Anal. ch8m. 1990, 62, 1055-1060 (43) Aivarer, F. J.; Parekh, N. J.; Matusquewski, 8.; Givens, R. S.; Higveh. T.; Schowen, R. L. J . Am. Chem. SOC. 1986, 708, 6435-6437. (44) Turro, N. J. Modern Molecular Photochemistty; Benjamin: New York, 1981; pp 362-392. (45) Brina, I?.;Bard, A. J. J . Electroanal. Chem. Interfacial Electrochem. 1987, 238, 277-295. (46) Landegren, U.;Kaiser, R.: Caskey. C. T.; Hood, L. Science 1988, 242,
1055
229-237. (47) Worthy, W. Chem. Eng. News 1989, 67(41), 21-23.
RECEIVED
for review November 3, 1989. Accepted February
5, 1990.
Isoprene Measurement by Ozone-Induced Chemiluminescence Alan J. Hills* and Patrick R. Zimmerman National Center for Atmospheric Research (NCAR), P.O. Box 3000, Boulder, Colorado 80307-3000
An instrument has been constructed that monitors gaseous Isoprene contlnuously. The basis for detection is chemliuminescence wlth ozone. The lsoprene/ozone reactlon produces electronically excited formaldehyde whose subsequent emission to the ground state is vlewed with a blue-sensitive photomuitlplier tube. The instrument has a response time of 0.1 8, Is llnear over 3 orders of magnitude, and has a detectlon limit for isoprene of 400 pptv (at S I N = 2 and 5-s eiectronic thne constant). Seiectivltles over various alkenes and other compounds are presented. The first real-time Isoprene fluxes from oak leaves, using a single living leaf, are measured as a function of light modulation.
Atmospheric concentrations of isoprene have been of inis terest for many years. Isoprene (2-methyl-1,3-butadiene) emitted by woody plants and deciduous trees in large quantities and its emission rate is species dependent, proportional to solar intensity, and leaf temperature ( 1 ) . It is often the most abundant non-methane hydrocarbon in forest canopies (2-4). Large emission rates combined with an extremely high reactivity toward the hydroxyl radical, OH (kisoprene+OH = 1.01 x cm3 molecule-' 5-l) (5), allow isoprene to dominate the daytime chemistry of atmospheric OH in many areas such as tropical forests (6). The atmospheric oxidation of isoprene is also of importance since the reaction products are important precursors for the formation of O3 in rural atmospheres ( 4 ) . In order to gain a better knowledge of natural hydrocarbon emissions and their impact on atmospheric quality, especially in relation to the anthropogenically modified, polluted atmosphere, studies have sought to measure ambient isoprene concentrations and profiles. Atmospheric isoprene concentrations have been measured by using grab sampling into stainless steel cannisters followed by gas chromatography analysis (2-4). Difficulties with this method are: (1)Instability of isoprene is such containers can lead to gradual loss with respect to time ( 2 , 7 , 8 ) ,especially at sub-part-per-billion-by-volume (ppbv) levels and low humidity or in the presence of ambient oxidants, which are also sampled into the cannisters. (2) Chromatographic analysis is relatively labor intensive, costly, and slow. Therefore only a limited number of samples can be collected and analyzed per day. This low frequency precludes characterization Of diurnal variability and adds difficulty in relating emission rates to environmental variables. In addition, data are not available in real time, thus prohibiting interactive refinement of experimental procedures. (3) The inherent slowness of the
technique precludes important eddy correlation flux measurements. Biological interest in isoprene is also very strong since isoprene emission has been linked to primary photosynthetic processes in many types of vegetation (9-11). The photosynthesis/isoprene emission relationship is thought to be on the order of seconds, but present analytical techniques require several minutes of sampling followed by longer periods of chromatographic analysis time. Thus, fundamental information regarding the basic mechanistic isoprene/photosynthesis relationship is obscured. Chemiluminescence (CL) is a technique that is amenable to real-time monitoring of certain atmospheric species. It is selective, owing to the relatively small number of compounds that chemiluminesce upon reaction with a given reactant, and very sensitive since the chemiluminescence appears out of a near zero light background. In principle, a single photon generated from a chemiluminescent reaction can be detected. Useful chemiluminescence systems have been described for NO reacted with O3 (12-14), reduced sulfur and selenium compounds with Fz( 1 5 , 1 6 ) ,iodinated hydrocarbons with F2 (17),H2S and CH3SH with OClO (18),and halogenated organics with sodium vapor (19). The chemiluminescence of alkene/03 reactions has been explored as an ozone monitor (20), as GC detectors (8, 21, 22), and as ambient alkene monitors (23,24). Becker et al. (24)did not report a detection limit but Schurath (23) lists a detection limit of 3 ppb for the most sensitively detected alkenes. We describe here a real time detection system, sensitive to isoprene, based on the chemiluminescence reaction between a primary alkene and ozone alkene
+ O3
-
HCHO*+ products
(1)
Olefin/03 mechanistic studies have been made by Pitts et al. (25-29) and others (30). Emission from HCHO* (lA2)occurs in the region 450-550 nm. As a first step toward development of a sub-ppbv ambient atmospheric instrument, an application is presented in which isoprene flux is monitored from 7.1 cm2 of a single oak leaf, in real time. Leaf fluxes were measured as part of a biochemical study relating photosynthetic processes to isoprene production.
