Anal. Chem. 1982, 54, 117-123
low methamphetamine concentrations and before it at higher. If the ionic strength of solvent 2 is raised. by the addition of a salt such as sodium perchlorate the methamphetamine pealk becomes sharper and elutes always ahead1 of the MTQ peak.
(12) Gfeller, J. C.; Stockmeyer, M. J. Chromatogr. 1980, 798, 162. (13) Roth, W.; Beshke, K.; Jauch, R.; Zimmer, A,; Koss, F. W. J . Chromatogr. 1981, 222, 13. (14) Cantwell, F. F. Anal. Chem. 1978, 48, 1854. (15) Mohammed, ti. Y.; Cantwell, F. F. Anal. Chem. 1978, 50,491. (16) Ishli, D.; Hibi, K.; Asai, K.; Nagaya, M.; Mochizuki, K.; Mochida, Y. J. Chromatoor. 1978. 756. 173. (17) Baum, R. -6.; Saetre, R.. Cantwell, F. F. Anal. Chem. 1980, 52, 15. (16) Berry, D. J. J. Chromatogr. 1989, 42, 39. (19) Patel, D. M.; Visalli, A. J.; Zalipsky, J. J.; Reavy-Cantwell, N. H. I n Analytlcal Proflles of Drug Substances"; Florey, K., Ed.; Academlc Press: New York, 1975; Vol. 4. (20) Diem, K., Ed. "Documenta Geigy Scientific Tables", 6th ed.; Gelgy Pharmaceutlcals: Montreal, 1962; pp 553-555. (21) "Amberllte XAD-2", Technical Bulletin, Rohm and Haas Co.: Philadelphia, PA, 1972. (22) Christensen, J. M.; Holfort, S. J. Pharm. Pharrnacol. 1975, 25,538. (23) Boyd, G. E.; Adamson, A. W.; Meyers, L. S.,Jr. J. Am. Chem. Sac. 1947, 69,2836. (24) van Vliet, H. P. M., Bootsman, Th. C., Frei, R. W.; Brinkman, U. A. Th. J. Chromafogr. 1979, 785,483. (25) Snyder, L. I?.;Kirkland, J. J. "Introduction to Modern Liquid Chromatography", 2nd ed.; Wiley: New York, 1979; Chapter 5. (26) Ericsson, 0.; Danielsson, B. Drug Metab. Dlspos. 1977. 5. 497. (27) Ericsson, 0. Acta Pharm. Sueclca 1978, 75, 81. (28) Baker, J. K. J . Liq. Chromatogr. 1981, 4 , 271.
ACKNOWLEDGMENT Most of the drug arid metabolite sa:mples were kindly provided by Lester Chatten, Department of Pharmacy, University of Alberta. The authors thank the Chemistry Department Machine Shop for making the precolumn and the in-line filter and Lynne Fossey for performing preliminary experiments.
LITERATURE CITED (1) Kopjack, L.; Finkle, B. Si.; Lamoreaux, T. C.; Pierce, W. 0.; Urry, F. M. J . Anal. Toxlcol. 1979, 3 , 155. (2) Kuelpmann, W. R. J. Clln. Chem. Clin. Biochem. 1979, 77, 115. (3) Evenson, M. A.; Lensmeyer, G. L. Clin. Chem. (Wlnston-Salem, N . C.) 1974, 20, 249. (4) Cailleux, A.; Turcant, A,; Premel-Cabic, A,; Pdain, P. J. Chromatogr. Sci. 1981, 79, 163. (5) Gelbke, H. P.; Grell, T. IH.; Schmidt, G. Arch. Toxicol. 1978, 39, 21'1. (6) Gudzinowicz, El. J.; Gudzinowicz, M. J. "Analy!rls of Drugs and Metabo(7) (8) (9)
(IO) (11)
117
RECEIVEDfor review August 17, 1981. Accepted October 9, 1981. This work was supported by the Alberta Heritage Foundation for Medical Research, the Natural Sciences and Engineering Research Council of Canada, and the University of Alberta. Presented in part at 180th National Meeting of the American Chemical Society, Las Vegas, NV.
lites by Gas Chromatomgraphy-Mass Spectrometry"; Marcel Dekker: New York, 1977; Vol. 2, Chapter 1. Hodnett, C. N.; Eberhardt, R. D. J. Anal. Toxicol. 1979, 3 , 187. Eichelbaum, M.; Sonntag, B.; Von Unruh, G. Arch. Toxlcol. 1978, 4 , 187. Frei, R. W. Anal. Proc. 1980, 77, 519. Lankelma, J.; Poppe, HI. J. Chromatogr. 1978, 749, 587. DeJong, G. J. J . Chrocnatogr. 1980, 183, 203.
