Instrumentation
Robert J. Hurtubise Chemistry Department University of Wyoming Laramie, Wyo. 82071
PHOSPHORIMETRY New developments include solid-surface, micelle-stabilized, and solution-sensitized room-temperature phosphorescence Luminescence is the term used for both fluorescence and phosphorescence. This article will consider the phosphorescence of organic compounds, and emphasis will be given to instrumentation and applications. Lewis and Kasha (1) identified the phenomenon of phosphorescence in 1944. Several analytical uses of phosphorescence were evaluated by Kiers, Britt, and Wentworth (2). In 1958, Freed and Salmre (3) reported the construction of a phosphorimeter. Later, in 1962, Parker and Hatchard (4) modified a spectrofluorimeter for measuring phosphorescence spectra. In 1963, Winefordner and Latz (5) constructed a phosphorimeter and used it for the determination of aspirin in blood serum. Over the years a considerable amount of work in phosphorimetry has been carried out by Winefordner and co-workers. Recent developments in room-temperature phosphorescence (RTP) have attracted the interest of several research groups. The fundamental theoretical aspects of phosphorescence have been documented in the literature (6, 7) and will not be discussed in detail; only a brief comparison between fluorescence and phosphorescence will be given. Fluorescence involves a radiative transition from the lowest vibrational level of the lowest excited singlet state to a singlet ground state of a molecule. Phosphorescence occurs when there is a radiative transition from the lowest vibrational level of the 0003-2700/83/0351 -669A$01.50/0 © 1983 American Chemical Society
lowest triplet state to a singlet ground state of a molecule. The decay time of fluorescence is in the range of 10~ 9 to 10~7 s, whereas phosphorescence has a decay time from approximately 10~4 to 10 s. A transition from an excited singlet state to the singlet ground state is a spin-allowed transition and occurs with a high degree of
probability. A transition from an excited triplet state to the singlet ground state, however, is a spin-forbidden transition and is highly improbable. This fact gives a triplet electronic state its long lifetime, greatly increasing the probability of collisional transfer of energy with other molecules, such as solvent molecules. This pro-
Figure 1. Schematic diagram of an AutoAnalyzer continuous filter with the roomtemperature phosphorescence detection system 1) Light source, 2) excitation monochromator, 3) rotation motor-phosphoroscope, 4) reflecting surface, 5) optics, 6) filter paper, 7) emission monochromator, 8) detection unit, 9) recorder, 10) filter paper roll, 11 ) spotting syringe, 12) drying IR lamp, 13) dry air supply, 14) AutoAnalyzer continuous filter. Reprinted from Reference 30 ANALYTICAL CHEMISTRY, VOL. 55, NO. 6, MAY 1983 · 669 A
cess is very efficient in solution at room temperature and is often the main pathway for loss of triplet state energy. Solution analytical phosphorimetry usually involves measuring the phosphorescence of the phosphor at the temperature of liquid nitrogen in a solvent that freezes to form a rigid glass at liquid nitrogen temperature (77 K). New developments in phosphorimetry have shown that analyti cally useful phosphorescence can be obtained at room temperature from phosphors adsorbed on solid surfaces (8), by micelle-stabilized phosphors in solution (9), and by phosphor-sensi tized R T P in solution (10). Solution Low-Temperature Phosphorimetry As Ward and co-workers (11) have discussed, little has been done since 1975 in the area of solution low-tem perature phosphorimetry. The lack of widespread use probably is related to the need for cryogenic equipment and the problems involved with introduc ing the sample into the phosphorimetric system. For example, a long quartz capillary cell is slowly lowered into a quartz Dewar flask filled with liquid nitrogen. Depending on the rate of cooling of the sample cell and the chemical nature and composition of the solvent system, the cooled matrix can be a clear glass, a cracked glass, or a snow. A skilled technician or chem ist, however, can obtain very good data with low-temperature phospho rimetry. The major advantages of so lution low-temperature phosphorime try are low detection limits (nanomo lar range), linear analytical calibration curves of wide range, and very good selectivity. Most commercial phosphorimeters employ immersion cooling