Anal. Chem. 1984, 56,781-786
between the various component species.
COMPUTATIONS All computations were accomplished with a 48K Apple 11+ microcomputer. Information concerning the algorithms is available from E.R.M. Registry No. H2S04,7664-93-9.
781
Knorr, F. J.; Futreii, J. H. Anal. Chem. 1979, 57, 1236. Roscoe, Bradley A.; Hopke, Philip K. Anal. Chim. Acta 1981, 732, 89. Irish, D. E.; Chen, H. J . Phys. Chem. 1970, 74,3796. Ikawa, S.; Kimura, M. Bull. Chem. SOC.Jpn. 1976, 4 9 , 2051. Kreevoy, M. M.; Mead, C. A. Discuss. Faraday SOC. 1985, 3 9 , 166. Librovich, N. B.; Mairov, V. D. Izv. Akad. Nauk SSSR, Ser. Khim. 1977, 684; (Engl. Trans/.) 1977, 621. (10) Zarakhani, N. G.; Markin, V. S.;Zaikov, G. E. Zh. Fiz. Khim. 1979, 53,2294; (Engl. Trans/.) 1979, 53, 1306. (11) Chen, H.; Irish, D. E. J. Phys. Chem. 1971, 75,2672. (4) (5) (6) (7) (8) (9)
LITERATURE CITED (1) Maiinowski. Edmund R.; Howery, Darryl G. “Factor Analysis in Chemistry”; Wiley: New York, 1980. (2) Cox, Robin A.; Haldna, Uio L.; Idler, K. Loraiee; Yates, Keith Can. J . Chem. 1981, 5 9 , 2591-2598. (3) Mailnowskl. Edmund R. Anal. Chim. Acta 1982, 734, 129-137.
RECEIVED for review November 2, 1983. Accepted January 16, 1984. Presented in part a t the 17th Middle Atlantic Regional Meeting, Pocono Hershey Resort, White Haven, PA, on April 7, 1983.
Isolation of Mononitrated Polycyclic Aromatic Hydrocarbons in Particulate Matter by Liquid Chromatography and Determination by Gas Chromatography with the Thermal Energy Analyzer Bruce A. Tomkin$,* Roswitha S. Brazell, Mary E. Roth,’ and Vanessa H. Ostrum2 Analytical Chemistry Division, Oak Ridge National Laboratory, P.O. Box X,Oak Ridge, Tennessee 37831
Nkrated polycyclic aromatic hydrocarbons (NPAH), which are extracted ultrasonically from particulate matter, are fractionated conveniently wlth a semipreparatlve scale hlgh-pressure liquid chromatographic system. The NPAH present In the enriched Isolate are determlned by use of a gas chromatograph equlpped wlth a thermal energy analyzer (TEA). Turnaround time Is 8 h per sample. The HPLC separatlon permlts selectlvlty for NPAH by excluding other nitro compounds. The TEA exhibits a llnear response over 3 or 4 orders of magnkude (detection limk Is 0.3 ng of NPAH at S / N 2) whlle discrlmlnatlng agalnst hundred-fold or greater excesses of nonnltrated species. Recoveries of lndlvldual NPAH vary slgnlflcantly and depend upon the sample matrix, test compound, and spike concentratlon.