SeIect ive Detection of Amino PoIycyc Iic A romatic Compounds in Solvent Refined Cloal Douglas W. Later and Milton L. Lee* Department of Chemistry, Brigham Young Un,iversity, Provo, Utah 84602
Bary W. Wilson Pacific Northwest Laboratmy, Operated by Bzittelle Memorial Institute, Richland, Washington 99352
Quantitative derlvatiration of amlne-rlch Isolates of an SRC I1 heavy distillate coal liquid with trifluoroacetyl or pentaifluoropropyl anhydrlde enabled the selective detection and semlquantitatlon of fluoroamlde derlvatlvcss of the amlnes by caplllary column gas chlromatography In conjunctlon wlth an electron capture detector. Coupled gas chromatography/ mass spectrometry and both low- and high-resolution mass spectrometry were usedl in the identification of the derlvatired products and showed the presence of amino polycycllc aromatlc hydrocarbons having from two to six rings, some of which were highly alkylated. The presence of amino polycyclic aromatic nitrogen heterocycles (erg., aminoquinoline) which have not been prevlously reported in coal liquefactlon materlals was csnflrmed by hlgh-resolutlon mass spectrometry. The advantages oi formlng the fluoroamlde derlvatlves for both the gas chromatographic and miass spectral determlnation of amino polycycllc aromatic compounds In synthetic fuel materials are demonstrated.
Current U.S. policy which calls for the development of domestic energy resources has created a renewed emphasis on the production of liquid fuels from oil shale and coal. To reduce the environmental and occupational hazards associated 0003-2700/82/0354-0117$01.25/0
with the conversion and consumption of synthetic fuels, the development of methods for the identification and subsequent removal (1) of potentially genotoxic compounds in these materials is important. Amino polycyclic aromatic compounds, APAC, in synthetic fuels have recently become of increased concern because of the mutagenicity and carcinogenicity exhibited by this class of compounds. (In this paper, acronyms representing various classes of polycyclic aromatic compounds are used as outlined by Bartle et al. (2). PAC refers to the polycyclic aromatic compounds in general, including both hydrocarbons and heterocyclic compounds, while PAH refers only to the polycyclic aromatic hydrocarbons. PANH refers to the polycyclic aromatic nitrogen heterocycles, in which the nitrogen heteroatom is part of the ring structure. Therefore, 2O-PANH represents PANH in which the nitrogen heteroatom is part of a five-memberedring and has a hydrogen atom covalently attached (i.e., indole, carbazole), while 3 O PANH represents PANH in which the nitrogen heteroatom is part of a six-membered ring (Le., acridine). APAH refers to PAH which have an amino group attached to a carbon atom in the ring. N-PAC refers collectively to all PAC containing a nitrogen heteroatom.) The occurrence of APAH in coal-derived liquids and residues was reported as early as 1958 by Karr et al. (3). Other workers have implied or demonstrated the presence of APAH @ 1981 American Chemical Soclety
118
ANALYTICAL CHEMISTRY, VOL. 54, NO. 1, JANUARY 1982
having one or two aromatic rings in synfuel products by spectrophotometric analysis ( 4 , 5) and gas chromatography/mass spectrometry, GC/MS (6-8). The presence of APAH in mutagenically active coal liquid fractions has been demonstrated by use of amine-specific enzyme preparations for metabolic activation in modified Ames testing procedures (9). Wilson and Pelroy e t al. (10, 11) and Guerin et al. (12) have shown that fractions from synfuel materials containing large APAH show high levels of activity in several microbial mutagenicity assays. Pelroy and co-workers also reported that the biological activity of these same fractions was substantially reduced after treatment with nitrous acid which selectively destroys APAH, thus demonstrating a positive correlation between APAH content and mutagenicity (13). There are, however, a number of difficulties associated with the isolation and identification of APAH in complex mixtures. For example, it is difficult to obtain a pure APAH isolate using conventional adsorption and gel permeation column chromatography due to the coelution of APAH and other specific nitrogen-containing polycyclic aromatic compounds (N-PAC). Previously reported separation methods for the determination of APAH involve the use of Sephadex LH-20 column chromatography (14) as well as combinations of solvent extraction, acid-base partitioning, and thin-layer chromatography ( 5 , I I ) . Although these chromatographic procedures have been successfully used for the determination of a number of APAH in synfuel materials, there are several disadvantages associated with these methods. solvent extraction and partitioning methods are cumbersome and the formation of emulsions is common, leading to sample loss. In addition, a large number of fractions are often generated, and the separations obtained are usually inefficient, resulting in incomplete chemical class separation. This is important in light of the fact that direct mass spectral analysis gives virtually indistinguishable spectra for APAH and various methyl 3O-PANH. In addition, the elemental compositions of APAH are identical with those of the corresponding methyl 3O-PANH, and hence, the application of high-resolution mass spectrometry to the analysis of complex mixtures containing both types of compounds is of marginal benefit. A suitable derivatization technique such as fluoroacetylation which selectively alters only the APAH compounds solves many of the previously mentioned difficulties. In addition to tagging the amino compounds with an electron capturing tag for selective detection in capillary gas chromatography, an additional benefit is the change in elemental composition of the derivatized APAH relative to the PA", thus allowing direct analysis by probe inlet mass spectrometry. In this paper, the development of a rapid chemical class separation method and selective detection using fluorinated derivatives for the determination of APAH in coal-derived products is reported.