of the sam ple with liquid nitrogen. Two new con duction cooling devices for low-tem perature phosphorimetry that cool a short capillary sample cell in a copper block cooled by liquid nitrogen have been discussed by Ward et al. (12,13). These devices have reduced the amount of liquid nitrogen normally re quired, lowered cost because an opti cal-grade quartz Dewar is not re quired, and improved sample turnover time to about one sample/min. Solid-Surface Room-Temperature Phosphorimetry In 1967, Roth (14) listed the R T P detection limits of 18 compounds ad sorbed on filter paper. The current in terest in R T P was most likely stimu lated by reports from Schulman and Walling (15, 16). In 1974, Paynter et al. (17) reported the range of linearity and detection limits for several com pounds adsorbed on filter paper. The field of analytical solid-surface R T P
has expanded considerably since their report. Calibration curves have a wide linear range, detection limits are in the subnanogram or nanogram region, and the precision ranges from about 3% to 10% depending on the solid sur face and experimental conditions. Re cent reviews and reports on analytical solid-surface R T P can be consulted for details (8,11,18,19). No general model has been devel oped to explain the interactions re quired for R T P from compounds ad sorbed on solid surfaces. However, some general trends have emerged. In most cases, the adsorbed phosphor must be dried to enhance the R T P sig nal. The effects of moisture and oxy gen on the R T P of sodium 4-biphenylcarboxylate and sodium 1-naphthoate adsorbed on filter paper were investi gated (20). From this work, it was pro posed that hydrogen bonding of ionic organic molecules to hydroxyl groups of the filter paper is the primary mechanism of providing the rigid ma trix for RTP. Presumably the rigid matrix minimizes collisional deactiva tion of phosphor molecules in the trip let state. In addition, it was noted that moisture acts to disrupt hydrogen bonding and aids in the transport of oxygen, which is a quencher, into the sample matrix. For p-aminobenzoic acid adsorbed on sodium acetate, strong R T P was observed (21). The main interactions proposed with this system were the formation of the sodium salt of p-ami nobenzoic acid and hydrogen bonding of the amino group of the acid with the carbonyl group of sodium acetate. Niday and Seybold (22) have suggest ed that packing the solid support with materials such as salts or sugars inhib its the internal motion of the phos phorescent compound. Further, the added compounds "plug u p " the chan nels and interstices of the matrix and thus decrease the oxygen and moisture permeability. Hurtubise and Smith (23) reported relatively strong R T P from the dianion of terephthalic acid adsorbed on a mixture of the anion of polyacrylic acid and sodium chloride. With the previous system, hydrogen bonding was not possible. In addition, Bower and Winefordner (24) showed that several polycyclic aromatic hy drocarbons give R T P on sodium ace tate and filter paper with a heavy atom present. It is clear from the liter ature that no single working model for solid-surface R T P has been devel oped. Room-Temperature Phosphorescence in Micellar Solutions Cline Love and co-workers (9, 25) have developed the new analytical ap proach of solution micelle-stabilized
670 A · ANALYTICAL CHEMISTRY, VOL. 55, NO. 6, MAY 1983
RTP. Phosphorescence can be ob served from many aromatic molecules in fluid solution at room temperature by incorporating the phosphor into a micellar system. Generally, a deter gent concentration above the critical micelle concentration is used to ensure micelle formation, heavy atoms are employed, and an inert gas is used to deoxygenate the sample solution. Limits of detection typically are in the nanomolar range and calibration curves have a wide linear dynamic range. The overall precision is about 6% (9). The sensitivity observed is somewhat surprising because of the large amount of radiationless deacti vation that may occur in solution at room temperature. Apparently the mi celle can organize reactants on a mo lecular scale and increase the proximi ty of the phosphor and heavy-metal counterion. This would raise the "ef fective" concentration of the heavy metal and increase the probability of spin-orbit coupling. Other factors are also involved (9). Limits of detection and micelle-stabilized R T P tripletstate lifetimes were reported for aro matic