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Anal. Chem. 1982, 5 4 , 1570-1572
(8) Husain, S.;Kunzelmann, P.; Schildknecht, H. J . Chromafogr. 1977, 737, 53-60. (9) Schomburg, G.;Husmann, H.;Weeke, F. J. Chromafogr. 1975, 7f2, 205-217. (IO) Brooks, V. T. Chem. Ind. (London) 1959, 1317-1318. (11) Guenther, F. R.; Parris, R. M.; Chesier, S. N.; Hiipert, L. R. J . Chromafogr. 1081, 207, 256-261. (12) Grob, K., Jr.; Grob, K. J . Chromatogr. 1977, 740, 257-259. (13) Janak, J.; Komers, R. “Gas Chromatography 1958”;Desty, D. H., Ed.; Butterworths: London, 1958;Chapter 26. (14) Ono, A. Chromatographla 1080, 73, 574-575. (15) Ettre, L. S.; Obermiller, E. I n “Encyclopedia of Industrial Chemlcai Analysis”; Interscience: New York, 1973;Vol. 17. (16) Averill, W. Perkln-Elmer Qas Chromatography Applications, Application No. GC-DS-001; Perkln-Elmer Corporation: Norwaik, CT, 1963. (17) Hrivnak, J.; Beska, E. J. Chromafogr. 1074. 8 9 , 309. (18) Macak, J.; Buryan, P.; Hrivnak, J. J. Chromafogr. 1974, 89, 309-317. (19) Buryan, P.; Macak, J.; Hrivnak, J. J . Chromafogr. 1077, 737, 425-430. (20)Buryan, P.; Macak, J. J . Chromatogr. 1977, 739, 69-75. (21)Buryan, P.; Macak, J. J . Chromafogr. 1078, 750, 246-249. (22) Verzele, M.; Sandra, P. J . Chromatogr. 1078, 758, 111-119. (23) Sandra, P.; Verzele, M.; Verstappe, M.; Verzeie, J. J . High Resoluf. Chromafogr. Chromafogr. Commun. 1979, 2 , 288-292. (24) Haken, J. K. Adv. Chromatogr. 1076, 74, 367-407. (25) Karger, B. L. Anal. Chem. 1967, 39 (E),24 A-50 A.
(26) James, A. T.; Martin, A. J. P. Blochem. J. 1952, 50, 679-690. (27) Van Den Dool, H.; Kratz, Dec. P. J . Chromatogr. 1983, 7 7 , 463-471. (28) Laub. R. J. Anal. Chem. 1080, 52, 1219-1221. (29) Lee, M. L.; Vassiiaros, D. L.; White, C. M.; Novotny. M. Anal. Chem. 1979, 57, 768-774. (30) Majlat, P.; Erdos, 2.; Tackacs, J. J . Chromatogr. 1074, 97, 89. (31) Dandeneau, R. D.; Zerenner, E. H. J . High Resolut. Chromafogr. Chromatogr. Commun. 1979, 2 , 351-356. (32) Hoshika, Y. J . Chromatogr. 1977, 744, 181-189. (33) Baker, R. A.; Malo, B. A. Environ. Sci. Techno/. 1087, 7 , 997-1007. (34) Evans, M. B.; Smith, J. F. J . Chromafogr. 1988, 36, 489-503. (35) Karger, B. L.; Elmehrik, Y.; Andrade, W. J. Chromafogr. Sci. 1989, 7 , 209-217. (36) Karger, B. L.; Elmehrik, Y.; Stern, R. L. Anal. Chem. 1988, 4 0 , 1227-1232. (37) Jordan, T. E. “Vapor Pressures of Organic Compounds”; Interscience: New York, 1954. (38) Connor, T. M.; McLauchlan, K. A. J. Phys. Chem. 1085, 6 9 , 1888-1893. (39) Verzele, M.; Sandra, P.; Verzele, J. Int. Lab., submltted.
RECEIVED for review January 27,1982. Accepted April 5,1982. N.C.L. acknowledges support by Department of Energy Contract to Duquesne University, No. DE-AC-22-80PC30252.
