and encouragement, James R. Leue of the Paxton Woods Glass Shop for his consultation and work on the modification of the quartz sample ladle, and Mrs. Ellen White of the Control Systems Division for her statistical advice.
Table IV shows results from atmospheric samples collected over various time periods in Secaucus, N.J., during November 1969 and January and February 1970. The significant concentrations and percentages of C-H-N observed indicate the importance of this analysis technique to today’s air pollution chemists.
RECEIVED for review May 12, 1972. Accepted November 17, 1972. Mention of commercial products or company names does not constitute endorsement by the Environmental Protection Agency.
ACKNOWLEDGMENT The author wishes to thank Jack Wagnian of the Source Emission Measurement Methods Branch for his support
Analysis of Halogenated Biphenyls by Pulsed Source-Time Resolved Phosphorimetry C. M. O’Donnell,’ K. F. Harbaugh, R. P. Fisher,2 and J. D. Winefordner3 Department of Chemistry, Unicersity of Florida, Gainescille, Fla. 32601 ~~
PULSEDSOURCE, TIME RESOLVED PHOSPHORIMETRY was introduced by O’Haver and Winefordner ( I ) and discussed by Winefordner ( 2 ) . Recently, Fisher and Winefordner (3) have described a pulsed source phosphorimeter, have given the advantages of their pulsed phosphorimeter as compared to conventional phosphorimeters, and have applied their pulsed phosphorimeter to the time resolution of several synthetic binary mixtures and a ternary mixture of spectrallysimilar phosphors. In the present manuscript, the utility of pulsed source, time resolved phosphorimetry for quantitative analysis of several mixtures of halogenated biphenyls is demonstrated. The halogenated biphenyls have nearly identical phosphorescence emission spectra when measured with a conventional phosphorimeter but widely different phosphorescence lifetimes, i.e., 5 to 500 msec. The pulsed source, time resolved phosphorimeter used in the present studies differed from the one used by Fisher and Winefordner ( 4 ) in two major respects: a rotating sample cell ( 4 , 5 ) was used rather than the previous stationary cell; and a more intense flash lamp source was used. EXPERIMENTAL Instrumentation. The instrument used was identical to the one described by Fisher and Winefordner (3) except for the following changes: (i) a Novdtron 599 CR flash lamp powered by a Model 457 Micropulser (Xenon Corp., Medford, Mass. 02155) was used instead of the previous lower power flash lamp; (ii) a Wavetek Model 110 function generator (Wavetek, San Diego, Calif. 92123) was used to provide an On leave: Department of Chemistry, Colorado State University, Fort Collins. Colo. 80521. Present location, National Council for Air and Stream Improvement, Inc., Gainesville, Fla. 32601. Author to whom reprint requests should be sent. (1) T. C. O’Haver and J. D. Winefordner, ANAL.CHEM.,38, 602
(1 966). (2) J. D. Winefordner, Accowits Cliern. Res., 2, 361 (1969). (3) R. P. Fisher and J. D. Winefordner, ANAL.CHEW,44, 948 (1972). (4) R. J. Lukasiewicz. P. A . Rozynes, L. B. Sanders, and J. D. Winefordner, ibid., p 237. (5) R. J . Lukasiewicz. J. J. Mousa. and J. D. Winefordner, ibid., p 1339.
~
Table I. Phosphorescence Characteristics of Selected Halogenated Biphenyls
a
Halogenated biphenyl
Peak phosphorescence emission wavelength,a nm
Phosphorescence lifetime? msec
2-Chlorobiphenyl 3-Chlorobiphenyl 4-Chlorob~phenyl 2-Bromobiphenyl 3-Bromobiphenyl 4-Bromobiphenyl 4,4’-Dibromobiphenyl 2-Iodobiphenyl 4-Iodobiphenyl
465 480 477 475 480 480 485 490 480
170 1300 570 3 3 58 17 12 3 0 3 2
Solvent:
ethyl alcohol.
