Analytica Chimica Acta 501 (2004) 71–78

Measurement of semi-volatile azaarenes inairborne particulate and vapor phases

Hung-Yu Chena,∗, Martin R. Prestonb

a Department of Oceanography, National Taiwan Ocean University, 2 Pei-Ning Road,Keelung 202, Taiwan, ROC

b Department of Earth and Ocean Sciences, University of Liverpool,4 Brownlow Street, Liverpool L69 3GP, UK

Received 23 July 2003; received in revised form 8 September 2003; accepted 9 September 2003

Abstract

In the atmosphere, exchanges between the gas and particle phases has a profound influence on the removal processes and residence timesof semi-volatile compounds. This study describes analytical procedures for the reliable quantitation of both gas and particle phase azaarenes(two-, three- and four-rings). Samples of particulate material were collected on the glass fiber filters and gas phase material on polyurethanefoam plugs. Azaarene compounds were isolated utilizing an acid/base partition method. Isolated azaarenes compounds were then characterizedand quantified using gas chromatography with mass spectrometry (GC/MS). The analytical method described in this paper is the first procedurefor the simultaneous determination of gas and particle phase azaarenes and allows 47 azaarene compounds to be reliably quantified despitethe complexity of urban aerosols.© 2003 Elsevier B.V. All rights reserved.

Keywords:Azaarenes; Gas and particle phases separation; Acid/base partitioning method; Semi-volatile organic compounds; Polyurethane foam

1. Introduction

Azaarenes are classified asN-heterocycles (Fig. 1) whereone of carbon atoms in the structure of polycyclic aromatichydrocarbons (PAHs) is replaced by nitrogen[1] and theyare known to be structural elements of fossil fuels[2]. LikePAHs, azaarenes are also semi-volatile under ambient tem-perature[3], and have significant proportions in both vaporand solid phases. The presence of the nitrogen atom alsomeans that azaarenes are more soluble in water than PAHs[4]. Sources of azaarenes are largely analogous to thoseof anthropogenically derived PAHs and include vehicle ex-hausts, coal derived liquids[5], bitumen spreading, and to-bacco smoking[6]. The distributions of polycyclic aromaticcompounds (PACs) in the environment has been the sub-ject of growing concern because they are known mutagensand/or carcinogens. Human exposure to azaarenes occursprimarily through inhalation of polluted air and by ingestion

∗ Corresponding author. Tel.:+886-224620951; fax:+886-224621047.E-mail address:hychen@mail.ntou.edu.tw (H.-Y. Chen).

of food and water contaminated with combustion product[7].

Recently, there has been increased interest in analyticaldevelopment for a variety of various derivatives of PAHsuch as hydroxyl-PAHs, nitro-PAHs, oxygenated-PAHs andazaarenes[8]. Azaarenes have become widespread in the en-vironment through the extensive use of fossil fuels and havebeen found in a number of environmental media, includ-ing urban aerosols[9–11], marine and freshwater sediments[12,13], and crude oil and petroleum products[6].

High volume samplers equipped with polyurethane foam(PUF) have became a standard sampling method for theambient air monitoring of semi-volatile organic compounds(SVOCs)[14,15]. Due to the flow characteristics and trap-ping efficiency, large volumes of air can be passed throughand volatile organic compounds can be adsorbed on PUFcartridges[16]. During the sampling period, the particulatephase materials are trapped on the filter and the gaseousphase passes through the filter to be subsequently absorbedby PUF. Samples collected on PUF are typically extractedby continuous Soxhlet extraction[16].

0003-2670/$ – see front matter © 2003 Elsevier B.V. All rights reserved.doi:10.1016/j.aca.2003.09.017

72 H.-Y. Chen, M.R. Preston / Analytica Chimica Acta 501 (2004) 71–78

Quinoline Isoquinoline 7,8-Benzoquinoline

Acridine Phenanthridine 5,6-Benzoquinoline

2-Azapyrene Azachrysene Benzacridine

N N

NNN

N

NN

N

Fig. 1. Structures of some two-, three- and four-ring azaarenes.