EXPERIMENTAL SECTION Instrumentation. To determine the best photomultiplier tube (PMT)/filter combination, O,/dkene spectra were collected Over the wavelength range 200-800 nm on a discharge-flowsystem described earlier (31, 32) coupled to an intensified diode array scanning spectrometer (IDARSS, TN 1710, Tracor-Northern). The IDARSS instrument was wavelength calibrated using a
0 1990 American Chemical Society 0003-2700/90/0362-1055$02.50/0
1056
ANALYTICAL CHEMISTRY, VOL. 62, NO. 10, MAY 15, 1990
5.5 cm long resulting in a cell volume of 108 mL. The cell was ultrasonically cleaned before use. A 0.5 cm diameter inlet in the rear of the chamber was used to admit isoprene mixtures or air flows. The O3 inlet in. 0.d.) was inside, and collinear with, the sample inlet. This "point" reaction region ensured the highest RC FILTER possible O,/isoprene concentrations and hence produced the maximum photon yield. Ozone partial pressures were measured with UV absorption at 254 nm in an absorption cell of path length PULSE DISCRIM 0.10 cm. The measurement method has been described elsewhere (33). Pressures were measured with capacitance manometers (MKS Baratron, Type 127A). Gases were evacuated near the window via a concentric slot circling the end of the chamber. Thus, % ELECTROMETER , + the reaction chamber was swept clean continually and the concentric pumpout slot helped preserve laminar flow conditions, resulting in minimal dead volume. A vacuum pump (SargentWelch, Model 1402) was used to evacuate the gases. Hopcalite sorbent protected the pump from damage due to ozone attack. Reaction cell connections were made via Swagelock VCO fittings. The reaction chamber and the PMT housing were sandwiched VACUUM around a 3 in. diameter, 1/16 in. thick glass window. Cell temperature could be varied via silicone heat tape and variable power supply. The photomultiplier tube (Hammamatsu R329-02, low dark-current selected) was operated in a custom-made variable temperature housing. The blue-sensitive R329-02 was chosen to have high quantum efficiency (25-10%) over the emission region, \ kl SAMPLE 425-550 nm, and low quantum efficiency (2.5% a t 600 nm and I ' AIR 0.1% a t 680 nm) at red wavelengths where NO + O3 chemiluminescence emission occurs. Signals were first processed by a fast electrometer (Analog Devices,AD549) and then via a pulse discriminator circuit (Figure 2). This circuit eliminated spurious large and wide signal spikes, those >4.0 V and >2 ms, and low level noise signals C0.2 V, which are thermally generated dynode currents. The upper and lower discriminator levels were variable but the upper level discriminator U was not set below 4 V, to avoid deviations from linearity a t high light fluxes. The fast discriminator circuitry lessened noise and, Figure 1. Schematic of the chemiluminescence detection system: hence, improved signal/noise, by a factor of 2-3. For most exF.C., flow controller. periments the selected pulse train was then RC filtered, T = 0.1-10 low-pressure helium discharge lamp and helium reference spectra. s, and fed into an HP 3392A plotter and a digital voltmeter. Both A schematic of the isoprene chemiluminescence detection photon counting and a light chopping technique, where light was system constructed is shown in Figure 1. The CL reaction cell chopped between the reaction cell and the PMT coupled to lock-in constructed of mirror-finish stainless steel is 5.0 cm diameter and detection, were investigated, but were found to be inferior to the
w I
I
4
+I5
9
TERMINAL
.IP LEVEL PI-UG
022"
$?IN4148
)LOW CLIP LEVEL BANANA PLUG
Figure 2. Electronic schematic of the pulse discrimination circuit.