* Relative errors in lifetimes are less than 10%
external trigger for the source power supply and for the Biomac Model 1000 signal averager (Biomation, Palo Alto, Calif. 94303); and (iii) a rotating sample cell assembly (sample cell was a quartz tube 3 mm i.d. X 5 mm 0.d. X 22.5 cm long) as described by Lukasiewicz et al. ( 4 , 5 ) was used rather than the conventional stationary cell systems. Reagents. The halogenated biphenyls (obtained from Pfaltz and Bauer, Flushing, N.Y. 11368) used for the present studies and their phosphorescence characteristics are given in Table I. Ethyl alcohol (U.S.I.) was used as the solvent in all studies. The halogenated biphenyls were used as received from the supplier; semilogarithmic plots of phosphorescence signal cs. time after termination of excitation were linear over two decades of phosphorescence signal indicating sufficient purity (3). Procedure. The procedure used was identical to the one described by Fisher and Winefordner (3)except for the following changes. Prior to recording the phosphorescence decay curve, suitable delay time was set on the signal averager to minimize measurement of source scatter and a suitable sweep time was set to enable measurement of the desired phosphorescent species. The sweep time was chosen to temporally compress the shorter-lived species with respect t o the longestlived phosphor ; the resulting phosphorescence signal of the ANALYTICAL CHEMISTRY, VOL. 45, NO. 3, MARCH 1973
609
WAVELENGTH (nrn)
Figure 1. Phosphorescence spectra of 4-chlorobiphenyl (Curve A ) , 4-bromobiphenyl (Curve B), and 4-iodobiphenyl (Curve C). All halogenated biphenyls in ethyl alcohol solvent
Table 11. Analysis of Mixtures of Halogenated Biphenyls by Pulsed Source, Time Resolved Phosphorimetry Mixture 4-Chlorobiphenyl 4-Bromobiphenyl 4-Iodobiphenyl 2-Chlorobiphenyl 4-Chlorobiphenyl
Composition of mixture, molesil Present Found 2.0 X 10-5 1 . 9 X 10-5 5.0 X 10+ 4.8 X
x
5.0 X
4.3
3 . 7 X 10-5 2.0 X loV5
3 . 9 X 10-5
1.8 X 10-5
Error 5.0
4.0 14. 5.4 10.
longest-lived species extrapolated to zero delay time was subtracted from the sum of the two longest-lived phosphors t o determine the phosphorescence signal of the intermediate lived species. This same procedure was then repeated again if necessary, e.g., with a ternary mixture or greater number component mixture.
RESULTS AND DISCUSSION The phosphorescence emission spectra of 4-chlorobiphenyl, 4-bromobiphenyl, and 4-iodobiphenyl are given in Figure 1. It is apparent that a quantitative analysis of a mixture of these three halogenated biphenyls would be difficult by conventional phosphorimetry because of the severe overlap of their phosphorescence emission (and excitation) spectra. From the phosphorescence lifetime data in Table I, it seems evident that time resolved phosphorimetry should be useful for the analysis of the 4-halobiphenyl mixture. The phosphorimetric limits of detection for the three 4-halobiphenyls are: 0.001 pg (4.3 X 10-l2 mole) for 4-bromobiphenyl; 0.001 pg (3.6 X lo-'* mole) for 4-iodobiphenyl; and 0.01 pg 610
ANALYTICAL CHEM!STRY, VOL. 45, NO. 3, MARCH 1973
(5.3 x 10-11 mole) for 4-chlorobiphenyl (the cell volume was about 200 pl). The detection limit was determined as that concentration of halogenated biphenyls resulting in a phosphorescence signal equal to 10% of the ethanolic background. In a recent paper, Dreeskamp et 01. (6) have also reported spectral data for 2-, 3-, and 4-monochlorobiphenyls; these workers found similar phosphorescence lifetimes and quantum yields for 2- and 4-chlorobiphenyl as in Table I. The discrepancy between the lifetimes and detection limit of the 3-chlorobiphenyl species as compared to the other two chlorobiphenyls (see Table I and above discussion) may be a result of preferential quenching of 3-chlorobiphenyl by some impurity. Analytical curves (plots of phosphorescence signal 1's. concentration of the designated 4-halobiphenyl) were linear within +3% (maximum deviation from linearity a t high concentrations) from the limit of detection to a concentration at least 4 decades above the limit of detection for each halogenated biphenyl. In Figure 2, three decay curves (semilogarithmic plots of phosphorescence signal cs. time after termination of source radiation) are presented; the importance of signal averager sweep time upon the resolution of the three halogenated biphenyls is evident (note the different scales for the ordinate and abscissa). For each of the decay curves, a delay time of 0.32 msec was used. The quantitative results for the ternary mixture of halogenated biphenyls are given in Table 11; the maximum absolute error in concentration was 5 % or less for the 4-chlorobiphenyl and the 4-bromobiphenyl and 14 % for the shortest-lived species, 4-iodobiphenyl. A second mixture consisting of 2-chlorobiphenyl and 4chlorobiphenyl (detection limit of 0.01 pg for both 2-chloro-
( 6 ) H. Dreeskamp, 0. Hutzinger, and M. Zander. Z. hiht~rforscl?. B , 27, 756 (1972).