-
Nitrated polycyclic aromatic hydrocarbons (NPAH), a class of potent direct-acting mutagens (1-3), are produced in trace concentrations from combustion processes (4) or by the reaction of particulate polycyclic aromatic hydrocarbons (PAH) with smog or NOz (1). Because these nitrated species are so biologically important, precise and facile analytical methods which can determine their concentrations accurately a t the sub-part-per-million level are needed. NPAH are normally extracted from particulate matter (urban dust, air particulates, diesel soot, or stack ash) by using the conventional but time-consuming Soxhlet procedure. Fractionation and enrichment have been achieved withsemipreparative scale high-pressure liquid chromatographic (HPLC) columns packed with silica (5-8). These columns, however, are very sensitive to slight changes in the water content of the eluent and typically do not produce true “clean” ‘Department of Chemistry, Kenyon College, Gambier, OH 43022. Department of Chemistry, University of Tennessee, Knoxville, TN 37916. 0003-2700/84/0356-0781$01.50/0
fractions, Ramdahl et al. (9) reported many oxygenated species in urban air particulate isolates prepared by using such a column. Certain deficiencies in the isolation procedure may be tolerated if the final determination is achieved with a detector which exhibits high selectivity and reasonable to excellent sensitivity. A variety of gas chromatographic, liquid chromatographic, and mass spectrometric detectors have been applied to this problem (10-19). Most of these suffer from one or more of the following disadvantages: (a) insufficient selectivity (sample would require much more extensive cleanup), (b) insufficient sensitivity, or (c) excessive cost for routine use. In our method for determining NPAH, samples are extracted rapidly but efficiently by ultrasonic extraction procedures (20). Fractionation and enrichment are accomplished with a semipreparative scale aminosilane column which is less sensitive to water than a silica column but which also does not produce a completely interference-free fraction. Final detection is achieved with the gas chromatographic thermal energy analyzer (TEA). This detector has good sensitivity for NPAH compounds (21) and has exhibited excellent selectivity for nitrated aromatic compounds present in a difficult matrix, biological sludges (22). Recovery corrections are performed with either radioactively labeled nitroaromatic tracers or nonradioactive nitroaromatic species. The method is readily applied to particulate samples of interest.
EXPERIMENTAL SECTION Solvents and Chemicals. The solvents used in this work were “Distilled in Glass” grade (residue-free),purchased from Burdick & Jackson Laboratory (Muskegon, MI), and used as received. Most of the standard NPAH described were purchased from Pfaltz and Bauer, Inc. (Stamford, CT), the Aldrich Chemical Co. (Milwaukee, WI), or Foxboro/Analabs (North Haven, CT). Small quantities of 2-nitrobiphenyland 4-nitrobiphenylwere furnished by Curt White, Pittsburgh Energy Technology Center (Pittsburgh, PA). Authentic 1-methyl-9-nitroanthracene, 1-methyl-10-nitroanthracene, and 9-methyl-10-nitroanthracene were supplied by 0 1984 American Chemical Soclety
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ANALYTICAL CHEMISTRY, VOL. 56, NO. 4, APRIL 1984
P. Ruehle, Midwest Research Institute (Kansas City, MO). All solids were used as received. Standards of the test NPAH were prepared in either acetone or THF/acetonitrile. When these standards are stored in the refrigerator in the dark, all compounds are stable for at least 3 months at a concentration of approximately 10 pg of NPAH/mL. The labeled tracer 2-nitrofluorene (9-C-14)was purchased from California Bionuclear Corp. (Sun Valley, CA). The purity and activity of this tracer were determined both by the manufacturer and independently by this laboratory, both at the time of delivery and after 8 months of use. A reverse-phase HPLC chromatogram of the tracer showed a single peak on both occasions, and the specific activity, 3.6 mCi/mmol, was invariant over the time considered. The tracer was diluted with toluene to yield stock solutions of 70000 