ketones, aldehydes, alcohols, carboxylic acids, and amines (25). Sensitized Room-Temperature Phosphorescence in Liquid Solutions Phosphorescence intensities in liq uid solutions are generally too low to be useful in analytical work. However, Donkerbroek et al. (10, 26) recently investigated R T P of phosphors in liq uid solutions without the use of mi celles. They concluded that direct so lution R T P of phosphors with intensi ties high enough to be useful in ana lytical chemistry is rather rare. A use ful alternative is sensitized phospho rescence in solution at room tempera ture. As applied by Donkerbroek et al., sensitized phosphorescence can be described as follows: After excitation and before radiationless decay of the analyte, the analyte transfers its trip let-state energy to an acceptor mole cule and then the acceptor molecule emits phosphorescence. 1,4-Dibromonaphthalene and biacetyl have been investigated as acceptors in solvents frequently used in liquid chromatog raphy, and guidelines for good accep tors have been discussed (10, 26). Limits of detection for several substi tuted benzophenones and biphenyls in acetonitrile:water (1:1) were in the range of Ι Ο - 8 Μ (10). Solution-sensi tized phosphorescence should be feasi ble for many analytes that do not fluo resce but do phosphoresce. Instrumentation Commercial instruments for mea suring phosphorescence intensities,
lifetimes, excitation spectra, and emission spectra are well documented in the literature (27). Commercial instruments are employed in low-temperature phosphorescence, solid-surface RTP, MS-RTP, and solution-sensitized RTP studies. Modifications to commercial instruments for work in the previous areas can be relatively minor or very sophisticated depending on individual needs. Cline Love et al. (9, 28) have constructed a phosphorimeter from commercially available components and have used it in M S RTP. Ford and Hurtubise (29) constructed a phosphoroscope and modified a reflection mode assembly for a spectrodensitometer to measure R T P from solid surfaces. Vo-Dinh et al. (30) designed an automatic phosphorimetric instrument for solid-surface RTP with a continuous filter paper device as shown in Figure 1. Later, Bower and Winefordner (31) designed a modified version of the above system with a filter paper guide that allowed continuous sampling of organic phosphors adsorbed on filter paper. Walden and Winefordner (32) emphasized that one problem with most commercial luminescence instruments is that only a small fraction of the total emitted luminescence is collected and measured. They made a comparison of ellipsoidal and parabolic mirror systems that partly compensated for this problem and employed the systems in solid-surface RTP work. Hurtubise (33) has considered other aspects of the instrumentation developed for solid-surface RTP. Fisher and Winefordner (34) first showed the experimental importance of pulsed-source time-resolved phosphorimetry. This approach is useful for analyzing mixtures of fast-decaying phosphors. Figure 2 shows one cycle of sample excitation and observation for a pulsed-source gated-detector phosphorimeter system (34). After an initial pulse of source energy, with a duration tj, the phosphorescence intensity climbs to a maximum peak value and then decays exponentially. At a delay time, tj, after the source flash has decayed significantly, the multiplier phototube is turned on and the phosphorescence signal is monitored. The multiplier phototube is then turned off and the sequence is repeated. The integrated luminescence intensity is measured during the "on" time, tp, of the phototube. Three variations of pulsed-source phosphorimetry that can be used to determine phosphors in binary and multicomponent mixtures have been discussed (34). The application of pulsed-source phosphorimetry to the quantitative and qualitative analysis of drugs has been reported (35). In this application, a xenon flashtube
(11). Figure 3 shows a block diagram of the pulsed-laser time-resolved phosphorimeter. Wilson and Miller (38) developed a computer-controlled laser phosphorimeter in which the phosphorescence spectra were recorded on magnetic tape as signal-averaged families of decay curves. With the phosphorescence emission data in this form, timeresolved phosphorimetric studies were possible without the aid of mechanical or electronic chopping devices. Generally the data were acquired once and then could be displayed as desired using almost any time window of in-