Several different analytical methods have been applied toisolate azaarenes from organic extracts. For example, alumnacolumns and a variety of different eluants have been usedto isolate and fractionate azaarenes from solvent extracts[10,17,18]. Grimmer and Naujack[6] chromatographed or-ganic extracts on SP-Sephadex columns, allowing azaarenesto eluted and separated by different solvents. Other workershave utilized acid/base partition to isolate azaarenes fromorganic extracts[9,19,20]. The advantages of acid/base par-tition are first, that this method is operationally simple. Theprinciple of this method is to use acid to isolate azaarenesfrom an organic mixture then, after increasing pH to 14, toback-extract the azaarenes into solvent. Second, it does notneed large volumes of complex solvent mixtures and reducesanalysis times. Finally, it has been shown that the recover-ies are good for two-, three- and four-ring azaarenes. How-ever, the main disadvantage is that recoveries for five-ringazaarenes are low but these compounds are not particularlysignificant in the urban atmosphere[21].

Several chromatographic analytical or separation methodshave been documented for the characterization and quan-tification of azaarenes. These include high-performanceliquid chromatography (HPLC)[22,23], and thin-layerchromatography (TLC)[19]. Gas chromatography (GC)has been successfully applied with flame ionization detec-tion (FID) [6,9,18], nitrogen–phosphorus detection (NPD),inductively coupled plasma (ICP), and electron capture de-tection (ECD)[24]. GC with mass spectrometry (GC/MS)as a specific ion detection method is the most sensitive andpopular analytical method for azaarenes[25,26].

To date virtually all published work has focused on theparticulate azaarene compounds. However, azaarenes behaveas semi-volatile compound in the ambient atmosphere. So toform a reliable picture of the distribution of such compoundsin the atmosphere, it is necessary to understand not only theparticulate phase, but also the vapor phase concentration.This study describes an improved analytical method for the

analysis of trace levels of azaarene present as particulate andvapor phases in urban aerosols.

2. Experimental

2.1. Sample collection

All the samples were collected by using PUF sampler(GPS-1 PUF sampler; General Metal Works, OH, USA).An pre-ashed 4 in. (102 mm) diameter glass fiber filter wasweighted and loaded on the filter unit. Two solvents (seedetails further) cleaned PUF plugs (50 mm i.d.; GeneralMetal Works) were put into the glass cartridge then cov-ered by a lower canister and screwed together with filterholder support. Finally, the filter part was screwed togetherwith PUF plugs part. During the sampling period, the par-ticulate azaarenes were trapped on the glass fiber filter andthe vapor phase azaarenes were adsorbed onto the PUFplugs.

The ambient temperature is a key factor for gas/particlepartitioning behavior and the temperature variation proba-bly reaches±5◦C at the sampling site during a day–nightcycle [3]. If the temperature goes up, azaarenes will escapefrom the particle surface and be captured by PUF plugs. Sowhilst re-partitioning may happen within the sample, thisis an unavoidable problem. Estimates of the significance oftemperature variations can be calculated[11].

The sampling period was about 7 days for each sample(the ambient temperatures varied between 15 and 25◦C).The sampling system was operated at 0.28 m3 min−1 for144 h, so, the total sampling air volume was approximately2419 m3 of air. After sampling, the filter was freeze-driedand weighed. All filters and PUF plugs were individu-ally covered with pre-ashed aluminum foil individuallyand stored at−24◦C in a freezer before extraction. To-tal suspended particle (TSP) values were obtained fromthe difference of sample weight gained before and aftersampling.

2.2. Solvent extraction

To avoid any artificial and air pollution in the labora-tory, the Soxhlet extraction and separation procedures wereconducted in a fume cupboard operating within a positivepressure clean room. Before sample extraction, the wholeapparatus was cleaned by distilled dichlormethane (DCM)for 2 h to reduce the occurrence of contaminant.