Determination of Phenols in a Coal Liquefaction Product by Gas Chromatography and Combined Gas ChromatographyIMass Spectrometry Curt M. White*’ and Norman C. Li Department of Chemlstty, Duquesne Unlversiw, Pittsburgh, Pennsylvania
152 19
The phenolic fraction of a SRC-I1 middle distillate was Isolated and the individual phenolic constituents further separated and Identified by using gas chromatography and combined gas chromatography/mass spectrometry. This complex mixture of phenols was separated with a high-resolution fused-silica capillary column wali-coated with Superox-2OM. Identification of 29 compounds was possible. All compounds except one were Identified by using two identification parameters: (1) cochromatography with authentic standards and, (2) matching mass spectra. Ail major and most minor constituents have been identlfled.
gasification products has been performed by Karr et al. (1-3), Pichler et al. (4-6), and Buryan and Macak (7-11). Although the phenolic materials in coal carbonization products and gasification products have been extensively characterized, little detailed information is available on the exact nature of phenols in direct coal liquefaction products. Several methods have been developed for separating phenolic fractions from coal liquefaction products and subsequent analysis of the resulting fractions by bulk characterization techniques such as nuclear magnetic resonance and/or highresolution mass spectrometry (12-16). Schabron, Hurtubise, and Silver have described analyses of phenol-rich fractions from coal liquefaction products using high-performanceliquid chromatography, chemical spot tests, ultraviolet absorption spectroscopy, and fluorescence spectroscopy (17). After considerable effort, only four compounds could be positively identified, phenol and 2-, 3-, and 4-methylphenol. Guenther and co-workers have examined a solvent-refined coal (SRC) for phenolic materials using GC/MS, and were able to positively identify seven compounds-phenol, the three methylphenols, and three dimethylphenols (18). Similarly, Zingaro et al. have examined the phenolic contents of coal liquefaction products but were able to identify only phenol and the methylphenols (19). Lastly, White and Schmidt positively identified 12 phenolic compounds in the byproduct waters from two coal liquefaction processes using gas-solid chromatography and GC/MS (20). Due to the dramatic increase in the qualitative analytical chemistry of fuels, it may be desirable, for the purposes of this paper, to define the meaning of “positive identification” of compounds. For these purposes, a positively identified compound is one which has been identified by a minimum of two
The analysis of phenols in coal and coal-derived products has received considerable attention. The phenolic products from the carbonization and gasification of coal have been extensively characterized using a wide variety of analytical methods and techniques. The literature contains a plethora of publications on the characterization of phenolic materials in these products, the most reliable characterizations being performed with gas chromatography and combined gas chromatography/mass spectrometry (GC/MS). Indeed, the best gas chromatographic methods available for the analysis of complex mixtures of phenols have been developed by chromatographers interested in separating coal-derived phenolic mixtures. Some of the most extensive work on the detailed characterizations of phenols in coal carbonization and Author to whom correspondence should be addressed Analytical Chemistry Division, Pittsburgh Energy Technology Center, P.O. Box 10940, Pittsburgh, PA 15236. 0003-2700/82/0354-1570$01.25/0
0 1982 American Chemical Society
ANALYTICAL CHEMISTRY, VOL. 54, NO. 9, AUGUST 1982
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Table I. Identification of Phenols in an SRC-I1Middle Distillate, See Figure 1 peak no.
