Triple-Quadrupole Mass Spectrometry Studies of Nitroaromatic Emissions from Different Diesel Engines Thomas R. Henderson,* James D. Sun, Robert E. Royer, Charles R. Clark, and Albert P. Lit
Lovelace Inhalation Toxicology Research Institute, Albuquerque, New Mexico 87 185 1. Michael Harvey and Donald H. Hunt
Department of Chemistry, University of Virginia, Charlottesvills, Virginia 2290 1 John E. Fulford, Annette M. Lovette, and Wllllam R. Davldson
Sciex, Inc., Toronto, Canada
rn Triple-quadrupole mass spectrometry (MS/MS) has been used to compare nitroaromatic emissions from two different types of diesel engines, a direct-injection, single-cylinder engine and an indirect-injection V-8 engine. The low level of nitropyrenes/nitrofluoranthenes in exhaust extracts may be due in part to the low pyrene content of the reference fuel used. Addition of pyrene to reference fuel resulted in increased pyrene in exhaust extracts, but only minor differences in mutagenicity. Only about 1/1000 of the total mutagenicity from complete reaction with NOz appeared to have occurred during diesel exhaust and soot collection on filters. Fractionation with MezSO was found to be useful in separating aliphatic hydrocarbons from mutagenic activities and in concentrating nitroaromatic compounds for MS/MS analysis. Concentration of certain nitroaromatic compounds was necessary for isobutane chemical ionization MS/MS, while atmospheric pressure MS/MS appeared capable of detecting nitroaromatic compounds even in unfractionated extracts. MS/MS comparisons of concentrated samples of differing mutagenicities showed the main differences were increased ion intensities of dinitro compounds in more mutagenic samples. It is concluded that the polynitro compounds may be of more significance than mononitro compounds in the mutagenic activities that have been found associated with diesel soot.
Introduction Use of diesel engines in light-duty vehicles has been increasing because of increased fuel efficiency, the ability of diesel engines to utilize a wide range of fuels, and the lower taxation on diesel fuels in certain countries. The presence of direct-acting mutagens in diesel exhaust emissions (1-4) has generated concern over potential health effects that may occur from increased diesel emissions. Correlations between the presence of nitro polycyclic aromatic hydrocarbons (nitro-PAHs) in environmental extracts and mutagenic activity have been observed (5-8). New analytical approaches are needed to identify the mutagenic activities in exhaust extracts and measure the 'Present address: Environmental Health Laboratory, Monsanto Co., St. Louis, MO 63166 00 13-936X/83/09 17-0443$01.50/0
effects of different diesel engine designs and fuel formulations. Schuetzle et al. (9) have used triple-quadrupole mass spectrometry (MS/MS), high-resolution MS, and HPLC to compare exhaust extracts from three different makes of light-duty diesel vehicles. The differences in exhaust mutagenicity were quantitatively linked to the differences in mononitropyrene concentrations in each exhaust extract. However, only 10-20% of the exhaust mutagenicity was relatable to the mononitropyrenes. The exhaust sample studied in detail was from a malfunctioning prototype Nissan engine (10) and thus did not represent emissions from a production line engine. Clark et al. (11)have shown that exhaust mutagenicity varied 2-4-fold when one engine type was operated on fuels of differing aromaticity. Other engines of differing designs showed less than a 2-fold variation in mutagenicity when operated on the same range of fuels. Fuel variations as well as engine design may affect exhaust mutagenicity, but new methods are needed to elucidate the nature of these differences. Comparison of diesel soot extracts by MS/MS may be a useful initial approach to evaluate the relationships between mutagenicity of diesel exhaust and nitro-PAHs. MS/MS spectra showed that nitro-PAHs of similar molecular weights were present in soot extracts and fuel PAHs treated with NO2,suggesting a contribution of unburned fuel to exhaust mutagenicity (7). In the studies reported here, MS/MS analyses were used to compare diesel soot extracts and chemical fractions from two different types of diesel engines. Determination of the type of nitro-PAHs present in soot extracts enables selection of nitro-PAH compounds for synthesis as standards and for more quantitative estimates of the contribution of individual nitro compounds to mutagenicities present in exhaust.
Methods
A standard no. 2 diesel reference fuel was utilized in the experiments reported here. The PAH composition of this fuel has been reported previously (7). The one-cylinder diesel was a Swan engine (Jintang Diesel Engine works, The Peoples Republic of China) and the eight-cylinder
@ 1983 American Chemlcal Society
Environ. Sci. Technol., Vol. 17, No. 8, 1983
443
Table I. Samples Utilized for MS/MS Analysis
sample
TA 9 8 direct Mutagenicity, revertants/Mg
I
435
Ia Ib I1
1086 702 9.7
IIa
57.4
IIb
16.7
IIC I11
E10'
I-
0 4:
a
+
2a W
I 171
214
1,000-
2 I-
t
t 6Y
B
A Fuel Nitro-PAHs 0 Swan Diesel 0 Oldsmobile Diesel
-
I-
z
z
0
0
i I
l o 3-
0
105
L
OO 1o;bo
1;o
1bo
2;o 2Ao MASS ( M E )
2b0
2;o
260
Flgure 2. Mutagenicity (A) and MS/MS comparisons of the nitro-PAHs (B) of diesel fuel and engine exhaust extract fractions: (A)sample I; (U) sample IIa; (0)sampie I I I a . Mutagenicity was determined by using Salmoella Qqhimurlumstrain TA98. Nitro-PAHs were determined by Finnigan (M-17) MS/MS analysis.
I
5 1
0.01
011
,.bo
PERCENT PYRENE ADDED T O FUEL ( w l v )
Flgure 3. Effects of adding pyrene to diesel fuel on single-cylinder diesel exhaust extracts: MS/MS results. Pyrene was added to reference diesel fuel in the indicated grams/100 mL (w/v). The exhaust extracts were fractionated with Me,SO and analyzed by GC/MS for PAHs. The unfractionated extracts were analyzed by API/MS/MS for 46-) and dinitropyrene ( m l z 292467. nitropyrenes ( m l r 247-
-
446
Environ. Sci. Technol., Vol. 17, No. 8, 1983
+
0.01
0.1
10
PERCENT PYRENE ADDED TO FUEL (w/v)
Figure 5. Effects of adding pyrene to diesel fuel: mutagenicity. The conditions were as in Figure 3. The unfractionated extracts were assayed with Salmonella strains TA98 and TA100. The extracts were also reacted with excess NO, to determine the mutagenic activity after all PAHs had reacted.
API/MS/MS were in the linear response range of the instrument and to quantitate nitropyrene concentrations. These results are shown in Figure 4. The response to standard nitropyrene additions was linear. The detection limit of the instrument for nitropyrenes was in the picogram range. The calculated nitropyrene concentration was 432 ppm or