The filter or PUF plug samples were put into the innertube of the Soxhlet apparatus directly whereas the solidsamples were folded and put into a thimble before inser-tion. In both cases 100�l of 5 mg l−1 internal standard,[2H9]acridine (acridine-d9; Cambridge Isotope Labora-tories, UK; purity = 98%) was spiked into the sample.Therefore, the concentration of the specific azaarene com-pound can be calculated by the response factor relative to

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the internal standard on GC/MS. The sample was extractedusing about 200 ml of DCM at an extraction rate of ca.5 min per cycle for at least 18 h. Care was taken to avoidboiling the solvent more vigorously than necessary, as somevolatilization of the lighter two-ring species (quinoline andisoquinoline) have been noted previously[20,21].

After extraction, the organic extract was reduced in vol-ume to about 0.5 ml using rotary evaporation at 30◦C. Then,the extract was stored in a freezer at a temperature of under−24◦C before required for the acid/base partition.

Table 1Mass fragment ions of peaks in total ion chromatogram

Compound no. Abbreviation Confidence levela m/z of mass fragment ions detectedb

1 Q S 129(m) 102(b) 75(d)2 IsoQ S 129(m) 102(b) 75(d)3 2-C1Q S 143(m) 115(c)4 8-C1Q S 143(m) 115(c)5 C1Q 01 M 143(m) 115(c)6 C1Q 02 M 143(m)7 6-C1Q S 143(m)8 C1Q 03 M 143(m)9 C2Q 01 M 157(m) 142(a) 115

10 2,6-C2Q S 157(m) 142(a) 11511 C2Q 02 M 157(m) 142(a) 11512 C2Q 03 M 157(m) 142(a) 115 7813 C2Q 04 M 157(m) 142(a) 115 7814 C2Q 05 M 157(m) 142(a) 115 7815 C2Q 06 M 157(m) 142(a) 11516 C2Q 07 M 157(m) 142(a) 11517 C2Q 08 M 157(m) 142(a) 11518 C2Q 09 M 157(m) 142(a) 11519 C2Q 10 M 157(m)20 C2Q 11 M 157(m) 142(a) 11521 C3Q 01 M 171(m) 156(a) 144(b)22 C3Q 02 M 171(m) 156(a) 12823 C3Q 03 M 171(m) 156(a) 12824 C3Q 04 M 171(m) 156(a) 144(b) 12825 C3Q 05 M 171(m) 12826 C3Q 06 M 171(m) 156(a) 12827 C3Q 07 M 171(m) 12828 C3Q 08 M 171(m) 156(a) 12829 B(h)Q S 179(m) 151(c) 90 7630 A S 179(m) 151(c) 90 7631 Phen S 179(m) 151(c) 90 7632 B(f)Q S 179(m) 151(c) 90 7633 MA 01 M 193(m) 165(c) 9734 MA 02 M 193(m) 165(c) 97 8435 MA 03 M 193(m) 165(c) 97 8436 MA 04 M 193(m) 165(c) 9737 MA 05 M 193(m) 165(c) 8438 MA 06 M 193(m) 165(c) 9739 9-MA S 193(m) 165(c) 151 9740 MA 07 M 193(m)41 Azapy01 M 203(m) 176(b) 102 8842 Azapy02 M 203(m) 176(b) 102 8843 Azapy03 M 203(m) 176(b) 102 8844 Azapy04 M 203(m) 176(b) 102 8845 2-Azapy S 203(m) 175(b)46 Azachry01 M 229(m)47 2-Azachry S 229(m)

a Confidence level: S, characterized by the standard; M, only from mass spectrum obtained.b Fragment ions: m,M+; a, [M − CH3]+; b, [M − CHN]+; c, [M − CNH2]+; d, [M − 2(CNH)]+.

2.3. Acid/base partitioning

Azaarenes are basic compounds, so this property can beused to separate these compounds from the neutral PAHs[22]. In this study, about 1 ml of 4 M HCl was added tothe vial containing the DCM extract and shaken for 15 min.The upper (acid) layer containing azaarenes was transferredto a pre-cleaned screw-topped Pyrex vial and covered bypre-ashed foil. The DCM/acid partition was repeated twicemore, and the acidified aqueous layers combined.