EXPERIMENTAL SECTION Sample Origin. A heavy distillate (HD)material (boiling point range 26Cb-450" C ) from the solvent refined coal (SRC IT) process was obtained from the Fort Lewis pilot plant operated by Pittsburgh & Midway Coal Mining Co. The SRC I1 HD was produced during the processing of West Virginia coal from the Pittsburgh seam. Since this SRC I1 HD was of pilot plant origin, it should not necessarily be considered as representative of coal liquid products which may eventually be produced on a commercial scale. Isolation of the APAH-Rich Fraction. Detaik of the column chromatoaauhic seuaration method used to isolate the APAH-rich fraction &v; been breviously described (15). A schematic diagram of the modified separation scheme used for this work is shown in Figure 1. Briefly, the nitrogen polycyclic aromatic compounds (N-PAC) were eluted with chloroform from neutral aluminum oxide. Next, the APAH were isolated from most of the other N-PAC by silicic acid adsorption chromatography. Several,
L1-l SAUPLE
* Neutral Alumina
Hexane
Beizene
Chlaroforn
I
A-1
A- 2
Figure 1. Chemical class separation scheme for synthetic fuel products. Key: polycyclic aromatic compounds (PAC), nitrogen polycyclic aromatic compounds (N-PAC), secondary nitrogen polycyclic aromatic heterocycles (2'-PANH), amino polycyclic aromatic hydrocarbons (APAH), and tertiary nitrogen polycyclic aromatic heterocycles (3'-
PA").
standard two-, three-, and four-ringAPAH were used to determine the elution parameters of the APAH fraction on silicic acid. Derivatization. The following APAH were purchased from Aldrich Chemical Co.: 1-aminonaphthalene, 2-aminobiphenyl, 4-aminobiphenyl, 2-aminofluorene, 1-aminoanthracene, 2aminoanthracene, 9-aminophenanthrene, 3-aminofluoranthene, 1-aminopyrene, and 6-aminochrysene. Approximately 50 pg of each aromatic amine was dissolved in 0.5 mL of benzene in a reaction vial, and 0.1 mL of 0.05 M trimethylamine (in benzene) was added. Next, 10 pL of either trifluoroacetic anhydride (MCB Manufacturing Chemists) or pentafluoropropionic anhydride (Regis Chemical Co.) was added to the reaction mixture; the vial was sealed and heated in a mineral oil bath at 50 "C for 15 min. The reaction mixture was then cooled for several minutes, 1.0 mL of 5% aqueous ammonia solution added to terminate the reaction, and the mixture shaken for 5 min. Finally, the organic and aqueous phases were allowed to separate and the benzene layer containing the derivatized APAH was recovered for subsequent analysis. This procedure was followed exactly for the derivatization of the APAH-rich fraction from the SRC I1 coal liquid heavy distillate. All organic solvents used were of pesticide grade, the water was deionized and doubly distilled, and the derivatizing reagents were used as purchased without additional purification. The stock ammonia reagent (30% NH,; Mallinkcrodt) used was extracted with equal portions of methylene chloride to remove any artifact organic compounds. GC and GC/MS. A Hewlett-Packard (HP) 5880 gas chromatograph equipped with a fused silica capillary column (20 m X 0.30 mm i.d.) coated with SE-52 (film thickness 0.25 pm) and both 63Nielectron capture detector (ECD) and flame ionization detector (FID) were used in this study. During chromatographic analysis, the oven was held at 50 "C for 2 min and then temperature programmed at 4 OC/min to a final temperature of 250 "C. The GC was equipped with a capillary injection system that was used in the vaporization splitless mode for sample introduction. Mass spectral identification of APAH-fluoroamidederivatives was accomplished by using coupled GC/MS. Gas chromatographic parameters were similar to those previously described. Low-resolution mass spectra were obtained on an HP 5982A quadrupole mass spectrometer operated in the electron impact
ANALYTICAL CHEMISTRY, VOL. 54, NO. 1, JANUARY 1982 mode at 70 eV electron energy. Spectra were acquired and processed with an H P 5934A data system. Semiquantitation of the APAH found in the SRC I1 HD was accomplished by spiking a portion of the original SRC I1 HD with 1-aminonaphthalene and comparing the resultant gas chromatographic-ECD peak are= with those of an unlspiked sample. Two determinations were averaged for the data listed in Table I. APAH present in lower concentrations than 15 pg/g were not reported. Probe Inlet Mass Spectral Analysis. Mass spectral analyses at both high-(HRMS)and low-resolution (LRIMS)were performed on a VG Micromass ZAB 1F double focusing mass spectrometer operated at BOO0 V accelerating potential. IIRMS spectra were scanned at a dynamic resolution in excess of 20000 at a rate of 30 s/mass decade. Data were acquired and stored on a PDPBA based VG 2035 data system. High boiling peIfluoroalkane (PFA) served as a mass calibratiion standard. For these analyses, the times of arrival of 46 "reference lock masses" from PFA between 100 and 550 amu were stored by the data system and used for the calibration of each HItMS scan. Prior t o the assignment of possible elemental composition by the data system, three or more spectra were averaged together to reduce the possible contribution of artifact mass peaks and to increase the measurement precision. The program which generated the possible elemental compositions was instructed to consider nitrogen, oxygen, sulfur, and fluorine as possible heteroatoms in the ions of the mass spectra. LRMS spectra were obtained at a resolutnon of 4000. A mass range of 200-600 m u was scanned to obtain nominal mass assignments for ions which were of insufficient abundance for detection and/or accurate mass assignment by HRMS.