Figure 2. Phosphorescence decay curve plots of logarithm of the phosphorescence signal GS. time after termination of excitation for a mixture of 4-chlorobiphenyl (2.0 X 10-6M), 4-bromobiphenyl (5.0 X 10-6M), and 4-iodobiphenyl (5.0 X 10-6M). Ethanol was the solvent Key: Sweep time of 20 msec A Sweep time of 80 msec 0 Sweep time of 1280 msec
no attempt was made to also determine 3-chlorobiphenyl because of its low phosphorescence quantum yield (therefore, poor phosphorimetric limits of detection, about 1000-fold worse than the 2-chloro and 4-chloro species). Although the structural difference between 2-chlorobiphenyl and 4chlorobiphenyl is small and the phosphorescence spectra (also absorption and fluorescence spectra) are almost identical, the phosphorescence lifetimes and, therefore, the phosphorescence decay curves are quite different. This is another excellent example of a mixture analysis which would be difficult to perform by normal spectroscopic measurements but not by pulsed source, time resolved phosphorimetry. As long as the phosphorescence lifetime ratio of any two species is two or greater, phosphoroscopic resolution is possible via time resolved phosphorimetry. In conclusion, pulsed source, time resolved phosphorimetry is a useful method for the analysis of structurally and therefore spectrally similar molecules. Not only is it possible to obtain quantitative information, but also it should be possible to qualitatively identify some species with the assistance of the species phosphorescence lifetimes. For very complex mixtures, a simple thin layer or gas chromatographic separation prior to analysis may also be needed, but overall, the time for analysis of a multicomponent mixture should be considerably reduced as compared to methods previously used. It should also be possible to measure longer-lived phosphorescence species, e.g., species with lifetimes exceeding 1 sec, in a mixture also containing shortlived species as well as other long-lived species. Such studies are currently in progress.
biphenyl as well as 4-chlorobiphenyl) was similarly measured by pulsed source, time resolved phosphorimetry, and the results are also given in Table I1 errors of 5.4z and l o % , respectively). Again, this mixture cannot be readily measured by conventional phosphorimetry because of the similarity of the phosphorescence spectra. It should be pointed out that
RECEIVED for review July 25, 1972. Accepted November 16, 1972. Research was carried out as part of a study on the phosphorimetric analysis of drugs in blood and urine, supported by a U S . Public Health Service Grant (GM-11373-10).
L
l
I
100
2
200
4
3
300
400
5
500
TIME ( r n s e c . )
(z
Novel Wet-Digestion Procedure for Trace-Metal Analysis of Coal by Atomic Absorption A. M. Hartstein, R . W. Freedman, and D. W. Platter Pittsburgh Mining and Safety Research Center, Bureau of Mines, US.Department of the Interior, Pittsburgh, Pa.
COALWORKERS’ PNEUMOCONIOSIS, its causes and cure, is the subject of intensive studies by different laboratories throughout the world. This form of pneumoconiosis is believed to be caused by the inhalation and retention of respirable coalmine dust (