source was used instead of the standard continuously operated xenon-arc source and phosphoroscope. In addition, either a boxcar averager for temporal information at one value of t^ or a signal averager for information at several values of ta was used. Recently, Boutilier and Winefordner (36, 37) used both a pulsed N2 laser or a flashtube-pumped dye laser in place of the pulsed xenon source. The main reasons for using a laser were the clean temporal characteristics of the laser pulse and the ability to perform time resolution to enhance the sensitivity and selectivity of the measurement
Figure 2. Schematic diagram of events occurring during one cycle of sample excitation and observation in a pulsed-source phosphorimeter system Key to symbols and lines in diagram: tf = half-intensity width of the source flash; td = delay time after the end of the excitation pulse (assuming excitation pulse to be rectangular) to the beginning of observation of the phosphorescence signal " o n " time of the detector or the readout system; fp = " o n " time of detector or readout system; dashed line represents buildup and decay of phosphorescence; solid white curve represents flash intensity temporal distribution; rectangular pulse represents " o n " time of detector or readout system; yellow area represents measured integrated luminescence signal per source pulse. Reprinted from Reference 34
Beam Steering Mirrors Lens
Laser HighVoltage Power Supply
Excitation Filter Sample Housing
Chart Recorder
Gated Amplifier Signal
Monochromator Emission Filter
N2_ Flush
Boxcar Integrator
Computer
t*M.M,:|TO
PM Tube
Oscilloscope
Signal Averager
Figure 3. Block diagram of pulsed-laser time-resolved phosphorimeter Reprinted f r o m Reference 36
672 A • ANALYTICAL CHEMISTRY, VOL. 55, NO. 6, MAY 1983
Tape Punch
Flash Lamp
Sample Chamber
Pulsed Power Supply
,HG Power Supplies
Emission Spectrograph
Control Logic
Signal Processing
Command Decoder
Diff. Amp ADC
Scope Real-Time Display
Disk
Interface
TTY
Tape
Computer PDP 8/M
Plotter
Figure 4. Block diagram of SIT-based time-resolved phosphorimeter Reprinted from Reference 39
terest. This allowed one to conduct detailed kinetic analyses of the decay processes influencing emission. Wilson and Miller emphasized that further refinement of this technique is need ed, such as adjustment of the time lapse between the data acquisition and the display of the reconstructed spectrum. Goeringer and Pardue (39) dis cussed the development of a time-re solved phosphorescence spectrometer with a silicon intensified target (SIT) vidicon camera system and a pulsed source. The instrument permitted time-resolved spectra to be recorded with a minimum scan time of 8 ms/ scan. Spectral decay data were pro cessed by a variety of regression meth ods to obtain rate constants, lifetimes, and initial intensities. Figure 4 shows a block diagram of the system. Both temporal and spectral data were used to analyze data from the room-tem perature phosphorescence of com pounds adsorbed on filter paper for single-, two-, and three-component mixtures. Mousa and Winefordner (40) devel oped the new analytical approach of phase-resolved phosphorimetry. This method depends on the phase resolu tion of the phosphorescence signal from species with different lifetimes, and a phosphoroscope is not needed. Because of the different phase and amplitude relationships of their phos phorescence signals, mixtures of struc turally similar organic compounds can be analyzed. Mousa and Winefordner
(40) derived equations describing the phase and frequency characteristics of the phosphorescence and gave guide lines for the use of the equations in various analytical situations. It has been shown that phase-resolved phos phorimetry does not have the superior noise-rejection characteristics of timeresolved phosphorimetry (41). Phaseresolved phosphorimetry probably will find little use other than for measure ments of phosphorescence lifetimes from the phase-angle relationship. Ho and Warner (42) discussed a new approach to phosphorimetry for multicomponent samples by the rapid acquisition of multiparametric data. The phosphorescence data are ac quired in the form of emission-excita tion matrices. Workers at the Univer sity of Washington (43) developed a new fluorescence instrument, called a video fluorometer, which used a novel illumination method to obtain simul taneous multiwavelength excitation of a fluorescent sample. The illumination method employed a vertically dis persed polychromatic beam of source radiation to directly excite the sample in a cuvette. The fluorophor absorbed the exciting radiation and several bands of fluorescence emanated from the cuvette. With the instrumental system, information was provided in stantaneously on the excitation prop erties of the fluorophor. Spatial infor mation along the vertical axis of the cuvette was maintained while each of the excitation bands was dispersed horizontally into its component emis