RESULTS AND DISCUSSION S e p a r a t i o n and D e rivatization. Because the APAH[ occur at such low concentration levels in coal liquids, this class of compounds must be isolated prior to compound identification. The APAH elute in fraction S-2 using the two-step separation method outlined in Figure 1. However, as discussed by Later et al. (15), a few benzoquinolines, alkylbenzoquinolines, and naphthoquinolines coelute with the APAH in this fraction. This makes the assignment of exact compound structure by conventional methods difficult because many isomeric compounds having differeint molecular structures yield indistinguishable mass spectra. The derivatization of APAH t o either the corresponding trifluoroacetyl (TFA) or pentafluoropropyl (PFP) amides (eq 1)prior to GC and GC/N[S provides a solution to this problem.
TEMPERATURE
loci
Masuda and Hoffmann (16) used PFP derivatization to identify and quantify 1-and 8-aminonaphthalene in cigarette smoke condensate and reported yields excieeding 95% for the conversion of several standard APAH to IPFP-amide derivatives (17). Similar yields were observed iin the present work for the PFP-amides, however, somewhat lower conversion yields, 85-95%, were obtained for the AF'AKTFA derivatives. A recent paper by Tomkins and Ho (18) reported the use of trifluoroacetic anhydride in derivatize APAH in fossil fuel sources, followed by packed column gas chromatography with FID detection and GC/MS. Treatment of 3'-PANH standards (e.g., acridine) by this derivatization method produced no detectable PFP- or TFA-amide derivatives. However, some 2O-PANH,specifically carbazole, reacted t o give approximately 20% conversion to the corresponding fluoroamide derivative when subjected to
mo 10
0
250
200
150
20
40
30
50
60
Figure 2. Capillary column, FID, gas chromatograms of (A) underivatized and (6)PFP-derivatized APAH standard compounds. Conditions: 20 m X 0.30 mm i.d. fused silica capillary column coated with SE-52, temperature programmed from 40 to 250 O C at 4 'C/min. Key: (1) I-aminonaphthalene, (2)2-aminobiphenyl, (3) 4-aminobiphenyl, (4)
2-amlnufluorene, (5) 1-aminoanthracene and 9-aminophenanthrene, (6) 2-aminoanthracene, (7)3-aminofluoranthene,(8) 1-aminopyrene, and (9) 6-aminochrysene. 3
i
+-
T E M P E R A T U R E l°Cll TlME lrnl",'
n
,
5a TIME lminlc-
110
1
;
A
si,
100 10
h
150
*o
30
250
200 40
0
Flgure 3. ECD capillary gas chromatogram of several (A) PFPderivatized and (6)underivatized APAH standard compounds. Conditions: 30 m X 0.31 mm i.d. fused silica capillary column coated with SE-52, temperature programmed from 40 to 250 O C at 4 OC/min. Peak numbers and compounds are listed in Flgure 2.
TFA or PFP anhydride. The fact that some ZO-PANH can be partially derivatized reemphasizes the importance of separating the 2O-PANH from the APAH by silica adsorption chromatography prior t o derivatization and subsequent identification of the fluoroamide compounds. GC and GC/MS. The gas chromatographic retention times of an APAH and its corresponding fluoroamide derivative are significantly different. In Figure 2, retention time shifts and variations in chromatographic profiles are observed for a number of standard APAH as compared to their PFP derivatives. Comparison of FID chromatographic profiles and retention time shifts of underivatized and derivatized APAH-rich fractions of synthetic fuel products were used for preliminary screening for the occurrence of APAH in these matrices. However, selective detection of the TFA- and PFP-amide derivatives of APAH by ECD gas chromatography or GC/MS takes full advantage of the properties conferred by the derivatization with regard to identification of individual components.