ANALYTICAL CHEMISTRY, VOL. 62, NO. 10, MAY 15, 1990
[
1
,
200
1
'
1
1
300
I
l o *
'
1
1
1
400
1
500
I
1
600
I
1
I
1
700
'
1057
I
1
1
800
A (nm)
Figure 3. Chemiluminescence spectrum produced by the reaction of
isoprene with ozone: P = 7.9 lorr, 140 scans (70 signal background): F,, = 194 mllmin; F, = 3 mL/min.
+ 70
aforementioned signal processing method. In theory, photon counting can result in improved detection limits due to the advantages of counting statistics; however the ozonizer used to produce maximal ozone levels generated large rf fields and triggered counting equipment resulting in spurious photon counts. Gas Mixtures. Isoprene standards, 1.03-410 ppmv, were prepared by taking vapor of liquid isoprene (99+%, Aldrich Chemical Co.) and performing serial dilutions in He (UHP). Total pressure of the gas standards was 80-100 psi (4140-5170 Torr). The standards were calibrated by using gas chromatography and were referenced against NBS reference standards. Part-perbillion-by-volume (ppbv) levels of isoprene were prepared in real time by diluting a ppmv isoprene standard into argon (UHP). Gas flows were measured with Tylan (FM-360and FC-260) mass flowmeters and flow controllers. These were calibrated with a wet test flowmeter or bubble flowmeter and were referenced against new, factory calibrated, Tylan controllers. Leaf Fluxes. Isoprene emissions from white oak (Quercus alba),maintained in a greenhouse as previously described ( I ) , were measured in a temperature-controlled, 4 mL, aluminum/glass cuvette which sealed onto an intact living leaf. A gas-tight seal was made with rings of adhesive foam circling each side of the cuvette. This allowed the leaf to remain connected to the tree. Control over light intensity, leaf temperature, relative humidity, and air composition (including COz and Oz) was maintained by using the system previously reported (34). The air mixture flowed continuously over both surfaces of the leaf at 300-600 mL/min (all flows are STP mL/min). Water vapor was found to have only a small effect on chemiluminescence sensitivity; however it markedly quenched background chemiluminescence signals. Thus, rapid humidity changes would be expected to cause base-line shifts. For this reason a drier was put in line between the leaf cuvette and the isoprene instrument. The drier, previously referenced (35), consisted of a Nafion tube through which the sample flowed, and a small countercurrent dry nitrogen flow, which removed HzO vapor diffusing through the Nafion. Use of the drier prevented base-line shifts and/or chemiluminescencesensitivity variation even at high humidity levels (up to 90% relative humidity tested). The measurement of isoprene fluxes required an accurate knowledge of instrument sensitivity. Sensitivity was measured daily by recording instrumental response for a standard isoprene mixture. Part-per-billion-by-volumestandards, prepared as stated above, were mixed into the controlled composition air, and flowed over the leaf in dark conditions. In this way any systematic isoprene losses, such as cuvette leakage, would be taken into account. Day to day sensitivity was found to vary by at most 5%.
RESULTS AND DISCUSSION Spectra. The IDARSS spectrum obtained upon reaction of isoprene with ozone is shown in Figure 3. This spectrum is qualitatively similar to most 03/alkene spectra. The largest peak having a maximum a t = 490 nm is due to excited-state
...a
...I I...
Figure 4. Signal produced by 3.1 ppbv isoprene under the conditions: P = 423 Torr: Fo2 = 200 mL/min; FA, = 452; T = 14 O C ; 24 mV
signal: SIN =
2
at
400
ppbv.