674 A · ANALYTICAL CHEMISTRY, VOL. 55, NO. 6, MAY 1983
sion. A two-dimensional image of fluo rescence intensity as a function of ex citing and emitting wavelengths was provided at the exit plane of the emis sion polychromator. Mathematical ex pressions were used in representing the fluorescence emission-excitation matrix, and linear algebra and com puter algorithms were used for both qualitative and quantitative analysis of fluorescence data (44, 45). Similar mathematical techniques were used by Ho and Warner (42) for the phospho rescence emission-excitation matrix. The video fluorometer system was modified slightly to obtain the phos phorescence emission-excitation ma trix. For fluorescence measurements, the excitation source was continuous, and the observed fluorescence signal reached steady-state conditions before the data were acquired. With the phosphorescence experiments, the ex citation source was cut off completely so only the phosphorescence signal was observed. The multidimensional phosphorimetric approach developed by Ho and Warner (42) illustrates the need to couple instrumental methods with mathematical algorithms for si multaneous multiparametric lumines cence measurements. The selectivity of phosphorimetry can be increased by synchronous phosphorimetry as proposed by VoDinh and Gammage (46, 47). With this technique, the excitation and emission monochromators of a phos phorimeter are set at a constant wave length of separation (Xem — λ βχ = Δλ). Then both monochromators are scanned at the same rate. This ap proach gives sharp phosphorescence peaks and can minimize contaminant phosphorescence if Δλ for the analyte is substantially different from the con taminant. Vo-Dinh (47) also has pro posed the use of projections in two di mensions, namely, emission-excita tion maps in conjunction with syn chronous phosphorimetry. Recently Inman and Winefordner (48) have suggested that constant energy syn chronous luminescence spectroscopy could be directly applied to low-tem perature phosphorimetry. This ap proach awaits further development. In still another approach, second-deriva tive phosphorescence was used by VoDinh and Gammage in room-tempera ture phosphorescence work (49). The overlap between phosphorescence emission bands was reduced as was phosphorescence background interfer ence. It is clear from the discussion that a wide range of phosphorescence instru mentation is available—from commer cial units to highly sophisticated re search instruments. Many of these in struments allow data to be obtained more easily than in the past and allow
considerable versatility in handling and manipulation of data. Some of the instrumental advances that should ap pear in the future are greater use of la sers, conduction cooling devices, and TV detectors (11). Very recently, Warren et al. (50) used a phosphores cence experimental measurement sys tem that was controlled by a master microprocessor. Input and output de vices included a teletypewriter, ther mal plotter/printer, and a video mon itor. Analytical Data and Applications A large body of phosphorescence analytical data has been reported for a variety of organic compounds. Most of the data are for compounds in solution at low temperature and compounds adsorbed on solid surfaces at room temperature. Which of the four phosphorimetric approaches (low-tempera ture, RTP from surfaces, micelle-sta bilized RTP, or solution-sensitized RTP) one would use depends on sev eral factors including the particular analytical problem, available instru mentation, cost, and sensitivity. How ever, to determine the "maximum" phosphorescence yield from a phos phor one would use low-temperature phosphorimetry because collisional deactivation would be minimized at low temperature. If a compound does not yield a low temperature phospho rescence signal, then the probability is very small that it will yield an analyti cally useful RTP signal by any of the three R T P approaches. Some of the