and 7000 disintegrations min-' mL-' and stored in a refrigerator. Samples. Authentic diesel exhaust particulates were donated both by D. Schuetzle and T. Riley (Ford Motor Co., Dearborn, MI) and J. L. Mauderly (Lovelace Biomedical Environmental Research Institute, Inc., Albuquerque, NM). In each case, the diesel engine used was a commercially available automobile engine that had been subjected to three complete EPA Federal Test Procedures (231,under a simulated light load. The Lovelace diesel particulate samples were furnished on 20 in. X 20 in. Pallflex glass fiber filter pads coated with Teflon (T-60 A-20, Pallflex Products Corp., Putnam, CT). Schuetzle and Riley also provided an aliquot of the soluble organic fraction (SOF) of a diesel particulate sample which had been characterized in their laboratory. They measured approximately 200 ppm of 1-nitropyrene/g of extract. This sample was used as received for testing the accuracy and precision of our procedure. SRM 1649Urban Dust (Organic)was purchased from the Office of Standard Reference Materials, National Bureau of Standards (Washington, DC). The stack ash sample from pulverized coal combustion was provided by Ralph Mitchell of the Battelle Columbus Laboratories (Columbus, OH) under an Electric Power Research Institute contract and was used as received. This sample is more highly enriched in organic matter than other stack ash samples and appears to be a "worst case" sample. Equipment: Extraction Apparatus. All particulate extractions were performed by sonicating the samples with a Sonifier Cell Disrupter, which was purchased from the Branson Sonic Power Co. (Danbury, CT). Samples were placed in standard medium-porosity filtering funnels (30, 60, or 350 mL capacity) and sonicated with the standard horn. No attempt was made to cool the filtering funnel. Isolation System. The semipreparative scale HPLC isolation system is an automated version of the manual system described previously (24). In this current version, a DP810 digital programmer and the associated rotary automatic stream selector valve, Model SSV-6 (Glenco Scientific, Inc., Houston, TX) were used to select the eluent from one of four reservoirs. A battery of miniature three-way Teflon solenoid valves (General Valve Corp., E. Havover, NJ, part no. 1-43-900),which was also controlled by the digital programmer, permitted convenient automated fraction collection. Gas Chromatograph, A Perkin-Elmer 3920 (Perkin-Elmer Corp., Norwalk, CT) gas chromatograph was used for all of the quantitations. The inlet was modified slightly to permit oncolumn injection of a sample. The instrument was equipped with a 3 m x 3.2 mm 0.d. (8 f t X l / * in. 0.d.) glass column packed with 3% (w/w) OV-17 on Gas Chrom Q (100/120 mesh), purchased from Applied Science Laboratories, Inc. (StateCollege, PA). The column exited at right angles to the injector, instead of the usual configuration, which is parallel to the injector, to permit connection to the thermal energy analyzer. The oven wall had to be pierced to permit this connection. The helium carrier gas flow rate was 30 mL/min. The injector temperature was 250 OC. The oven was programmed to hold the initial temperature of 60 "C for 4 min, increase it at 8 "C/min to 280 OC, and hold the final temperature for 16 min. Typically a 2-gL sample was injected onto the column. Thermal Energy Analyzer (TEA),A Thermo Electron TEA Model 543 analyzer, manufactured by the Thermo Electron COT., Analytical Instrument Division (Waltham, MA), was used for
quantitating NPAH. The interface temperature was fixed at 200 "C, while the pyrolyzer was optimized at 900 "C for NPAH. Oxygen was supplied to the reaction chamber to permit an equilibrium pressure (helium carrier gas plus oxygen flow under vacuum) of approximately 3.5 torr. Recovery Measurements. The recovery of seven standard nonlabeled NPAH was determined by spiking particulate samples with known quantities of the analyte and comparing the mass of the spike before and after the entire procedure. The recovery of the carbon-14 labeled tracer 2-nitrofluorene was determined by first adding 10 pL of the final 100 pL isolate to 10 mL of a scintillator cocktail