room temperature absorption spectra of 2-aminoanthracene
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ANALYTICAL CHEMISTRY, VOL. 54, NO. 2, FEBRUARY 1982
v x 2?,5
10-3 1 c m - l )
27.0
2].01
251.5
I -AMINOANTHRACENE IOppm I N HCI I Z N b G L Y C E R O L GLASS e x c = 384.5 nm
L I 410
I
I
I
400
I
390
X
(om)
Figure 3. Fluorescence line narrowed spectrum of laminoanthracene (10 ppm) in the glyceroi/HCi (2 N) glass 4.2 K; X(excitation) = 384.5 nm. The first zero-phonon vibronic band is at -390 nm. The intense signal to higher energy of it is due to laser light scatter.
in the neutral glasses are diffuse with a very broad low-energy absorption peaked near 400 nm. With excitation coincident with the diffuse absorption band, no FLN was seen for 2aminoanthracene in these glasses, only a broad CT-like fluorescence onsetting at -400 nm and peaking near 450 nm (9). In contrast, the absorption spectrum of 2-aminoanthracene in glycerol/HC1(2 N) is devoid of the very broad low energy system showing instead a single structured system (9),very much like that of anthracene, and having a resolved origin band at -380 nm. Excitation into the origin and 380 cm-l vibrational bands yielded FLN (9). An example is shown in Figure 2 for X(excitati0n) = 382.5 nm. The sharp zero-phonon feature a t 388 nm corresponds to a 381-cm-l ground-state vibration. The other sharp features to lower energy correspond to higher frequency fundamentals (9). On the basis of vibrational frequencies and intensities, the spectrum in Figure 2 is similar to the FLN spectrum of anthracene and its methyl derivatives (2, 11). 1-Aminoanthracene. The room-temperature absorption spectrum of 1-aminoanthracenein glycerol/water/ethanol also shows a broad CT-like absorption maximizing at 400 nm (9, 12). In glycerol/HCl (2 N) the spectrum (9) is virtually identical with that of 2-aminoanthracene so that one recovers the absorption spectrum of anthracene due to its short axis polarized S1 state at 380 nm (13). Excitation into the broad lower energy band of l-aminoanthracene in the glycerol/water/ethanol glass yielded no FLN, only a broad CT-like spectrum onsetting near 410 nm with a single maximum at -460 nm (9). However, FLN was observed for the glycerol/HC1(2 N) glass for excitation into the origin and 400-cm-' vibrational bands of the lowest absorption system (9). Figure 3 is a FLN spectrum for excitation into the origin with X(excitation) = 384.5 nm. The sharp zero-phonon line a t 390 nm corresponds to a 396-cm-l ground-state vibrational fundamental. The three prominent lower energy zero phonon bands correspond to fundamentals with frequencies 1289,1435, and 1588 cm-l. The analogue of
317
the 396-cm-l vibration for 2-aminoanthracene has a frequency of 381 cm-l so it is clear that with this difference and with the 2.0-nm shift in excitation wavelength FLN can be used to distinguish between 1- and 2-aminoanthracene. T h e Origin o f D i f f u s e n e s s of t h e L o w e s t A b s o r p t i o n System. It is well established that FLN with PAHs is generally achievable. This is a consequence of the fact that the fluorescent a7r* states of these species do not strongly couple to the lattice modes of the host medium. Besides the amino-PAHs discussed in this paper, others (IO, 14) exhibit a lowest energy absorption system which is diffuse relative to the SIabsorption system of the parent. Substituents which are less mesomeric do not have this effect (IO, 12,14). The diffuse absorption coupled with the observation that excitation into the appropriate regions of the SI absorption system produces no FLN, only a very diffuse emission, indicates that the SI state possesses significant CT character. This character could derive from a one-electron CT excitation involving the lone pair of the -NH2 (approximately coplanar configuration with the parent ring system) and a* MOs. Unfortunately only semiemperical MO calculations have been performed on the amino-PAHs discussed here (10,12). Higher level (ab initio) calculations are required for accurate assessment of the involvement of the -NH2 group in the a-electron network of the