formaldehyde emission. The second peak in the spectrum a t = 550 nm is probably emission from excited-state glyoxal (CH0)2*. Excited-state glyoxal can be formed in the reaction of ozone with an alkene (such as isoprene), if the alkene possesses one or more alkyl groups bonded to the carbon of a carbon-carbon double bond (36).The isoprene/03 spectrum was compared to an ethene/03 emission and to spectra for various ozone chemiluminescence reactions. The ethene/03 spectrum is similar to Figure 4 except only emission from HCHO*is observed. The ethene/03 spectrum was compared to literature spectra for this reaction and was found to be qualitatively the same. The reaction of various monoterpenes, a- and /3-pinene, limonene, and a neat mixture of 33 different monoterpenes, with ozone, generated light, but only a t very low levels. Chemiluminescence from monoterpenes was observed with a P M T but was too weak for recording IDARSS spectra. This was somewhat surprising since monoterpenes are known to react rapidly with ozone. Apparently, either they do not produce excited-state species upon reaction with 03, or the monoterpenes, or other reaction products quench these species prior t o their fluorescence. Optimization. The isoprene chemiluminescence instrument was operated over a wide range of conditions: pressure (1Torr to atmosphere pressure), O2 flow (40-300 mL/min), Ar buffer gas (0-300 mL/min), reaction temperature (0-70 "C), reaction time (0.10-30 s), P M T voltage (-1253 to -1570 V dc), and P M T temperature (-15 to 35 "C). Since the P M T signal is proportional to the amount of light produced in the reaction cell, as long as there is sufficient ozone in the reaction chamber, signal will increase as isoprene flow is increased. System sensitivity is therefore mass dependent as opposed to concentration dependent. Throttling of the system pump to boost O3 concentration and increase extent of reaction, also raised system sensitivity (defined as volts of signal per ppbv isoprene) up to about 400 Torr where sensitivity flattened. Optimal pressure, 300 Torr, was obtained by balancing increased sensitivity a t higher pressures with increased dead time of the reactor. Above ambient reaction temperatures were normally employed to ensure a constant reaction cell temperature. Elevated temperatures favored the 03/isoprene reaction (koa+lsoprene= 1.23 X exp-2020/T)cm3 molecule-' s-l (37,38). Temperatures above 60 O C were not used since heating the photocathode of the P M T increased instrumental background and noise. Also, discrimination against alkanes and other more reactive compounds lessens a t very high
1058
ANALYTICAL CHEMISTRY, VOL. 62, NO. 10, MAY 15, 1990
1 second
u
-2 -a
.-m VI
0
100
200
300
I
400
isoprene (ppbv)
Figure 5. Plot of isoprene concentration (ppbv) versus instrument signal output (V).
temperatures. Optimal operating temperature was found to be about 50 "C. Other optimal operating parameters were O2flow (200 mL/min), Ar buffer gas or air inlet (200 mL/min), applied P M T voltage (-1570 V dc), and P M T temperature (ambient). For a reaction cell volume of 108 mL, the residence time, calculated for the conditions above and corrected to non-STP conditions, was 5.4 s. A calculation of extent of reaction completion was made based on the above conditions and measured ozone concentrations. At a typical ozone partial pressure of 22 Torr (2.4 X 10'' molecules/mL), one calculates Z 99.99% reaction completion. Further sensitivity improvements may be realized through more inert and reflective reaction cell materials, i.e. externally silvered glass. It should be noted that the gold coating of reaction cells, normally used in NO/03 CL systems, works poorly for the shorter wavelengths of this system. The detection limit for isoprene, defined as twice the average noise level, is 400 pptv. Figure 4 shows a CL trace resulting from 3.1 ppbv of isoprene in Ar, with the isoprene mixture flow on then switched off. The instrument described here is about 4 times more sensitive than the instrument of Schurath et al. (23) (compared by using matched time constants of 6 s). Since detector sensitivity is proportional to both O3concentration and reaction time, under fast reaction conditions, low pressures, and 10 in regions where isoprene fluxes are sig-
ANALYTICAL CHEMISTRY, VOL. 62, NO. 10, MAY 15, 1990
c
2
*
e
B
I O 3 2
3.
l l
minutes
Flgure 7. Upper plot: 3 min on/3 min off cycling of isoprene standard through cuvette system in dark conditions. Lower plot: white oak isoprene flux under white light modulation, sampled from lower leaf surface. Light modulation sequence; off-on-off. Isoprene rise time to >98% signal = 7 min. Fall time to 300 "C. This will be investigated shortly. ACKNOWLEDGMENT The authors wish to thank the Atmospheric Chemistry Division electronics department of NCAR for circuit design, Brian Ridley and Tony Delaney for helpful discussion, Chris Ennis and James Greenberg for technical assistance, and John Birks and Ray Fall of The University of Colorado for helpful
1060
Anal. Chern. 1990, 62, 1060-1064
discussion and use of equipment. Reaistm No. HCHO, 50-00-0; OR,10028-15-6; isoprene, 78-79-5.