advantages of R T P from solid surfaces compared to low-temperature phos phorimetry are: The analytical proce dure is simpler, there is no time-con suming solution degassing and no cryogenic equipment, automation for routine analysis is possible, and the selectivity is greater (11). With fur ther developments in and under standing of micelle-stabilized RTP, many more applications to a variety of compounds should appear with this new analytical technique. Sensitized R T P is an indirect analytical method and should find several specialized ap plications. For the remainder of this article, se lected examples will be discussed to show the wide range of samples that can be investigated by phosphorime try. One of the first applications of solid-surface RTP was the determina tion of p-aminobenzoic acid in multicomponent vitamin tablets (51). The limit of detection was 0.5 ng, and the method was shown to be more sensi tive than the USP XVII method. The selectivity of the method was very good because p-aminobenzoic acid was determined without prior separa tion. Several components were present in the tablets: vitamin Bi, vitamin Β·2, vitamin Ββ, folic acid, p-aminobenzoic acid, pantothenic acid, niacinamide, inositol, choline bitartrate, vitamin Bi2, and biotin. Benzo[/]quinoline and phenanthridine were identified using both fluorescence and phosphores cence excitation and emission spectra after separation from a shale oil sam
ple (52). Vo-Dinh and Gammage (46) used synchronous solid-surface RTP to identify pyrene in an extract of a Synthoil sample. Figure 5 shows the scans for the Synthoil sample and py rene standard. Solid-surface RTP was used later to identify and quantify polycyclic aromatic hydrocarbons in a Synthoil synthetic fuel sample (53). Several trace and major components were identified and determined from tens to thousands of parts-per-million. The selectivity was improved by using heavy-atom perturbation and syn chronous excitation scanning. Other applications of solid-surface RTP have also appeared for the determina tion of polycyclic aromatic hydrocar bons in coal liquids (54). Weinberger et al. (55) have exam ined the usefulness of micelle-stabi lized R T P for detection and quantita tion of aromatic molecules in highperformance liquid chromatography. A micellar mobile phase of sodium/ thallium lauryl sulfate was used for both micellar chromatography and de tection because all reagents needed for micellization and phosphorescence en hancement were readily added to the system. As an alternative approach, reversed-phase separations were per formed and then the micellar reagents were introduced postcolumn. Several experimental parameters and condi tions were investigated. Generally the micelle-stabilized R T P approach was less sensitive than fluorescence for the compounds studied. One of the princi pal advantages of micelle-stabilized
Figure 5. Identification of pyrene in Synthoil by synchronous RTP analysis (Δλ = 250 nm): spectrum of Synthoil (black curve); spectrum of pure pyrene (yellow curve)
Figure 6. Total phosphorescence contour diagram for Forties crude oil (100 μΐ L~1, EPA glass, 77 K)
Reprinted from Reference 46
Reprinted with permission of Royal Society of Chemistry from Reference 61
676 A · ANALYTICAL CHEMISTRY, VOL. 55, NO. 6, MAY 1983
R T P was less spectral interference and greater selectivity by detection of signals in the red region of the spec trum, which is essentially less crowded than the lower wavelength region. O'Donnell and Winefordner (56) have reviewed the use of phosphorimetry in clinical chemistry. They stated that the greatest use of phosphorimetry in the clinical laboratory will be for the analysis of those molecular species that are difficult or impossible to mea sure by conventional methods. Medi cally, phenothiazine derivatives are an important family of compounds. Gifford et al. (57) reported detection lim its and phosphorescence lifetimes at 77 Κ for commonly used phenothiazines. In the pharmaceutical area, de Silva et al. (58) listed the low-tem perature phosphorescence properties of several tetrahydrocarbazole, carbazole, and 1,4-benzodiazepine classes. The use of sensitized R T P from so lutions for detection in continuous flow and chromatographic systems was developed by Donkerbroek et al. (59). Biacetyl was used as the acceptor molecule and analytical data were re ported for polyhalogenated naphtha lenes and biphenyls. They paid partic ular attention to the