Phenol fraction from SRC
1
I
0
10
20
,
30
,
1
I
40
50
60
I 175
195
1
,
70 72
TIME, minutes
I
75
I 95
I 115
L
I
135 I55 TEMPERATURE. 'C
I
I
)
215pO
Flgure 1. Hlgh-resolution gas chromatographic proflle of the phenol fraction from a SRC-I1 middle dlstiilate. See Table I for compound identifications. See Experimental Section for chromatographic con-
ditions. independent analytical l;ools, Le., cochromatography with authentic standards and mass spectrometry. Thus, it is possible to assign a name to such a compound for which only one structure can be drawn, and in all probability, this is the correct structure. From the above discussion, it is evident that analytical methods for the positive identification of phenolic compounds in complex mixtures found in coal liquefaction products are not well developed. Our knowledge concerning the exact identities of the phenolic constituents in coal liquefaction products is quite small. 'This is unfortunate because of the important role phenols ]play in coal liquefaction chemistry. Phenols have been implicated as playing a role in determining the quality of coal liquefaction recycle solvents (21). Substantial evidence exists that phenols are involved during aging reactions of coal liquefaction products (22, 23). Further, phenols may exhibit a degree of toxicity which may be related to their structures. Thus, it is necessary to distinguish and positively identify the various phenolic compounds present in coal liquefaction products in order to monitor the workplace atmospheres of coal liquefaction plants. For these reasons, it was decided to characlsrize, in as much detail as possible, the phenolic compounds iin a SRC-I1 middle distillate. Previous to this undertaking, the gas chromatographic retention characteristics of a variety of phenolic compounds were determined on fused silica capillary columns coated with Superox-20M (24).
EXPERIMENTAL SECTION A SRC-I1middle distillate boiling from 453 to 665 K (180 to 392 "C) was solvent separated into oils and asphaltenes using n-pentane to yield 99.3% ]pentane soluble oils (25). Acidic componenta were isolated from the oils using an anion exchange resin eluted with benzene, methanol/C02, and THF/HC02H. The majority of phenols were eluted with methanol/COz. Details of the method are described elsewhere (12). The phenol fraction was diluted with methylene chloride and subjected to high-resolution gas chromatographicanalysis employing an HP-5840 gas chromatograph, a 30 m X 0.20 mm fused-silicacapillary column coated with a 0.10-pm film of Superox-SOM,and a flame ionization detector. Helium carrier gas was purified by passing it through an oxygen absorption trap. The flow rate was 1.75 mL/min at 75 "C and had a linear velocity of 55 cm/s. The column was temperature programmed from 348 K to 493 K at 2 K/min. The split ratio was 300:l. The resulting chromatographicpeaks were identified by cochromatography with authentic standards. Identification of the rendting peaks was corroborated independently by mass spectrometry using an HP-5985 GC/MS employing the same column and chromatographic conditions as described above. The fused-silicacolumn was interfaced directly to the ion source of the maso spectrometer. An ionization potential
2 3 4 5 6 7 8 9 10 11
12 13 14 15 16 17
compounda 2,6-dimethylphenol phenol 2-methylphenol 2,5-dimethylphenol and 4-methylphenol 2,4-dimethyphenol 3-methylphenol 2-isopropylphenol 2,3-dimethylphenol 2-n-propylphenol 3,5-dimethylphenol and 4-ethylphenol 3-ethylphenol 3,4-dimethylphenol 1 4-isopropylphenol 3-isopropylphenol and 2,3,S-trimethylphenol 4-n-propylphenol 3-n-propylphenol 4-sec-butylphenol 4-indanol 5-indanol 6-methyl-4-indanol 7-methyl-4-indanol 5,6,7,8-tetrahydro-1-naphthol 7-methyl-5-indanol 2-phenylphenol 5,6,7,8-tetrahydro-2-naphthol 1-naphthol 2-naphthol
18 19 20 21 22 23 24 25 26 27 28 3-phen ylphenol 29 4-phenylphenol a Each compound except 3-n-propylphenol has been positively identified based on two identification parameters: matching retention times with authentic standards during cochromatography, and matching mass spectrum. ~
of 70 eV, scan speed of 1.2 s/scan and an electron multiplier voltage of 2200 V were employed.