LITERATURE CITED Monson, R. K.; Fall, R. Plant Physiol. 1989, 90,267-274. Greenberg, J. P.; Zimmerman, P. R. J . Geophys. Res. 1984. 89, 4767-4778. Zimmerman, P. R.; Greenberg, J. P.; Westberg. C. E. J . Geophys. Res. 1988, 93, 1407-1416. Rasmussen, R. A.; Khalii, M. A. K. J . Geophys. Res. 1988, 93, 1417-1421. Finlayson-Pitts, B. J.; Pitts, J. N., Jr. Atmospheric Chemistry: Fundamentals and Experimental Techniques; John Wiley and Sons, Inc.: New York, 1986; p 432. Jacob, D.J.; Wofsy, S. C. J . Geophys. Res. 1988, 93, 1477-1486. Holdren, M. W.; Westberg, H. H.; Zimmerman, P. R . J . Geophys. Res. 1979, 8 4 , 5083-5088. Seila, R. L. Int. Conf. Photochem. Oxid. Poll. Control Proc., 1, PB-264, 232, EPA-600/3-77-001a; US. Environmental Protection Agency, Office of Research and Development: Cincinnati, OH, 1976; pp 41-50. Evans, R . C.; Tingey, D.T.; Gumpertz, M. L.; Burns, W. F. Bot. Gaz. 1982, 743, 304-310. Rasmussen, R. A. Environ. Sci. Technol. 1970, 4 , 667-671. Zimmerman, P. R . Final Report, EPA-450/4-79-004. 1979. Ridley, B. A,; Howlett, L. C. Rev. Sci. Instrum. 1974, 45, 742-746. Ridley, 6. A. A t m s . Tech. 1978. 9 ,27-34. Kiey, D.;McFarland, M. Atmos. Tech. 1980, 72, 63-69. Nelson, J. K.; Getty, R. H.; Birks, J. W. Anal. Chem. 1983, 5 5 , 1767-1770. Glinski, R. J. J . Phys. Chem. 1989, 93, 1913-1915. Getty, R. H.; Birks, J. W. Anal. Lett. 1979, 72, 469-476. Spurlin, S.R.; Yeung, E. S.Anal. Chem. 1982, 5 4 , 320-321. Yamada, M.; Ishiwada, A,; Hobo, T.; Suzuki, S.;Araki, S.J . Chromatogr. 1982, 238,347-356. Warren, G.J.; Babcock, G. Rev. Sci. Instrum. 1970, 4 7 , 280-281. Rao, A. M. M.; Netravalkar, A. J.; Arora, P. K.; Vohra, K. G. Atmos. Environ. 1983, 77, 1093-1097. Bruening, W.; Concha. F. J. M. J . Chromatogr. 1975. 772, 253-265. Schurath, U.; Wiese, A,; Becker, K. H. Staub-Reinhalt. Lutt 1976, 9 , 379-385. Becker, K. H.; Schurath. U.; Wiese, A. US. Environ. Protec. Agen. Off. Res. Dev., [Rep.] E.P.A., 1976, EPA-600/3-77-001a, Int. Conf. Photochem. Oxid. Poll. Control Proc., 1, PB-264. 232, 31-40.