eluent vessel and the injection system for the continu ous flow system. Deoxygenation of the eluent was essential for high sensitivi ty. The limits of detection ranged from 10~ 9 to 10~ 8 M for the halogenated naphthalenes and biphenyls with the continuous flow system. It was also demonstrated that solution-sensi tized R T P could be applied success fully for detection in liquid chroma tography with a reversed-phase sys tem. Nanogram amounts of several compounds were detected. Back ground noise due to scattering and to fluorescent impurities was minimized because of the relatively long emission wavelength of the acceptor. Future de velopments of new acceptor systems should extend the applicability of sen sitized R T P from liquids. Fortier and Eastwood (60) used low-temperature luminescence for the identification of fuel oils. Both fluo rescence and phosphorescence spectra were obtained, and a considerable in crease in spectral structure was ob tained at 77 K. Corfield et al. (61) spe cifically considered the application of low-temperature phosphorescence to crude oil identification. They evalu ated conventional phosphorimetry, synchronous excitation phosphorime try, and total phosphorescence con tour diagrams. They concluded that conventional phosphorimetry was of limited use in oil spill identification because of the lack of structural fea tures in the emission spectra. With synchronous excitation phosphorime try, increased detail could be obtained
to support information obtained by fluorescence methods. Using two-di mensional representations of the three-dimensional dependence of phosphorescence intensity on excita tion and emission wavelengths, total phosphorescence contour diagrams were obtained as shown in Figure 6. The contour diagrams allowed differ entiation between eight oils studied either by superposition or by subtrac tion methods. This approach gave the most detailed information from the phosphorescence techniques studied. In general, they considered phospho rescence information as complementa ry to fluorescence information. Conclusion A variety of modern instruments and instrumental systems are used for phosphorescence analytical work. Capabilities of these instruments and systems range from simple collection of phosphorescence data to sophisti cated data processing and handling. Some possible future instrumental de velopments were mentioned earlier. Because many of these instruments are readily available or can be con structed from existing parts, phosphorimetry will continue to provide excel lent sensitivity and selectivity in or ganic trace analysis. Phosphorescence and fluorescence are complementary and each can be used in a variety of analytical situa tions. However, the combined use of fluorescence and phosphorescence in the analysis of mixtures will give more information than either can separate ly. With the advent of RTP, one should see greater combined use of phosphorescence and fluorescence in mixture analysis. Solid-surface, micelle-stabilized, and solution-sensitized R T P are im portant new developments in phosphorimetry. A better understanding of the chemical and physical interactions of these new analytical approaches is needed to develop their full sensitivity and selectivity. As new insights emerge, these techniques will find much greater use in organic trace analysis. References (1) Lewis, G. N.; Kasha, M. J. J. Am. Chem. Soc. 1944, 66, 2100. (2) Keirs, R. J.; Britt, R. D.; Wentworth, W. E. Anal. Chem. 1957,29, 202. (3) Freed, S.; Salmre, W. Science 1958, 128, 1341. (4) Parker, C. Α.; Hatchard, C. G. Analyst 1962,87, 664. (5) Winefordner, J. D.; Latz, H. W. Anal. Chem. 1963,35,1517. (6) Birks, J. B. "Photophysics of Aromatic Molecules"; Wiley: New York, 1970. (7) Winefordner, J. D.; Schulman, S. G.; O'Haver, T. C. "Luminescence Spec trometry in Analytical Chemistry"; Wiley: New York, 1972. (8) Parker, R. T.; Freedlander, R. S.; Dun-