RESULTS AND DISCUSSION The high-resolution gas chromatographic profile of the phenol fraction of the SRC-I1 middle distillate appears in Figure 1, while the numbered chromatographic peaks are identified in Table I. Note the symmetrical elution (nontailing) of each constituent. All compounds, except 3-npropylphenol have been positively identified based on two identification parameters, i.e., matching gas chromatographic retention characteristics as determined by cochromatography with authentic standards and matching mass spectra. The use of these combined techniques permits the positive identification of many minor and trace phenolic constituents. Although 3-n-propylphenol was not identified by cochromatography, because we had no standard, its identification is considered reliable. The chromatographic peak identified as 3-n-propylphenol elutes just after 4-n-propylphenol. This is exactly where it should elute based on studies of other standards (24). Further, this peak had the correct mass spectrum. As can be seen from the chromatographic profile, the components in highest concentration are phenol, methyl phenols, and dimethylphenols. Many of the trace components eluting after 5-indanol could not be positively identified due to a lack of standards. This emphasizes the need for the synthesis of pure phenolic standards in this boiling range. Although mass spectra were acquired on the components that are not identified, and thus structural information is available, they have not been identified in this paper because mass spectral data by itself cannot, in general, be used to positively identify compounds. Although no rigorous quantitative data are presented concerning the concentrations of the individual phenolic
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Anal. Chem. 1982, 54. 1572-1575
compounds in the original SRC-11, the development of this gas chromatographic methodology establishes the means to quantitate these individual phenols in the SRC-I1 matrix. It is our belief that reliable quantitative data on individual compounds will be best made in the unseparated coal liquid, because of losses involved during solvent removal and incomplete and variable recovery of sample from chromatographic stationary phases. It should be possible to quantitate these phenolic compounds in the unseparated raw coal liquefaction distillates by employing the GC/MS technique of selected ion monitoring (SIM) and the method of standard additions. This eliminates problems of incomplete recovery during the solvent separation and chemical class fractionation steps. Experiments are currently in progress to attempt this. The use of high-resolution gas chromatography employing fused-silica columns coated with Superox-20M and of combined GC/MS with the same column has led to the detailed characterization of phenolic constituents and identification of 29 phenols from a SRC-I1 middle distillate. These techniques, combined with a knowledge of the retention characteristics of phenols on Superox-ZOM,are useful for the separation and positive identification of individual phenolic compounds present in complex mixtures. The use of this stationary phase should find wide application in separation of phenolic mixtures from a variety of sources. ACKNOWLEDGMENT We wish to acknowledge Takao Hara for fractionating the coal liquid into functional groups and thus providing the phenol fraction. Furthermore, helpful discussions were provided by Dennis Finseth, Richard Sprecher, and Frank Schweighardt. LITERATURE CITED (1) Karr, C., Jr.; Brown, P. M.; Estep, P. A,; Humphrey, G. L. Anal. Chem. 1958, 30, 1413-1416.