120
ANALYTICAL CHEMISTRY, VOL. 54, NO. 1, JANUARY 1982
Table I. Compounds Identified in the APAH-Rich Fraction of an SRC I1 Heavy Distillate Coal Liquid
compound amino indan C,-aminoindan aminonaphthalene C,-aminonaphthalene C2-aminonaphthalene C,-aminonaphthalene aminoquinoline C,-aminoquinoline C,-aminoquinoline C,-aminoquinoline C,-aminoquinoline aminoacenaphthylene/aminobiphenyl
C,-aminoacenaphthylene/ aminobiphenyl C,-aminoacenaphthylene/ aminobiphenyl C,-aminoacenaphthylene/ aminobiphenyl C,-aminoacenaphthylene/ aminobipheny 1 aminofluorene C,-aminofluorene C2-aminofluorene C,-aminofluorene C,-aminofluorene aminocarbazole C,-aminocarbazole C,-aminocarbazole C,-aminocarbazole aminoanthracene/aminophenanthrene
C,-aminoanthracene/ aminophenanthrene C,-aminoanthracene/ aminophenanthrene C,-aminoanthracene/ aminophenanthrene C,-aminoanthracene/ aminophenanthrene C,-aminoanthracene/ aminophenanthrene aminophenanthridine/aminoacridine C ,-aminophenanthridine/ am inoacrid ine C,-aminophenanthridine/ aminoacridine C,-aminophenanthridine/ am inoacrid ine aminophenylnaphthalene C,-aminophenylnaphthalene C,-aminophenylnaphthalene C,-aminophenylnaphthalene C,-aminophenylnaphthalene aminofluoranthene/aminopyrene C,-aminofluoranthene/aminopyrene C,-aminofluoranthene/aminopyrene C,-aminofluoranthene/aminopyrene C,-aminofluoranthene/aminopyrene aminochrysene/aminobenzanthracene
C,-aminochrysene/ aminobenzanthracene C,-aminochrysene/ aminobenzanthracene C,-aminochrysene/ amino benzanthracene C,-aminochrysene/ amino benzanthracene aminobenzo [ghilfluoranthenel aminocyclopentapyrene C, -aminobenzo[ghi]fluoranthene/ aminocyclopentapyrene C,-aminobenzo [ghi]fluoranthene/ aminocyclopentapyrene C,-aminobenzo [ghi]fluoranthene/ aminocyclopentapyrene
mol wt PFP parent derivative
concn,b method of identificationa
IZgk
131 14 5 143 157 171 185 144 158 172 186 200 169 183
277 291 289 303 317 331 290 304 318 332 346 315 329
GC/MS, LRMS LRMS GC/ECD, GC/MS, LRMS GC/ECD, GC/MS, LRMS GC/ECD, GC/MS, LRMS LRMS LRMS, HRMS LRMS, HRMS LRMS, HRMS HRMS HRMS GC/ECD, GC/MS, LRMS GC/ECD, GC/MS, LRMS
237.3d 155.8
197
343
GC/ECD, GC/MS, LRMS, HRMS
102.7
211
357
LRMS
225
371
LRMS
181 195 209 223 237 182 196 210 224 193 207
3 27 341 355 369 383 328 342 3 56 370 339 353
GC/ECD, GC/MS, LRMS, HRMS GC/MS, LRMS, HRMS GC/MS, LRMS, HRMS LRMS LRMS LRMS, HRMS LRMS, HRMS LRMS
221
367
GC/MS, LRMS, HRMS
235
381
LRMS, HRMS
249
395
LRMS, HRMS
263
409
LRMS, HRMS
194 210
340 3 54
LRMS LRMS, HRMS
2 24
368
LRMS, HRMS
238
382
LRMS, HRMS
219 233 247 261 275 217 231 24 5 259 273 243 257
365 379 393 407 421 363 377 391 405 419 389 403
GC/MS, LRMS GC/MS, LRMS GC/MS, LRMS GC/MS, LRMS LRMS GC/ECD, GC/MS, LRMS GC/MS, LRMS, HRMS GC/MS, LRMS, HRMS LRMS, HRMS LRMS GC/ECD, GC/MS, LRMS LRMS, HRMS
271
417
LRMS, HRMS
285
431
LRMS
299
445
LRMS
241
387
LRMS
255
401
LRMS
269
415
LRMS
283
429
LRMS
204.3c 100.6 95.2
121.2
153.2=
49.0f
18.7
ANALYTICAL CHEMISTRY, VOL. 54, NO. 1, JANUARY 1982
121
Table I (Continued) mol wt PFP parent derivative 297 443
cornpound C,-aminobenzo [ghi]fluoranthene/ aminocyclogentapyrene amino benzopyrene/aminoperylene/ aminobenzofluoranthene C,-aminobenzopyrene/ aminoperylene/ amino benzofluoranthene C -amino be nzop yrene/ amino perylene/ amino benzofluoranthene C,-amino benzopyrene/ aminoperylene/ amino benzofluoranthene C,-aminobenzopyrene/ aminoperylene/ amino benzofluoranthene aminodibenzopyriznel
method of identificationa LRMS
267
413
LRMS, HRMS
281
427
LRMS, HRMS
295
44 1
LRMS
309
455
LRMS
323
469
LRMS
317
463
LRMS
331
477
LRMS
concn,b pg/g
aminodibenzofluoranthene
C,-aminodibenzopyrene/ aminodibenzofluoranthene
a GC/ECD = capillary gas chromatography/electron capture detector (retention data), GC/MS = capillary gas chromatogConraphy/mass spectrometry, LRMS = low-resolution mass spectrometry, HRMS = high-resolution mass spectrometry. centration in pg/g of APAH in crude SRC! I1 heavy distillate. Average value of two determinations using an internal standard of 1-aminonaphthdene. APAH for which quantitative data are not presented are lower in concentration than 1 5 pg/g. Two isomers of aminonaphthalene were identified by retention data: (1)1-aminonaphthalene, 42.9 pg/g; (2) 2-aminonaphthalene, 161.4 pg/g. d Two isomers of aminobiphenyl were identified by retention data: (1)3-aminobiphenyl, 141.5 pg/g; (2) 4-aminobiphenyl, 95.8 pg/g. e Three different isomers detected (see Figure 4): (1)48.0 pg/g, (2) 58.0 pg/g, ( 3 ) 47.2 pg/g. f Two different isomers detected (see Figure 4): (1)31.0 pg/g, (2) 18.0 pglg.