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lap, R. B. Anal. Chim. Acta 1980,119, 189; 1980,120, 1. (9) Cline Love, L. J.; Skrilec, M.; Habarta, J. G. Anal. Chem. 1980,52, 754. (10) Donkerbroek, J. J.; Gooijer, C; Velthorst, N. H.; Frei, R. W. Anal. Chem. 1982 54 891 (11) Ward, J. L.; Walden, G. L.; Wineford ner, J. D. Talanta 1981,28, 201. (12) Ward, J. L.; Bateh, R. P.; Wineford ner, J. D. Appl. Spectrosc. 1980, 34,15. (13) Ward, J. L.; Walden, G. L.; Bateh, R. P.; Winefordner, J. D. Appl. Spec trosc. 1980, 34, 348. (14) Roth, M. J. Chromatogr. 1967,30, 276. (15) Schulman, E. M.; Walling, C. Science 1972,178,53. (16) Schulman, E. M.; Walling, C. J. Phys. Chem. 1973,77,902. (17) Paynter, R. Α.; Wellons, S. L.; Wine fordner, J. D. Anal. Chem. 1974, 46, 736. (18) Lue-Yen Bower, E.; Ward, J. L.; Wal den, G.; Winefordner, J. D. Talanta 1980,27, 380. (19) Hurtubise, R. J. "Solid Surface Lumi nescence Analysis: Theory, Instrumenta tion, Applications"; Marcel Dekker: New York, 1981; Chapters 3, 5, 7. (20) Schulman, E. M.; Parker, R. T. J. Phys. Chem. 1977, 81,1932. (21) Von Wandruszka, R.M.A.; Hurtu bise, R. J. Anal. Chem. 1977, 49, 2164. (22) Niday, G. J.; Seybold, P. G. Anal. Chem. 1978,50,1577. (23) Hurtubise, R. J.; Smith, G. A. Anal. Chim. Acta 1982,139, 315. (24) Lue-Yen Bower, E.; Winefordner, J. D. Anal. Chim. Acta 1978,102,1. (25) Skrilec, M.; Cline Love, L. J. Anal. Chem. 1980,52, 1559. (26) Donkerbroek, J. J.; Elzas, J. J.; Gooi jer, C; Frei, R. W.; Velthorst, N. H. Ta lanta 1981,28,717. (27) Guilbault, G. G. "Practical Fluores cence: Theory, Methods, and Tech niques"; Marcel Dekker: New York, 1973. (28) Cline Love, L. J.; Upton, L. M.; Ritter, A. W. Anal. Chem. 1978,50, 2059. (29) Ford, C. D.; Hurtubise, R. J. Anal. Chem. 1980,52,656. (30) Vo-Dinh, T.; Walden, G. L.; Wine fordner, J. D. Anal. Chem. 1977, 49, 1126. (31) Lue-Yen Bower, E.; Winefordner, J. D. Appl. Spectrosc. 1979, 33, 9. (32) Walden, G. L.; Winefordner, J. D. Appl. Spectrosc. 1979,33, 166. (33) Reference 19, Chapter 3. (34) Fisher, R. P.; Winefordner, J. D. Anal. Chem. 1972,44,948. (35) Harbaugh, K. F.; O'Donnell, C. M.; Winefordner, J. D. Anal. Chem. 1974, 46,1206. (36) Boutilier, G. D.; Winefordner, J. D. Anal. Chem. 1979,51, 1384. (37) Boutilier, G. D.; Winefordner, J. D. Anal. Chem. 1979,51,1391. (38) Wilson, R. M.; Miller, T. L. Anal. Chem. 1975,47, 256. (39) Goeringer, D. E.; Pardue, H. L. Anal. Chem. 1979,51,1054. (40) Mousa, J. J.; Winefordner, J. D. Anal. Chem. 1974,46,1195. (41) Lue Yen, E.; Winefordner, J. D. Anal. Chem. 1977,49,1262. (42) Ho, C.-N.; Warner, I. M. Trends. Anal. Chem. 1982,1 (7), 159. (43) Johnson, D. W.; Callis, J. B.; Chris tian, G. D. Anal. Chem. 1977,49, 747 A. (44) Warner, I. M.; Christian, G. D.; Da vidson, E. R.; Callis, J. B. Anal. Chem. 1977,49, 564. (45) Fogarty, M. P.; Warner, I. M. Anal. Chem. 1981,53,259. (46) Vo-Dinh, T.; Gammage, R. B. Anal. Chem. 1978,50, 2054. (47) Vo-Dinh, T. Appl. Spectrosc. 1982, 36, 576. (continued on p. 680 A)
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(48) Inman, E. L.; Winefordner, J. D. Anal. Chim. Acta 1979,141,241. (49) Vo-Dinh, T.; Gammage, R. B. Anal. Chim. Acta 1979,107, 261. (50) Warren, M. W.; Avery, J. P. Malmstadt, H. V. Anal. Chem. 1982,54, 1853. (51) Von Wandruszka, R.M.A.; Hurtubise, R. J. Anal. Chem. 1976, 48, 1784. (52) Ford, C. D.; Hurtubise, R. J. Anal. Lett. 1980,13 (A6), 485. (53) Vo-Dinh, T.; Gammage, R. B.; Mar tinez, P. R. Anal. Chim. Acta 1980,118, 313. (54) Vo-Dinh, T.; Martinez, P. R. Anal. Chim. Acta 1981,125, 13. (55) Weinberger, R.; Yarmchuk, P.; Cline Love, L. J. Anal. Chem. 1982, 54,1552. (56) O'Donnell, C. M.; Winefordner, J. D. Clin. Chem. 1975, 21, 285. (57) Gifford, L. Α.; Miller, J. N.; Phillipps, D. L.; Burns, D. T.; Bridges, J. W. Anal. Chem. 1975, 47, 1699. (58) DeSilva, J.A.F.; Strojny, N.; Stika, K. Anal. Chem. 1976, 48,144. (59) Donkerbroek, J. J.; Van Eikema Hommes, N.J.R.; Gooijer, C ; Velthorst, N. H.; Frei, R. W. Chromatographia 1982,15, 218. (60) Fortier, S. H.; Eastwood, D. Anal. Chem. 1978,50,334. (61) Corfield, M. M.; Hawkins, H. L.; John, P.; Soutar, I. Analyst 1981,106, 188.
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R. J. Hurtubise studied at Ohio Uni versity, where he received a PhD in analytical chemistry. After working at Rockhurst College and Pfizer Inc., he accepted a faculty position at the University of Wyoming, where he is now an associate professor of chemis try. His current research interests focus on the physical and chemical interactions in solid-surface lumines cence analysis and the application of this luminescence approach to organ ic trace analysis. In addition, he is in vestigating solute/mobile phase and solute/stationary phase interactions in LC. The results are used in pre dicting retention and designing sepa ration schemes for the isolation of nu merous components in coal liquid samples. The isolated components are being characterized by several spectral techniques.
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