prepared by dissolving 4 g of Omnifluor (New England Nuclear, Boston, MA) per liter of "Distilled in Glass" grade toluene. The activity of the resulting solution was then determined by liquid scintillation spectrometry and compared to that of the original radioactive spike. All measurements were taken over a 4- or 10-min interval at room temperature with the carbon-14 counting channel of a Tri-Carb Liquid Scintillation Counter, Model C-2425 (Packard Instrument Co., Downers Grove, IL). The calibrated automatic external standard option of the instrument was used to correct all sample counts for quenching. Special Glassware. All of the crude particulate extracts were taken to dryness with a standard rotary evaporator. The NPAH isolates were taken to dryness by use of both house vacuum and dry flowing nitrogen to remove solvent at ambient temperature (25). The dry isolate was quantitatively transferred to a 0.1 or 0.3 mL capacity volumetric flask (26) and brought to a final volume with dry flowing nitrogen. Sample Preparation: Extraction Procedure. (a) Diesel Particulates. One quarter of the 20 in. X 20 in. Pallflex filter was spiked dropwise with 1mL of radioactive tracer and/or nonradioactive spike solution, air-dried in a fume hood in subdued light for 1h, shredded, and transferred to a 350-mL medium-porosity fritted funnel. The filter was ultrasonically extracted three times with 250 mL of toluene (5 min per extraction), at a power setting corresponding to about 210 W. The resulting extracts were pooled, taken to dryness by rotary evaporation, and redissolved in 1 mL of methylene chloride. (b) Coal Stack Ash. Ten grams of coal stack ash was weighed into a crystallizing dish and covered with approximately 100 mL of methylene chloride. One milliliter of radioactive tracer and/or cold spike solution was added to the supernatant, and the entire contents were ultrasonically agitated for 30 s. The solvent was permitted to evaporate overnight, and the spiked stack ash was transferred to a 60-mL medium-porosity fritted funnel. The sample was then ultrasonically extracted four times with 25 mL of toluene (3 min per extraction), under the same conditions as the diesel particulate pad. The extracts were then pooled and treated in the same manner as the diesel particulate extract. The final sample volume was 0.3 mL. ( c ) Urban Dust. One gram of urban dust was spiked as described for coal fly ash. The spiked dust was then transferred to a 30-mL medium-porosity fritted funnel and ultrasonically extracted four times with 20 mL of toluene (3 min per extraction) as described above. The pooled extracts were then taken to dryness as described for the diesel particulates. The resulting residue, which contained a significant quantity of black material, was then redissolved in a total of 50 mL of dimethyl sulfoxide (Me2SO). One hundred milliliters of water and 1g of salt were added to the MezSO solution, and the mixture was partitioned with pentane, as described in Natusch and Tomkins (27). One hundred milliliters of benzene was added to the final pentane extract, which was then taken to dryness by rotary evaporation. The residue was then redissolved in 1mL of methylene chloride. (d) Diesel Particulate SOF. The SOF sample was diluted to exactly 1 mL with methylene chloride, without further preparation. HPLC Fractionation. The NPAH-enriched fraction was defined by using the solvent volume required to elute the six components 2-nitronaphthalene, 3- and 4-nitrobiphenyl, 2nitrofluorene, 9-nitroanthracene, and 1-nitropyrene. A mononitrated PAH-enriched fraction is readily eluted from the Zorbax aminosilane HPLC column with 10% (vol/vol) methylene chloride in hexane, collected, taken to dryness, and redissolved in 100 pL of methylene chloride or THF. The column was later cleaned, flushed, and reequilibrated, as detailed elsewhere (28).
ANALYTICAL CHEMISTRY, VOL. 56, NO. 4, APRIL 1984
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2-NITAOFLUORENE v 9-NITAOTHRACENE 0
I
I 1 I I1111
I
-
-
I IIlllL
783
0
-
3 0
IO
20 30 TIME (rnin)
40
Figure 2. Profiles of a crude diesel particulate extract (A) and a purified isolate (B) from the same sample, using the GCITEA.