74 H.-Y. Chen, M.R. Preston / Analytica Chimica Acta 501 (2004) 71–78

The vial was then put into an ice bath, and 6 M NaOHwas slowly added to the tube until a piece of pH paperbecame blue which was about pH 14. Then, 2 ml of DCMwas added to the tube and shaken for 15 min, after whichthe bottom, DCM layer, was quantitatively transferred toa new pre-cleaned 7 ml vial. The back-extraction was re-peated twice and DCM was collected in the same vial.Both acid and base reagents were diluted with Milli-Qwater.

Finally, the DCM extract was then passed through aNa2SO4 (anhydrous sodium sulfate anhydrous) column(100 mm× 6 mm) to dry the sample extract. The sampleswere stored at−24◦C until GC or GC/MS analysis. Beforeinjection, the solvent in the vial was removed by gentle blow-ing down to dryness under purified nitrogen, and then 100�lDCM with 5 ppm quantitative standard, 3-aminoquinoline

Fig. 2. Typical GC/MS chromatograms of azaarenes trapped on: (a) glass fiber filter; (b) PUF plug. The abbreviations of the number of peak arecorresponded toTable 1. Time scales in minutes.

(Sigma, St. Louis, MO, USA; purity= 98%), was added tothe vial. The quantitative standard was used to check therecovery of the internal standard (d9-acridine) through thewhole analytical procedure. Finally, 0.4�l of the samplewas injected into the GC column.

2.4. GC/MS

Samples were chromatographically separated using aBPX-5 column (fused silica; 5% phenyl/methylsiliconebonded phase; SGE, Sydney, Australia). The column wasprogrammed from 60 to 300◦C at 10◦C min−1, thenmaintained at 300◦C for 10 min in a HP 5890A GCsystem.

After chromatographic separation, the sample was intro-duced into a VG TS250 double focusing magnetic sector

H.-Y. Chen, M.R. Preston / Analytica Chimica Acta 501 (2004) 71–78 75

mass spectrometer. The emission current was 0.50 mA at70 eV, and the temperature of the ion source was 250◦C.Data acquired from GC/MS analysis was processed andsaved on one of a pair of Digital Equipment CorporationVAX 2000 workstations.

Peaks with a signal-to-noise (S/N) ratio smaller than 20could not reliably integrated. If S/N ratio between 10 and20, the peaks were identified but not quantified. Once thecompounds were identified, selected ion monitoring (SIM)

Table 2Isomers routinely determination using GC/MS analysis

Compound no. Abbreviation Compound m/z Retention time (min:s)

1 Q Quinoline 129 9:292 IsoQ Isoquinoline 129 9:503 2-C1Q 2-Methylquinoline 143 10:294 8-C1Q 8-Methylquinoline 143 10:375 C1Q 01 Methylquinoline/methylisoquinoline isomer 143 10:496 C1Q 02 Methylquinoline/methylisoquinoline isomer 143 11:007 6-C1Q 6-Methylquinoline 143 11:118 C1Q 03 Methylquinoline/methylisoquinoline isomer 143 11:499 C2Q 01 Dimethylquinoline/dimethylisoquinoline isomer 157 11:50