(2) Karr, C., Jr.; Brown, P. M.; Estep, P. A.; Humphrey, G. L. fuel 1958, 37, 227-235. (3) Karr, C., Jr.; Estep, P. A.; Hirst, L. L. Anal. Chem. 1960, 32, 463-475. (4) Pihler, H.; Hennenberger, P.; Schwarz, 0. 6f8nnSt.-Chem. 1988, 49, 175-186. ( 5 ) Plchler, H.; Schwarz, G. Bfennst.-Chem. 1969, 50, 72-78. (6) Plchler, H.; Herlan, A. Erdoel Kohle, Erdgas, P8tfOChem. 8rennst.Chem. 1973, 26, 401-407. (7) Buryan, P.; Macak, J.; Nabivach, V. M. J. Chromatogr. 1878, 148, 203-210. ( 8 ) Macak, J.; Buryan, P. Chem. Lis@ 1875, 69, 457-518. (9) Buryan, P.; Macak, J. Sb. Vys. Sk, Chem.-Techno/. Pram, Technol. faliv. 1977. 0 3 4 , 39-84. (IO) Macak, J.; Buryan, P.; Nabivach, V. M. Koks Khlm. 1979, 3 , 29-36. (11) Buryan, P.; Macak, J.; Zachar, P.; Kos, J. Ropa Uhli8 1978, 18, 205-217. (12) Jewell, D. M.;Weber, J. H.; Bunger, J. W.; Plancher, H.;Latham, D. R. Anal. Chem. 1872. 4 4 , 1391-1395. (13) Schiller, J. E.; Mathiasson, D. R. Anal. Chem. 1977, 4 9 , 1225-1228. (14) Coleman, H. J.; Dooley, J. E.; Hirsch, D. E.; Thompson, C. J. Anal. Chem. 1873, 45, 1724-1737. (15) Farcaslu. M. fuel 1977. 56, 9-14. (16) Bartle, K. D.; Matthews. R. S.; Stadelhofer, J. Appl. Spectrosc. 1980, 34, 615-618. (17) Schalbron, J. F.; Hurtubise, R. J.; Silver, H. F. Anal. Chem. 1979, 51, 1426-1433. (18) Guenther, F. R.; Parris, R. M.; Cheder, S. N.; Hilpert, L. R. J. Chromatwf. 1981, 207, 256-261. (19) Zingaro, R. A.; Phillp, C. V.; Anthony, R. G.; Vindiola, A. fuel Process. Technol. 1981, 4 , 169-177. (20) Whlte, C. M.; Schmidt, C. E. frepr. Pap.-Am. Chem. SOC.,Dlv. Fuel Chem. 1978, 2 3 , 134-143. (21) EPRI ProJect Report 410-1; Mobll Research and Development Corp., 1979. (22) Brinkman, D. W.; Whlsman, M. L.; Bowden. J. N. BETClRI 76/23, March 1979. (23) Hara, T.; Jones, L.; LI, N.C.; Tewarl, K. C. fuel 1981, 60, 1143-1148. (24) Whlte, C. M.; Li, N. C. Anal. Chem., preceding paper In this Issue. (25) Tewari, K. C.; Egan, K. M.; Li, N. C. Fuel 1978, 57, 712-716.
RECEIVED for review February 22, 1982. Accepted April 5, 1982. N.C.L. acknowledges support by the Department of Energy Contract to Duquesne University, No. DE-AC2280PC30252.
Determination of Airborne 1,6=Hexamethylene Diisocyanate by Gas Chromatography G. G. Esposlto* and T. W. Dolzlne U.S. Army Environmental Hygene Agency, Aberdeen Proving Ground, Maryland 2 10 10
A gas-liquid chromatographic procedure (GLC) has been developed for the determlnatlon of hexamethylene dlisocyanate (HDI) in air. HDI is collected In an acidic absorbing solution where it is hydrolyzed to hexamethyienedlamine (HDA). HDA is extracted wlth toluene, derlvatlzed wlth heptafluorobutyrlc anhydride (HFBA), and subsequently analyzed by GLC using an electron capture detector. The method has a detectlon iimlt of 0.050 ng per 2-pL injection which corresponds to 0.53 ppb or 3.75 pg/m3 of HDI in a 40-L alr sample.
Diisocyanates are used to produce polyurethane adhesives, elastomers, rigid and flexible foams, and organic coatings. HDI based coatings have a unique combination of toughness, flexibility, solvent resistance, and light stability which has led to their widespread and continually increasing usage.
Personal exposure to isocyanates can cause irritation of the respiratory tract and may result in chronic impairment of pulmonary function. In 1978, NIOSH published criteria (1) for a recommended standard for six diisocyanates; the TWA limit recommended for HDI is 5 ppb or 35 pg/m3. Isocyanates react readily with compounds containing reactive hydrogens, e.g., acids, bases, water, etc.; this reactivity precludes collection of isocyanates from air without immediate derivatization. Various methods have been published for measuring diisocyanates in air. They all involve simultaneous collection and derivatization of diisocyanates followed by analysis using colorimetry, thin-layer chromatography (TLC), or high-performance liquid chromatography (HPLC). The colorimetric methods (2,3)rely on the formation of intensely colored diazo compounds derived from the reaction of aromatic amines (aromatic diisocyanate hydrolysis products) with a derivatization reagent. Since aliphatic amines do not respond to the diazotization reaction, this technique cannot be
Thls article not subject to U S . Copyright. Publlshed 1982 by the American Chemical Soclety