(25) Finlayson-Pitts, B. J.; Pitts, J. N.. Jr. Atmos. Chem. 443-459. (26) Finlayson, B. J.; Pitts, J. N., Jr.; Atkinson. R. J . Am. Chem. Soc. 1974, 96,5356-5367. (27) Finlayson, B. J.; Pitts, J. N., Jr.; Akimoto, H. Chem. Phys. Lett. 1972, 72. 495-498. (28) Kummer. W. A.; Pitts, J. N., Jr.; Steer, R. P. Environ. Sci. Technol. 1971. 5 . 1045-1047. ~. (29) Hansen, D. A.; Atkinson, R.; Pitts. J. N., Jr.; Steer, R. P. J . Photochem. 1977, 7 , 379-404. (30) Kamens, R. M.; Gery. M. W.; Jeffrles, H. E.; Jackson, M.; Cole, E. I . Int. J . Chem. Kinet. 1982, 74, 955-975. (31) Hills, A. J.; Cicerone, R. J.; Calvert, J. G.; Birks, J. W. J . Phys. Chem. 1987, 9 7 , 1199-1204. (32) Hills, A. J.; Cicerone, R. J.; Calvert. J. G.: Birks, J. W. J . Phys. Chem. 1988, 92, 1853-1858. (33) Stimpfie, R. M.; Perry, R. A.; Howard, C. J. J . Chem. Phys. 1979, 7 7 , 5183. (34) Monson. R. K.: Moore. B. D.;Ku. M. S.B.; Edwards, G. E. Pknta 1988. 768,493-502. (35) Benner, R. L.; Lamb, E. J . Atmos. Ocean. Tech. 1985, 2 , 582-589. (36) Toby, S. Chem. Rev. 1975, 8 4 , 277. (37) Atkinson, R.; Winer. A. M.; Pitts, J. N., Jr. Atmos. fnviron. 1982, 76, 1017-1020. (38) FiniaysonIPitts, B. J.; Pitts, J. N., Jr. Atmos. Chem. 443. (39) Weast, R. C.: Astle. M. J. Handbook of Chemistry and Physics. 57th ed.; CRC Press: Cleveland, OH, 1976; p C-216. (40) Akimoto. H.; Finlayson, B. J.; Pitts, J. N., Jr. Chem. Phys. Lett. 1971, 72,199-202. (41) Kummer, W. A,; Pitts, J. N., Jr.; Steer, R. P. Environ. Sci. Technol. 1971, 5 , 1045-1047. (42) Andreae. M. 0.; Andreae, T. W. J . Geophys. Res. 1988, 93, 1487-1497. (43) Jacob, D. J.; Wofsy, S. C . J . Geophys. Res. 1988, 93, 1477-1486. (44) Kelly, T. J.; Gaffney, J. S.;Phillips. M. F.: Tanner, R . L. Anal. Chem. 1983. 55, 138-140.
RECEIVED for review December 5, 1989. Accepted February 8,1990. This work was supported by the Atmospheric Division and Advanced Study Program of the National Center for Atmospheric Research. A.J.H. thanks the Advanced Study Program of the National Center for Atmospheric Research for providing a Postdoctoral Research Fellowship.
Comparative Study of Sotid-Matrix Luminescence Interactions of p-Aminobenzoate on Two Different Matrices S. M. Ramasamy and R. J. Hurtubise*
Chemistry Department, University of Wyoming, Laramie, Wyoming 82071
The lumbwcence propertles of the anion of p-aminobenzoic acid adsorbed on sodium acetate and filter paper were compared to galn Insights Into the lnteractlons that result In the fluorescence and phosphorescence of p -amlnobenzoate. Fluorescence quantum yields, phosphorescence quantum ylelds, and phosphorescence lifetimes were obtained for the anlon of p-aminobenzoic acid adsorbed on filter paper. Preexponentlaland actlvatlon energy terms were calculated for p-amhwbenzoate on filter paper and compared with similar terms for p-amlnobenzoate adsorbed on sodium acetate. I t was shown that there was a simple relationship between the reciprocal of the phosphorescence lifetlmes and the thermal processes that cause deactlvatlon of the triplet state. I t was concluded that p-amlnobenzoate Is Incorporated into the crystal structure of sodlum acetate and the triplet energy of p-amlnobenzoate was lost prbnarlly via skeletal vibrations In NaOAc. For the anion of p-amlnobenzoic acid on filter paper, some of the triplet energy was lost through vlbratlonal modes In the filter paper, although other factors would also be Involved tn the loss of the triplet-state energy.
INTRODUCTION Room-temperature phosphorescence (RTP) and roomtemperature fluorescence (RTF) analysis from organic compounds adsorbed on solid matrices have been shown to be very effective approaches in organic trace analysis (1-3). New experimental conditions ( 4 ) and solid matrices (5) are still being reported for organic species adsorbed on solid materials. In addition, analytical luminescence figures of merit have been compared for several solid matrices and model compounds (6). Various models for the RTP of adsorbed compounds have been reviewed (1-3). The temperature effects on the solidmatrix luminescence properties of 4-phenylphenol adsorbed on filter paper have been reported (7). Also, the results from varying the temperature from 23 to -180 "C for benzo[flquinoline adsorbed on filter paper indicated that the modulus of filter paper was an important factor in enhancing the phosphorescence quantum yield of benzo[flquinoline (8). In addition, a variety of interactions have been revealed for several compounds adsorbed on 80% a-cyclodextrin-NaC1
0003-2700/90/0362-1060$02.50/0 0 1990 American Chemical Society