10 2,6-C2Q 2,6-Dimethylquinoline 157 12:0711 C2Q 02 Dimethylquinoline/dimethylisoquinoline isomer 157 12:2312 C2Q 03 Dimethylquinoline/dimethylisoquinoline isomer 157 12:3313 C2Q 04 Dimethylquinoline/dimethylisoquinoline isomer 157 12:3914 C2Q 05 Dimethylquinoline/dimethylisoquinoline isomer 157 12:4815 C2Q 06 Dimethylquinoline/dimethylisoquinoline isomer 157 13:5316 C2Q 07 Dimethylquinoline/dimethylisoquinoline isomer 157 13:0017 C2Q 08 Dimethylquinoline/dimethylisoquinoline isomer 157 13:0918 C2Q 09 Dimethylquinoline/dimethylisoquinoline isomer 157 13:1719 C2Q 10 Dimethylquinoline/dimethylisoquinoline isomer 157 13:2420 C2Q 11 Dimethylquinoline/dimethylisoquinoline isomer 157 13:3921 C3Q 01 Trimethylquinoline/trimethylisoquinoline isomer 171 13:2922 C3Q 02 Trimethylquinoline/trimethylisoquinoline isomer 171 13:3623 C3Q 03 Trimethylquinoline/trimethylisoquinoline isomer 171 13:4824 C3Q 04 Trimethylquinoline/trimethylisoquinoline isomer 171 13:5525 C3Q 05 Trimethylquinoline/trimethylisoquinoline isomer 171 14:0526 C3Q 06 Trimethylquinoline/trimethylisoquinoline isomer 171 14:1827 C3Q 07 Trimethylquinoline/trimethylisoquinoline isomer 171 14:3028 C3Q 08 Trimethylquinoline/trimethylisoquinoline isomer 171 14:4629 B(h)Q Benzo(h)quinoline 179 16:5930 A Acridine 179 17:0831 Phen Phenanthridine 179 17:2532 B(f)Q Benzo(f)quinoline 179 17:4933 MA 01 Methylated three-ring azaarene isomer 193 17:3734 MA 02 Methylated three-ring azaarene isomer 193 17:4735 MA 03 Methylated three-ring azaarene isomer 193 18:0636 MA 04 Methylated three-ring azaarene isomer 193 18:1337 MA 05 Methylated three-ring azaarene isomer 193 18:2638 MA 06 Methylated three-ring azaarene isomer 193 18:3939 9-MA 9-Methylacridine 193 19:0040 MA 07 Methylated three-ring azaarene isomer 193 19:0741 Azapy01 Azapyrene/azafluoranthene isomer 203 20:0842 Azapy02 Azapyrene/azafluoranthene isomer 203 20:2143 Azapy03 Azapyrene/azafluoranthene isomer 203 20:2644 Azapy04 Azapyrene/azafluoranthene isomer 203 20:5945 2-Azapy 2-Azapyrene 203 21:1946 Azachry01 Azachrysene/benzacridine isomer 229 23:1147 2-Azachry 2-Azachrysene 229 24:26

I.S. Internal standard d9-Acridine 188 17:05Q.S. Quantitative standard 3-Aminoquinoline 144 15:11

was used for routine analysis. Azaarenes were identified bycomparing peak retention times and [(M + 1)+]/[M+] ionreference standards. The real sample concentrations werecalculated from the peak area ratio between the sample andthe internal standard multiplied by the response factor be-tween reference standard and internal standard on GC/MS.In case the commercialized reference standard cannot befound, the response factor of the same group compound wasused.

76 H.-Y. Chen, M.R. Preston / Analytica Chimica Acta 501 (2004) 71–78

3. Results and discussion

3.1. Identification of azaarene compounds in urbanaerosol sample

The identification of azaarene compounds were referredto the ion chromatograms for the selected standards, orsearched by NIST library. All mass spectra of peaks in totalion currents (TICs) were analyzed according to the identi-fied method by Nito and Ishizaki[26].

Table 1shows confidence levels andm/z of mass frag-ments in mass spectra of each peak of azaarenes. If the massfragment of individual compound was characterized by com-paring with their standard material, this compound was con-sidered credible and marked as S. If the mass fragment ofindividual compound was characterized only by comparingwith the NIST library, this compound was represented as M.Fragment ions corresponding to [M−CH3]+, [M−CHN]+,[M − CNH2]+, and [M − 2(CNH)]+ showed loss of CH3,CHN, CNH2, and 2(CNH), respectively.