13H-dibenzo[a]carbazole,benzanthrone, and p-benzoquinone. The TEA did not produce a detectable response to any of these compounds, thereby demonstrating discrimination against aromatic amines, azaarenes, ketones, and phenols. These results, when combined with those of Yu (22),demonstrate the selectivity of the TEA toward nitro-bearing species and the ability to discriminate against potential interferences which may be found in real-world sample extracts. While other common gas chromatographic detectors, such as the nitrogen-phosphorus detector (NPD), may well exhibit greater sensitivity for NPAH, they also demand a much cleaner NPAH-enriched isolate. The TEA provides both g o d sensitivity and excellent selectivity. When flash vaporization was used to introduce the sample into the analytical GC column, fairly broad NPAH peaks with considerable tailing were observed, probably due to adsorption of the NPAH onto the injector wall. Sharp, clean peaks with minimal tailing were obtained when the flash injection port was replaced with a simple on-column injector. The use of a heated injector (250 "C), however, did not appear to produce significant degradation of the smaller-ring NPAH. The high selectivity of the TEA suggested that the NPAH in a crude particulate extract could be determined directly by using the gas chromatograph/thermal energy analyzer (GC/TEA) without any purification. This possibility was not realized for the particulate samples examined. In each case, the chromatogram of the crude extract exhibited an undulating base line and broad, poorly formed peaks, as shown in Figure 2A. The retention index data given in Table I suggest that these features were probably due to poor resolution of NPAH from complex multifunctional polar nitrated species also produced by the combustion source. Purification of the extract was clearly essential for obtaining the required specificity for simple NPAH species. We elected to use a semipreparative scale aminosilane HPLC column (amino groups chemically bonded to silica) because this was a general purpose column which would tolerate a wide variety
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ANALYTICAL CHEMISTRY, VOL. 56, NO. 4, APRIL _ _ I I _ _
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Table I. Relative Retention Indexes for Nitro-Bearing Compounds
5
re1 retention time w c
compound 5-nitroindan 1aitronapht halene 5-nitroquinoline 2-nitronaphthalene 6-nitroquinoline 3-nitrobiphenyl 4 -nitrob iphen yl 8-nitroquinoline 1,S-dinitronaphthalene 1,3-dinitronaphthalene 2,2’-dinitrobiphenyl 2 -nit rof luorene 9-nitroanthracene 3-nitro-9-fluorenone 1-methyl-9-nitroanthracene 1-methyl-10-nitroanthracene 1,8-dinitronaphthalene 9-methyl-10-nitroanthracene 3-nitrofluoranthene 1-nitropyrene (3-nitropyrene ) 2,7-dinitrofluorene
0.54 0.59 0.59 0.60 0.63 0.67 0.68 0.68 0.75 0.75 0.78 0.79
16
8
W
0.80 0.83 0.84 0.84 0.87 0.96 1.oo 1.07 1.22 >1.5 >1.5 >1.5 >1.5
6-nitrochr ysene
b-
a Relative to 1-nitropyrene. 3% w/w OV-17 on Gas Chrom Q (100/120 mesh). Other conditions are given in text. One test for each compound.
HEXANE
40% lv/v) M e C l /HEXANE
Me CI2/HEXANE
+I-------
METHYLENE CHLORIDE
HEXANE
~
I
A
N
GI
> ’ 31
0
20
40
60
80
7
0.80
6-nitrobenzo[ alpyrene 3-nitroperylene 2,4,7-trinitro-9-fluorenone 1,6-dinitropyrene
40 70 I v/v)
&!( 5
400
120
440
TIME i m i n )
Flgure 3. Isolation profiles from a diesel particulate extract (A) and a seven-component NPAH standard (B) by using semipreparative scale HPLC. Standard peaks are 2-nitronaphthalene (l),3-nitrobiphenyl (2), 4-nitrobiphenyl (3), 2-nitrofluorene (4), 9-nitroanthracene (9,l-nitropyrene (6), and 2,7dinitrofluorene (7).
of samples and small variations in the water content of the solvent (28,29). I t permitted successful isolation of a fraction which contained simple NPAH, PAH, and certain simple ketone-bearing species, Figure 3 shows the semipreparative scale HPLC chromatograms of both an NPAH-containing standard and a diesel particulate matter extract. The NPAH
-
2
+
0
40
eo
30
40
TIME imin)
Figure 4. GCITEA profiles of purified NPAH isolates obtained from (a) a characterized diesel particulate SOF and (b) a diesel particulate sample. Labeled peaks are 2-nitronaphthaiene (I), 3-nltrobiphenyi (2), 4-nitrobiphenyi (3), 2-nitrofluorene (4), 9-nitroanthracene (5), 1methyl-10-nitroanthracene (6), 9-methyl-10-nitroanthracene (7), 1nitropyrene (a), and 2,7-dinitrofiuorene (9).