A
I1
l4 I
LL--2L-L
I
!
~
TEUPERATURE
,,ME
c m n,
150
100
0 1
0
20
30
250
200 40
50
Figure 4. ECD capillary gas chromatogram of PFP derivatized APAH (fraction S-2) in SRC I1 HD. Conditions as in Figure 3. Key: (1) aminonaphthalene,(2) 2-aminonaphthalene, (3)Cl-aminonaphthalenes, (4) C,-aminonaphthalenes, I@) 3-aminoblphenyl,(6) 4-aminobiphenyl, (7) C,-amInoblphenyl, (8) C2-aminobiphenyl,(9)aminofluorene, (10-12) aminoanthracenes/aminophenanthrenes,(13)arnlnofluoranthene,and (14) aminopyrene.
A GC-ECD trace of several PFP dlerivatized APAH[ standard compounds is ~ h o w nin Figure 3A. The underivatized standards, Figure 315, gave minimal ECD responses. The selectivity of the ECD for the derivatized amines over the underivatized amines was found to be greater than 1OoO:l for a number of compounds tested. Furthermore, comparison of peak area data indicate tlhat the ECD response factor is nearly an order of magnitude greater for the PFP derivative as compared with the TFA derivative for a given APAH. Since the APAH comprise approximately 15% by weight of the 5-2 (amine-rich) fraction, the selectivity of the ECD for the derivatized APAH over the other nitrogen heterocyclic compounds which are found in this fraction is an important factor. I t was found that the scalectivity of the I X D for the PFPderivatized 9-aminophenanthrene over benzo[flquinoline wa~, 50000:1, which is of sufficient magnitude to rule out any
interference from underivatized 3O-PANH. Figure 4A is an ECD capillary gas chromatogram of the APAH-rich fraction of the SRC I1 HD that was derivatized with PFP anhydride. The underivatized APAH isolate produced no significant ECD response when chromatographed a t the same concentration under identical GC conditions (see Figure 4B). The fact that the 3O-PANH, some of which are present in this fraction, fail to react with the TFA and PFP anhydride and are not ECD sensitive, confirms the usefulness of this technique. The separation of complex mixtures into discrete components by capillary column gas chromatography and the subsequent identification of these components by mass spectrometry is a valuable analytical technique. The mass spectral determination of PFP- and TFA-derivatized APAH is particularly straightforward and is especially useful for APAH that occur in crude isolates with 3O-PANH. For example, the methylbenzoquiinolines and aminophenanthrene have the same molecular weight (193 amu) and it is difficult to distinguish these species by their mass spectra alone. GC retention data can assist in distinguishing these two types of compounds, but when several isomers of each of these classes occur together in a complex mixture, structural assignment by GC retention becomes difficult and oftentimes impossible. However, when aminophenanthrene is derivatized with TFA or PFP anhydride, the molecular weight is increased by 96 or 146 mass units, making differentiation between the two species of compounds by mass spectral data straightforward. Since the acetylation reactions are selective, only the APAH are converted to higher molecular weight compounds. Derivatized APAH have characteristic fragmentation patterns that provide supplemental information for identification. Figure 5 shows the fragmentation of the TFA derivative of aminopyrene and is typical for APAH-TFA compounds. The parent ion at m / e 313 gives the molecular weight of the derivatized compound. Two other major ions are present: (1) the (M - 97)+ ion corresponds to the loss of the TFA group
ANALYTICAL CHEMISTRY, VOL. 54, NO. 1, JANUARY 1982
122
An enriched APAH fraction of the SRC I1 HD was derivatized with TFA anhydride and the sample analyzed by capillary GC/MS. Figure 6 shows a composite of several selected ion plots of APAH-TFA compounds identified in this coal liquid. In addition to these compounds, many additional compounds including alkyl APAH have been identified in the SRC I1 HD by capillary GC/MS and are presented in Table I. Probe Inlet Mass Spectrometry. Both the derivatized and nonderivatized APAH fractions were analyzed by probe inlet HRMS. The derivatized SRC I1 HD samples appeared to evaporate evenly into the MS ion source and left no visible residue on the glass sample holder. Residue remained on the glass sample holder, however, after