3.2. GC/MS retention time and response factors

Fig. 2a and bshow that the chromatograms of TIC forparticulate and vapor phase azaarenes from the urban atmo-sphere. The fractions of three-ring (benzoquinolines, acri-dine, phenanthridine and methylated three-ring azaarenes)and four-ring compounds (azapyrenes and azachrysenes)give a significant variation between particulate and vaporphase.

Table 4Reproducibility of real sample analysis

Sample no. Q+ IsoQ∑

MQ∑

DMQ∑

TMQ∑

BBAP∑

MA∑

Azapy∑

Azachry Two-ring Three-ring Four-ring

Sample 1a

Mean (ng m−3) 0.6524 0.6960 1.5841 0.7563 0.5631 0.6930 0.0714 0.0106 3.689 1.256 0.082S.D.b (ng m−3) 0.0125 0.0061 0.0634 0.0775 0.0330 0.1733 0.0155 0.0009 0.417 0.323 0.019R.S.D. (%) 1.9 0.9 4.0 10.3 5.9 25.0 21.8 8.5 11.3 25.7 23.4

Sample 2a

Mean (ng m−3) 0.8939 0.6128 1.0773 0.6866 0.5147 0.9398 0.1186 0.0337 3.271 1.455 0.152S.D. (ng m−3) 0.1895 0.0513 0.0777 0.0536 0.0199 0.0395 0.0107 0.0133 0.824 0.083 0.062R.S.D. (%) 21.2 8.4 7.2 7.8 3.9 4.2 9.0 39.5 25.2 5.73 40.5

Sample 3a

Mean (ng m−3) 0.0063 0.0175 0.2340 0.0581 0.3178 0.2972 0.0645 0.0355 0.316 0.615 0.100S.D. (ng m−3) 0.0009 0.0011 0.0136 0.0080 0.0178 0.0107 0.0005 0.0025 0.068 0.041 0.007R.S.D. (%) 14.2 6.4 5.8 13.8 5.6 3.6 0.8 7.1 21.6 6.7 7.1

Sample 4a

Mean (ng m−3) 0.0013 0.0040 0.0518 0.0295 0.2137 0.2394 0.0373 0.0400 0.087 0.453 0.0773S.D. (ng m−3) 0.0001 0.0009 0.0038 0.0012 0.0032 0.0298 0.0071 0.0027 0.022 0.057 0.016R.S.D. (%) 7.6 22.9 7.4 4.1 1.5 12.5 19.0 6.6 25.6 12.6 20.1

Sample 5a

Mean (ng m−3) 0.0007 0.0076 0.1117 0.0514 0.3533 0.2413 0.0773 0.0287 0.171 0.595 0.106S.D. (ng m−3) 0.0001 0.0028 0.0108 0.0011 0.0295 0.0157 0.0003 0.0006 0.070 0.063 0.002R.S.D. (%) 15.4 36.4 9.6 2.1 8.4 6.5 0.4 2.0 40.7 10.6 2.0

a n = 4.b Standard deviation.

Table 3Blanks and detection limits for individual classes of azaarenes (1�linjection)

Compound group Standard filter PUF samples

Blank (ng) Detectionlimit (ng)

Blank (ng) Detectionlimit (ng)

Two-ring azaarenes 0.3–3.7 1–13 2.1–11.4 4–22Three-ring azaarenes 0.8–1.8 1–4 3.9–7.6 7–15Four-ring azaarenes 0.13–0.15 0.3–0.4 0.03–0.23 0.1–0.5

Table 2 lists the m/z ratios monitored and the reten-tion times of the compounds in this paper. Them/z valueswere 129–171, 179–193 and 203–229 for two-, three- andfour-ring azaarenes, respectively. The response factors (rel-ative to d9-acridine) of azaarene compounds increased withincreased ring sizes. The ratios were 0.53–0.73, 0.87–0.93and 2.68–3.23 for two-, three- and four-ring compoundclasses, respectively.