fraction cut points were chosen to include most of the mononitro PAH. Figure 2 compares the GC/TEA chromatograms of the NPAH-enriched fraction prepared by HPLC of a diesel particulate matter extract with that of the crude extract. The fraction is clearly suitable for GC/TEA quantitation and identification of the NPAH because potential interfering nitro-substituted species such as nitroquinolines, nitro ketones, and nitrophenols were successfully separated from the NPAH by the HPLC step. This separation step provides nitrochemical class (i.e,, mononitro PAH) specificity to the GC/ TEA determination. Figure 4 compares the GC/TEA chromatograms for the NPAH fractions isolated from the diesel particulate extract and the Ford SOF with a seven-component NPAH standard. The two sample chromatograms are strikingly similar and reflect the similarity in the type of engine tested, loading, and test cycle employed. Qualitative identifications of NPAH present were made by using the relative retention time data listed in Table I. Triplicate determinations of 1-nitropyrene in the Ford SOF yielded a mean value of 165 ppm l-nitropyrene in the SOF (standard deviation, 20 ppm). The agreement between our mean value and the stated value of 200 ppm (precision not known) was considered acceptable. The detection limit for this sample, estimated a t twice the noise level, was 21 ppm of 1-nitropyrene in the SOF. Concentrations of 165 ppm 9-nitroanthracene, 135 ppm 9methyl-10-nitroanthracene, 224 ppm 1-methyl-10-nitroanthracene, and 27 ppm 3-nitrobiphenyl in the SOF were also determined with similar precision. The NPAH fraction of the SOF was subjected to highresolution mass spectrometry, employing a temperatureprogrammable probe, in order to confirm the existence of
ANALYTICAL CHEMISTRY, VOL. 56, NO. 4, APRIL 1984
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Table 11. Recoverv Data for NPAH Spiked onto Various Particulate-Matrices recovery, % concn diesel of spike, fly urban particcompoundspiked ppm ash dust ulate Z-nitronaphthalene 10 36 84 1 58 0 0 3-nitrobiphenyl 10 74 90 1 83 65 18 __ 4-nitrobiphenyl 10 82 67 1 96 67 10 2-nitrofluorene 10 91 77 1 100 100 12 88 100 2-nitrofluorene 20 (9-14C)tracer 4 97 100 78 0.1 100 9-nitroanthracene 10 57 55 1 76 40 25 1-nitropyrene 10 33 80 1 99 14 30
‘O’
40
20
30
40
TIME (mtn)
Figure 5. GC/TEA profiles of purified NPAH isolate obtained from (a)
a coal-fired power plant stack ash and (b) NBS 1649 Urban Dust. Peak identifications are the same as those in Figure 4.
NPAH species identified by the GC/TEA. The existence of a t least one nitropyrene species and a t least one methyl nitropyrene isomer was confirmed. Other NPAH could not be detected a t the sensitivity of the mass spectrometer, which was considerably less than that of the TEA. This observation underscores the difficulties in obtaining independent confirmation of identities based on retention time data and highly sensitive and selective GC detectors. Examination of the diesel particulate sample extracted in our own laboratory enabled the mass of five NPAH to be related to the particulate as a weight/weight concentration. A concentration of 10 ppm of 1-nitropyrene in diesel exhaust particulates was observed for the Lovelace sample shown in Figure 4. This value was in good agreement with that determined by Gibson (30),which was 8.0 f 2.4 ppm (mean f standard deviation, n = 4). The approximate sensitivity observed a t twice the noise level was 1ppm of 1-nitropyrene in the diesel particulate sample. Approximately 500 mg of particulate matter was needed for this measurement. The concentrations of 3-nitrobiphenyl, 9-nitroantracene, 1methyl-10-nitroanthracene, and 9-methyl-10-nitroanthracene were 1, 8, 10, and 2 ppm, respectively. A single particulate sample could be processed every 8 h. The chromatograms of NPAH observed in a coal stack ash and an urban dust sample are given in Figure 5 and are contrasted with a seven-component NPAH standard. The cluster of peaks observed in the gas chromatogram of the stack ash sample eluted in the region defined by three- and four-ring NPAH, as shown in Table I. The NPAH 1-nitropyrene appeared to be present at a concentration of 0.2 ppm in the stack ash, with a detection limit of 0.05 ppm. This result is 60 times lower than that for diesel particulates. The principal differences between the determinations of NPAH in fly ash and diesel particulates were the mass of sample taken (10 g vs. 0.5 g) and the final volume of isolate (300 ILLvs. 100 HL). The stack ash assay was therefore about 60 times more sensitive than that for the diesel particulates.