analysis of the nonderivatized material. Inspection of the elemental composition assignments for the HRMS spectra of the derivatized fraction showed the presence of compounds having the derivatized primary amino group. Since no structural information other than ion elemental composition is available from the HRMS data, tentative structural assignments presented in Table I were made by assuming the presence of the amino analogues for PAC ring systems known to be present in coal liquid materials. Assignments of structures having up to four aromatic rings were also based on GC retention times and spectra from GC/MS analysis. For compounds larger than four rings, or for those not detected by GC/MS, no attempt was made to distinguish among ring systems of equally probable isomeric form. Of particular interest is the presence of amino polycyclic aromatic nitrogen heterocycles (APANH) such as aminoquinolines in this heavy distillate (see Table I). This is the first reported detection of these compounds in coal liquids. APANH are currently being subjected to Ames assay to determine if they are mutagenically active. The aminocarbazoles are of particular interest due to their structural similarity to recently reported comutagens (19,ZO). The enhanced sensitivity of LRMS relative to HRMS was useful in identifying higher molecular weight APAH having more than four rings, which were present in extremely low concentrations. LRMS was applied mainly to the PFP-derivatized materials since the large molecular weight increase of 146 amu resulting from the derivatization helped to distinguish APAH from PANH. A representative LRMS scan from the derivatized APAH-rich isolate of the HD is shown in Figure 7. Two distinguishable envelopes are present, the higher masses represent the parent ions and the lower envelope represents the corresponding (M - 147)' and underivatized 3O-PANH ions. No ions above m / e 250 were observed when the underivatized fraction was analyzed under identical LRMS conditions. APAH having as many as six rings were detected by this method. Alkyl homologues from C1to C4 were also observed for most of the parent ring structures.
100.
80.
AMINOPYRENE -TFAA
60.
40.
I
20,
0 1W
I
60
I
20
I
0 180
200
240
220
260
300
280
320
Figure 5. Mass spectrum of 1-aminopyrene TFA derivative.
1 ,
AMINOPYRENE AMINOFLUORANTHENE
AMINOPHENANTHRENE
il?
AMINOFLUORENE
AMINOBIPHENY 1
AMINONAPHTHALENE
2
9
10
II
12
I3
14
15
16
17
I8
19
2
21
22
23
24
25
26
21
Figure 6. Reconstructed selected ion mass spectral plots of TFAderivatized APAH in the SRC I1 HD sample. and gives the molecular weight of the underivatized aromatic amine less one mass unit (the proton lost during derivatization), (2) the other prominent ion in the mass spectrum results from the loss of HCN (27 mass units) from the (M - 97)' fragment. Similar fragmentation patterns are observed with APAH-PFP derivatives with the major fragment ion corresponding to the loss of the PFP group, (M - 147)'.
100-
218
327
341
365367
1
381
3791
A
200
300
400
500
rn/B
Figure 7. Direct inlet probe LRMS of PFP-APAH fraction of the SRC I1 HD. The spectrum is from a single scan obtained at a nominal probe temperature of 260 O C .
Anal. Chem. 1982, 5 4 , 123-125
ACKNOWLEDGMENT The authors thank Keith Knauss of Hewlett-Packard, Avondale Division, and Cherylyn Willey of Pacific Northwest Laboratory for their technical assistance.
LITERATURE CITED (1) Wilson, B. W.; Peterson, M. R.; Pelroy, R. A.; Cresto, J. T. Fuel1981, 60, 289-294. (2) Bartle, K. D.; Lee, M. L.: Wise, S. A. Chem SOC. Rev. 1981, 35, 113-158. (3) Karr, C.; Chang, T, L. J . Insf. Fuel1958, 31, 522-527. (4) Brown, D.; Earnshaw, 0.G.; McDonald, F. FI.; Jensen, H. G. Anal. Chem. 1970, 42, 146-151. (5) Ho, C.-h.; Clark, B. R.; Guerin, M. R.; Ma, C. Y.; Rao, T. K. Prepr. Pop.-Am. Chem. Soo., Div. FuelChem. 1979, 2 4 , 281-291. (6) Paudler, W. W.; Chaplin, M. Fuel 1979, 58, 775. (7) White, C. M.; Schweighardt, F. K.; Shultz, J. L. Fuel Process. Techno/. 1978, 1 , 209-215. (8) Schiller, J. E. Anal. Chcrrn, 1977, 49, 2292-2294. (9) Pelroy, R. A,; Gandolfi, 14. Mutat. Res. 1980, 72, 329-334. (IO) Wilson, B. W.; Pelroy, R. A. I n "Proceedings of the 25th Annual Conference on Mass Spectrometry and Allied Topics"; Seattle, WA, June! 1979, pp 23-24.