3.3. Blank test and detection limit

Eight sets of blank glass fiber filters/PUF plugs wereanalyzed and the results for two-, three- and four-ringazaarenes were 0.3–3.7/2.1–11.4, 0.8–1.8/7.6–3.9, and0.13–0.15/0.03–0.23 ng in a 1�l injection, respectively.

In this study, the method detection limits (based on asignal-to-noise ratio of 3:1), are shown inTable 3for two-,three- and four-ring azaarenes were 1–13 ng (glass fiberfilter)/4–22 ng (PUF plug), 1–4/7–15, and 0.3–0.4/0.1–0.5 ng in a 1�l injection, respectively.

H.-Y. Chen, M.R. Preston / Analytica Chimica Acta 501 (2004) 71–78 77

Table 4The recoveries (%) of spiked azaarenes in different sampling materials

Compound Spiked concentration (ppm) Standard filter PUF filter PUF plug

Meana (%) S.D.b (%) Mean (%) S.D. (%) Mean (%) S.D. (%)

Quinoline 7.01 81.4 7.8 85.4 3.7 69.3 12.5Isoquinoline 9.31 88.9 14.3 80.3 5.6 79.5 9.02-Methylquinoline 7.22 90.4 2.5 91.3 7.8 89.4 13.18-Methylquinoline 6.82 75.4 10.3 87.4 6.6 75.3 9.86-Methylquinoline 7.57 82.0 8.8 84.3 9.2 82.3 6.72,6-Dimethylquinoline 7.70 80.1 4.9 82.3 11.6 77.7 12.27,8-Benzoquinoline 10.44 91.2 5.3 84.3 7.6 95.5 8.9Acridine 9.15 88.8 3.4 94.6 5.9 87.9 7.4Phenanthridine 8.99 78.9 5.1 85.3 14.2 77.5 6.49-Methylacridine 11.57 81.5 6.5 78.5 6.0 77.4 12.22-Azapyrene 2.17 65.7 18.3 62.3 16.5 54.3 5.82-Azachrysene 1.51 71.2 22.6 78.1 12.4 46.1 9.7

a The recovery test number wasn = 4.b Standard deviation.

3.4. Recovery and reproducibility

To investigate the repeatability of the whole procedurefive samples of particulate material were collected on astandard GF filter (10 in. × 8 in. ≈ 20 cm× 25 cm) by ahigh volume sampler (GMWS-2310 ACCU-VOL; GeneralMetal Works), and each sample was cut into four pieces.The samples were analyzed following the above-mentionedprocedures. The reproducibility data are listed inTable 4.Overall, the relative standard deviations (R.S.D.) var-ied within 11–40, 6–25 and 2–40% for two-, three-, andfour-ring azaarenes, respectively. Two-ring azaarenes (es-pecially quinoline and isoquinoline) have the greater co-efficients, which probably result from their relatively highvolatility. This could be the evaporation of volatile com-pounds from the particle surface during the sampling oranalysis procedures. Recovery of spiked azaarenes (Table 5)using the different types of glass fiber filters was found tobe variable but usually within 80–90, 70–90 and 60–80%for two-, three-, and four-ring species, respectively. Therecoveries of most two- and three-ring compounds werestill above 75% for azaarenes spiked into PUF plugs. How-ever, for four-ring azaarenes, the recoveries were down to46–54%.

4. Conclusions

The method described earlier was developed to collectand analyze the particulate and vapor azaarene compoundsin the ambient atmosphere. The separation method has beenshown to have potential as a practical approach to the anal-ysis for both azaarene phase. The recoveries of spiked ma-terial for most two- and three-ring compounds were >85%in different types of filter and were >75% in PUF plugs.For both four-ring species, the recoveries were between 45and 70% in different sampling materials. Application of the

method to the analysis of real sample yielded coefficients ofvariation (v) of between 1 and 36% for the different molec-ular weight of azaarene.

Acknowledgements

We would like to thank Dr. Anu Thompson for helpduring sample analysis. This work was supported by theNational Science Council of Republic of China Grant No.NSC92-2611-M-019-008.

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