parent. Dual F l u o r e s c e n c e o f 1- and 2 - A m i n o a n t h r a c e n e . A surprising observation was that both aminoanthracenes in the glycerol/water/ethanol glass exhibit a dual fluorescence. In addition to the CT-like fluorescence already mentioned, excitation close to the onset of the second absorption system produced intense FLN spectra (9) which in vibrational intensities and frequencies are very similar to the spectra shown in Figures 2 and 3. Dual fluorescence was not observed for 1-aminopyrene. The higher energy component of the dual fluorescence has three important characteristics: it originates from the state being excited; it exhibits FLN and; it is similar to the fluorescence spectrum of anthracene associated with its 380-nm S1 state. The lower energy component obtained by exciting into the diffuse lowest energy absorption system is exceedingly broad and exhibits a Stoke's shift of -4000 cm-l (9). Stoke's shifts of this magnitude are characteristic of CT states (5-8). We note that the low and higher energy onsets of absorption and fluorescence, respectively, overlap. We have no evidence that the CT-like fluorescence is from a state other than the one being excited (as has been suggested for p cyanodimethylaniline (15). Thus, the intense dual fluorescence most likely represents a notable exception to Kasha's rule or is due to two different species. The fact that the intensity of the higher energy sharp fluorescence system is high makes the first possibility difficult t o reconcile in light of the current understanding of radiationless processes. With regard to the second possibility, the fact that purification (sublimation) did not alter the absorption spectra of 1- and 2-aminoanthracene nor their fluorescence behavior argue against one component of the fluorescence being due to an impurity. One possibility we intend to explore is that the two species are different rotamers of the aminoPAH. One would expect, however, that similar rotamers could exist in 1-aminopyrene, for which dual fluorescence was not observed. Finally we emphasize that the lack of dual fluorescence for 1-aminopyrene underscores another advantage of utilizing water-containing glasses in FLN spectrometry; namely, that FLN was observed only in the acidified glass. ACKNOWLEDGMENT The assistance of M. McGlade during the course of the experiments is gratefully acknowledged.
318
Anal. Chem. 1982, 54, 318-320
LITERATURE CITED (1) Brown, J. C.; Edelson, M. C.; Small, G. J. Anal. Chem. 1978, 50, 1394. (2) Brown, J. C.; Duncanson, J. A., Jr.; Small, G. J. Anal. Chem. 1980, 5 2 , 1711. (3) Brown, J. C.; Hayes, J. M.; Small, G. J. I n “Lasers and Chemlcal Analysis”; Hieftje, G. M., Lytle, F. E., Travis, J. C., Eds.; Humana Press: Cllfton, NJ, 1981. (4) Murrell, J. N. ”The Theory of the Electronic Spectra of Organlc Molecules”; Wlley: New York, 1963. (5) Haarer, D. Chem. Phys. Lett. 1974, 2 7 , 91. (6) Beckman, R. L.; Hayes, J. M.; Small, G. J. Chem. Phys. 1977, 21, 135. (7) Beckman, R. L.; Small, G. J. Chem. Phys. 1978, 3 0 , 19. (8) Haarer, D. J . Chem. Phys. 1977, 6 7 , 4076. (9) Chlang, I.Masters Thesls, Iowa State Unlverslty, 1981. (10) VaGk, M.; Whlppie, M. R.; Berg, R.; Mlchl, J. J . Am. Chem. SOC. 1978, 100, 6872. (11) Brown, J. C. Ph.D. Dlssertatlon, Iowa State Unlverslty, 1981. (12) Steiner, P. R.; Michl, J. J . Am. Chem. SOC.1978, 100, 6861. (13) SMman, J. J . Chem. Phys. 1958, 2 5 , 115. (14) Whlpple, M. R.; VaGk, M.; Michl, J. J . Am. Chem. SOC.1978, 100, 6844.
115) Grabowskl, 2 . R.; Rotklewlcz, K.; Siemlarczuk, A,; Cowley, D. J.; Braumann, W. Nouv. J . De Chlm. 1979, 3, 443.
Ames Laboratory-USDOE Chemistry Iowa State University Ames, Iowa 50011
Iris Chiang J o h n M. Hayes Gerald J. Small* and Department of
RE~EXVFDfor review September 18,1981. Accepted November 3,1981. Ames Laboratory is operated for the U.S. Department of Energy by Iowa State University under Contract No. W-7405-Eng-82. This research was supported by the Assistant Secretary for Environment, Office of Health and Environmental Research. I.C. would like to thank the Venezuelan FGMA for a graduate fellowship.