The almost-featureless chromatogram shown in Figure 5 for the urban dust demonstrates much lower concentrations of simple NPAH in this sample, even though the recovery measurements (discussed below) show that native NPAH, if present, would be detected, a t least at the 1 ppm level. Some nitro-bearing constituents were eluted with 40% (vol/vol) methylene chloride in hexane. However, these materials are probably more polar than the NPAH considered for the other particulate samples, and their chemical nature is less clearly understood. The sensitivity of this measurement was approximately that observed for stack ash. The total mononitrated PAH (MNPAH) content of a given sample may be helpful in judging the relative potential hazard of a particular material. A crude estimate of total MNPAH is possible with the GC/TEA system because many MNPAH exhibit an identical linear response (see Figure 1). Calculations of this nature usually permit the total MNPAH to be expressed as the weight/weight concentration of a single species. If 1-nitropyreneis chosen as the reference compound, the total MNPAH content will appear high but will also represent a conservative value. Accordingly, if the total MNPAH content of the diesel particulate SOF and particulate matter extracts are estimated as 1-nitropyrene, the values are 800 and 50 ppm, respectively. These data agree respectably with the sum of the concentrations of the five major identified peaks, which are 710 and 30 ppm, respectively. The NBS Urban Dust is estimated to contain 2 ppm NPAH. A similar estimate for coal stack ash, based on 1-nitropyrene, yields 2 ppm. Fly ash, even in this “worst case” situation, appears to contain considerably less NPAH than diesel particulate matter. The accuracy of our analytical procedure was examined by using a series of spike recovery studies. Recoveries of NPAH in three sample matrices were determined a t two different concentrations by using both a radiolabeled tracer and nonradioactive spikes which represented two- to four-ring NPAH. The precautions given in the Experimental Section promoted uniform distribution of the spike, even in several grams of solid (31),and minimal photodegradation of the test compounds. Table I1 summarizes the recovery for the various spikes and the samples tested. While the recovery data were quite satisfactory for the stack ash and urban dust samples, severe losses of the nonlabeled spikes were observed when they were applied to diesel particulate matter at low (- 1 ppm) concentrations. This effect also has been observed by others (32). The recovery of labeled tracer applied to diesel particulates a t low concentrations exceeded 85% when the radioactivity was measured. However, we did not observe a corresponding
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strong response for the tracer when its recovery was measured by GC/TEA as a concentration of 2-nitrofluorene. It is strongly suspected that the tracer degraded on the diesel particulate surface to a more polar oxidized form which could not be distinguished from the parent tracer by liquid scintillation spectrometry. Benzo[a]pyrene will behave similarly with the surface conditions encountered on some stack ash samples (28). This problem with the labeled nitro-PAH tracer was not observed on stack ash or urban dust samples. Our experiences illustrate the necessity of using both radiolabeled tracers and cold spikes when evaluating NPAH recoveries.