123
(11) Wilson, B. W., Pelroy, R. A.; Cresto, J. T. Mutat. Res. 1980, 79, 193-202. (12) Guerin, M. R.; Ho, C.-h.; Rao, T. K.; Clark, B. R.; Epler, J. L. Envlron. Res. 1980, 2 3 , 42-53. (13) Pelroy, R. A.; Stewart, D. L. Mufat. Res., in press. (14) Toste, A. P.; Pelroy, R. A.; Sklarew, D. S.In "Proceedings of the 20th Hanford Life Sciences Symposium"; Richland, WA, Oct 1981. (15) Later. D. W.: Lee. M. L.: Bartle. K. D.: Kona. R. C.: Vassllaros. D. L. Anal. Chern'. 1981, 53,' 1612-1620. (16) Masuda, Y.; Hoffrnann, D. Anal. Chern. 1969, 4 1 , 650-652. (17) Masuda, Y.; Hoffrnann, D. J . Chrornatogr. Sci. 1969, 7 , 695-697. (18) Tomklns, B. A.; Ho, C.-h. Anal. Chem. 1982, 5 4 , 91-96. (19) Nagao, M. T., et al. Proc. Jpn. Acad. 1977, 5 3 , 95-98. (20) Nagao, M. T., et al. Proc. Jpn. Acad., Ser. B 1977, 5 3 , 34-37.
~.
1
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RECEIVED for review June 10, 1981. Accepted October 15, 1981. This work was supported by the Department of Energy, Contract No. V-l384843AV, with Pacific Northwest Laboratory, and the Department of Energy, Division of Biomedical and Environmental Research, Contract No. DE-AC0279EV101237, with Brigham Young University.
Evaluation of the Solubility Product of Nickel Complexes by the Competitive Effect of Ethylenediaminetetraacetic Acid Daniel Rosales and Jos6 M. Cano-Pa&* Department of Analytical Chemistty, Faculty
of Chemistty, The
University, Sevilla-4, Spain
A simple procedure for the evaluation of the solubility product of slightly soluble complexes is reported. Pertinent experimental data are obtained by weighing the liisoluble complexes before and after treatmlent with the appropriate EDTA and buffer solutions. The mcbthod requfres careful control of pH1 but no conductometrlc or colorimetric rneasurements are needed. The applicatioin to several comlplexes of nickel is also reported and the results are compared wlth literature data.
We report in this paper a simple procedure for the determination of the solubility product of insoluble complexes, and it is applied to several complexes of nickel with thiosemicarbazones, dimethylglyoxime, and 8-hydroxyquinoleine. This method is based in the competition between EDTA and the corresponding ligand for the nickel ions, in a basic medium. It is only necessary to weigh the insoluble complex before and after treatment with the EDTA solution and carefully measure the p H of the resulting solution.
Several procedures for the evaluation of solubility products of some complexes of nickel and other metal ions have been devised. The solubility product of nickel- dimethylglyoxime at 25 "C was measured by Christopherson stnd Sandell (1)and by Babko and Mikhel'son (2) by determining the solubility of the nickel complex in acidic solutions; however, the decrease of acidity seemed to increase the time required to attain solubility equilibrium, and measurement of the solubility products in saturated solution with the ligand is not practical since the concentration of nickel ions is reduced to about mol/L. Wenger et al. (3) measured the solubility product of nickel nioxime a t 25 O C by determining the pH at which the complex just begins to precipitate from an acidic solution. It was found that the value obtained depends upon the rate of addition of the sodium hydroxide and the color one takes for the end point. Banks and Barnum (4) devised a procedure in which nickel chloride and uic-dioxime were simply mixed in the stoichiometric amounts a t the desired temperature and shaken for 2 h and then the p H was measured. They proposed an equation for the solubility product and found a value of 2.19 X a t 25 O C for the nickel-dimethylglyoxime complex.
Synthesis and Study of Nickel-Thiosemicarbazones Complexes. To 250 mL of an aqueous solution of nickel nitrate containing 10-50 mg of nickel(II), in ammonia buffer medium (pH 9-11), a solution of thiosemicarbazone in ethanol (0.249%) was slowly added with constant stirring, until a small excess was present. The precipitate was collected in a no. 4 porosity sintered-glass crucible, washed with an ethanol-water mixture, and dried at 70-100 "C to constant weight. Nickel complexes of furfural thiosemicarbazone, thiophen-2-aldehyde thiosemicarbazone, and furfural 4-phenyl-3-thiosemicarbazonehave been isolated. Elemental analysis confirms the quality of the complexes obtained. The composition of these complexes corresponds to a formula NiL2, HL being the neutral ligand. Infrared spectra were recorded by using KBr disks on a Beckman Acculab-2 spectrometer. Hydrogen-1NMR spectra were obtained at 60 MHz on a Perkin-Elmer R-12B instrument, in Me2SO-d6solutions. Magnetic susceptibilities were measured by the Gouy method, Complexes are diamagnetics. The spectral data as well as magnetic susceptibilities suggest that the nickel complexes posses a square planar arrangement. Synthesis of Nickel-Dimethylglyoxime and -8-Hydroxyquinoleine Complexes. Ordinary procedures for precipitation of both complexes were used (5). Determination of Solubility Products. To weighed amounts of the slightly soluble complexes in 100-mLvolumetric flasks,were
EXPERIMENTAL SECTION
0003-2700/82/0354-0123$01.25/00 1981 American Chemical Society