On-Line Chemiluminescence Detector for Hydrogen Sulfide and Methyl Mercaptan Sir: The need for continuous monitoring of species like H2S and CH3SH in the atmosphere is obvious because of their toxic nature and is particularly important in synfuel production and geothermal energy utilization. Also, H2S is an impurity in synthesis gas (H, and CO) which is used in the industrial production of methanol, methane, glycols, and other hydrocarbons. Costly catalysts are readily “poisoned” unless the H2S level is kept below 1ppm (1). Presently, HzS in air can be determined by colorimetry (2),conversion to metal sulfides and subsequent photometry (31, gas chromatography with flame photometric detector (41, and ion-selective electrodes (5). For low concentration levels, all of these techniques require collecting the gas sample of interest over fairly long times and/or some chemical preparation. Truly continuous monitoring is therefore not achieved. Chemiluminescence under the right conditions is an extremely sensitive method, with the possibility of obtaining one photon for each molecule of interest. The most widely used reagent in the gas phase is ozone (atomic oxygen). Unfortunately, the reaction is not very selective, and compounds like SOz, nitrogen oxides, and unsaturated hydrocarbons all produce emission that can interfere with the detection of HzS (6,7).It is apparent that a selective detector should be based on emission from a species related chemically to the analyte rather than the reagent. ClO, is an interesting reagent in that it reacts, vide infra, with H2S and CH3SH to produce sulfur atoms, which recombine to form electronically excited Sz and in turn result in fluorescence. This specificity is then the key of this work. Chemiluminescence resulting from the reaction between CIOz and reduced forms of sulfur at elevated temperatures (8) has been alluded to. However, we are not aware of any confirmation or any other observations, especially at room temperature or in a flow system. This is probably due to the large quenching cross-sections of the excited state of Sz (9) and the high reaction order involved (two H2S per S2 molecule). Observation at room temperature is desirable because the background radiation from the flame (8) is eliminated. To minimize the effects of quenching, one must keep the reaction zone at reduced pressures. To maximize sensitivity despite the high-order reaction, one must keep the volume of the reaction zone small, and the reagent gas (CIOz) must 0003-2700/82/0354-0318$01.25/0
be in excess to produce complete reaction in a pseudo-firstorder regime. A successful on-line chemiluminescence detector is therefore dependent on meeting these various design parameters and is reported here. EXPERIMENTAL SECTION To maintain a constant reduced pressure of Pzin a reaction zone while sampling at atmospheric pressure Pl,one simply needs two pinholes with effective apertures of ul and u2 in area to separate the regions between Pl/Pzand P,/P3,respectively, where P3 is an evacuated zone after P2 Relating the conductance through each region, one has (pl - PZkl = (PZ- P3)aZ (1) If P3 is essentially the residue pressure of the pumping system, it can be neglected relative to Pz, so that Pzcan be maintained at a well-determined value independent of possible fluctuations in P3. Such a cell design is shown in Figure 1. The inlet tubes (E) are 1 mm i.d. quartz tubings aligned with the ends 0.5 mm apart. A sheath (D) based on a 3 mm i.d., 60 mm long quartz tube is used to define the reaction zone, providing a volume of 16 mm3. The aperture for flow, u2, has an area given by the difference in cross-sectionalareas of the outside of E and the inside of D and is 0.070 mm2. The use of quartz allows chemiluminescence below 320 nm to be observed through a in. thick window (F). A mechanical pump (Duo Seal, Welch, Chicago, IL) provides the flow and is connected to the cell via B after a cryogenic trap. The cell body (A) is machined out of brass locally and is lined with aluminum foil opposite the window (F) to enhance the collection of light. The reacting gases are introduced into the cell through metering valves attached at C. A fine metering valve (Nupro, Willoughby, OH, type “S”)packed with Teflon is used for CIOz and a stainless steel leak valve (Veeco, Plainview, NY, VVB-50s) is used for the air-HzS mixtures. The effective aperture areas for the two at typical operating conditions mm2 and 9 X mm2, respectively. One then are 1.6 X determines the pressure in the reaction region, Pz,to be about 30 torr. A 56 DUVP photomultiplier tube (Amperex, Hicksville, NY) is attached directly to the window F to provide a collection efficiency of about f / l . Photon counts are registered by use of an Ortec (EG&G,Oakridge, TN) 9315 photon counter and a 9325 amplifier-discriminator. Spectral scans are obtained through a grating monochromator (McPhenon, Acton, MA, Model 270) after passing through a lens system again with an f / l collection efficiency. 0 1982 American Chemical Soclety