ACKNOWLEDGMENT The authors express their appreciation to G. L. Glish and E. H. McBay for performing the high-resolution mass spectrometry reported in this paper. The authors express their thanks to D. Schuetzle and T. L. Riley (Analytical Sciences Department, Ford Motor Co., Dearborn, MI) and J. L. Mauderly, (Lovelace Biomedical Environmental Research Institute, Albuquerque, NM) for their gifts of the characterized soluble organic fraction and the diesel particulates used in this work. The methylated nitroanthracene isomers were graciously provided by P. Ruehle and W. Duncan (Midwest Research Institute, Kansas City, MO). LITERATURE CITED Pitts, J. N.; Van Cauwenberghe, K. A.; Grosjean, D.; Schmid, J. P.; Fitz, D. R.; Beiser, W. L.; Knudson, G. B.; Hynds, P. M. Sclence 1978, 202,515-519. Pederson, T. C.; Siak, J.-S. J. Appl. Toxicol. 1981, 1, 54-61. Schuetzie, D.; Lee, F. S.4.; Prater, T. J.; Tejada, S. 8. Int. J . Envlron. Anal. Chem. 1981, 9 , 93-144. Nielsen, T. Nitro Derivatives of Polynuclear Aromatlcs: Formation, Presence and Transformatlon in Stack and Exhaust Gases and in the Atmosphere (Riso-13-455); Rlso National Laboratory: Roskiide, Denmark, 1981. Nielsen, T. Anal. Chem. 1983, 55,286-290. Nielsen, T.; Seitz, B.; Hansen, A. M.; Keidlng, K.; Westerberg, B. I n "Polynuclear Aromatic Hydrocarbons: Formation, Metabolism, and Measurement"; Cooke, M., Dennis, A. J., Eds.; Battelle Press: Columbus, OH, 1983; pp 961-971. Rappaport, S. M.; Wang, Y. Y.; Wei, E. T.; Sawyer, R.; Watkins, D. E.; Rapoport, H. R. Envlron. Sci. Technol. 1980, 14, 1505-1509. Xu, X. B.; Nachtman, J. P.; Jin, 2. L.; Wel, E. T.; Rappaport, S. M.; Burlingame, A. L. Anal. Chlm. Acta 1982, 136, 163-174. Ramdahl, T.; Becher, G.; Bjorseth, A. Envlron. Scl. Technol. 1982, 16, 861-865. Rappaport, S. M.; Jin, 2. L.; Xu, X. B. J. Chromatogr. 1982, 240, 145-1 54. Morita, K.; Fukamachi, K.; Tokiwa, H. Bunseki Kagaku 1982, 3 1 , 255-275. MacCrehan, W. A.; May, W. E. "Abstracts of Papers", 186th Natlonal Meeting of the American Chemical Society, Washlngton, DC; American Chemical Society: Washington, DC, 1983; Analytical Chemistry Division, Paper 91. Schuetzle, D.; Riley, T. L.; Prater, T. J.; Harvey, T. M.; Hunt, D. F. Anal. Chem. 1982, 5 4 , 265-271. Newton, D. L.: Erickson, M. D.; Tomer, K. B.; Pellizzarl, E. D.; Gentry, P.; Zweldinger, R. B. Envlron. Sci. Technol. 1982, 76, 206-213. Paputa-Peck, M.; Hampton, C.; Marano, R.; Schuetzle, D.; Rlley, T. L.; Prater, T. J.; Skewes, L. M.; Ruehle, P.; Bosch, L.; Duncan, W. Anal. Chem. 1983, 55, 1946-1954.
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RECEIVED for review October 28,1983. Accepted January 16, 1984. This work was sponsored by the Electric Power Research Institute under Interagency Agreement DOE No. RTS77-58, EPRI No. 1057-1under Union Carbide Corporation Contract W-7405-eng-26 with the US. Department of Energy. M.E.R. acknowledges participation in the Oak Ridge Associated Universities Summer Program at Oak Ridge National Laboratory during the course of this work. This report was prepared by Oak Ridge National Laboratory, operated by Union Carbide Corporation (Union Carbide), on behalf of the U.S. Department of Energy (DOE), as an account of work sponsored by the Electric Power Research Institute, Inc. (EPRI). Neither EPRI, members of EPRI, Union Carbide, DOE, the U S . Government, nor any persons acting on their behalf: (a) makes any warranty or representation, express or implied, with respect to the information contained in this report; or (b) assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information disclosed in this report. Organization(s) that prepared this report: Oak Ridge National Laboratory.
