The analysis of organic matter in coke oven emissions

The analysis of organic oven emissions Peter

J. Kirton,

John

Ellis

and

Phillip

matter

in coke

T. Crisp*

Department of Chemistry, University of Wollongong, PO Box 1144, Wollongong, NS W 2500, Australia *School of Chemical Engineering andlndustrial Chemistry, University of New South Wales, PO Box 7, Kensington, NSW 2033, Australia (Received 22 November 7990)

A detailed analysis of coke oven emissions is reported. Measurements were made on samples collected at various workplace locations on the oven top. A new type of sampling system was used and is described. Results range from volatile monoaromatic compounds including benzene to polycyclic aromatic hydrocarbons (PAH) of six fused rings. Estimates of errors which may arise when sampling for PAH by filtration are given (Keywords: analysis; organic matter; emissions)

The polycyclic aromatic hydrocarbon (PAH) class of compounds is becoming recognized as a ubiquitous contaminant in the atmosphere. The concentration of PAH in air is normally low, but at some industrial sites, where they are generated by various processes, PAH may be present in amounts which pose health problems. The coke making, aluminium smelting and petroleum refining industries are actively involved in monitoring levels of PAH for assessment of worker exposure. There is a growing awareness among occupational hygienists that many non-PAH compounds are present in industrial emissions, and a knowledge of the composition of emissions is necessary for a true appreciation of the value of empirical worker exposure tests. An assessment of the overall profile of organic compounds needs to be performed separately for each industry. In this work, we report on an analysis of organic compounds in coke oven emissions, aiming to characterize the emissions both for vapours and for particulate PAH. Gases evolved during carbonization of coal in coke ovens may leak from the oven during the operations of coal charging and coke pushing, and at other times due to poor sealing. Several authors have reported the analysis of PAH compounds in coke oven emissions’-3, and the analyses show the presence of compounds which are either known or suspected carcinogens. These analyses do not, however, fully characterize coke oven emissions because of deficiencies in sampling which have been discussed previous1y4. Collection of samples on a filter alone results in evaporative loss of volatile compounds, including many PAH, and in the few studies which have used some form of back-up to trap volatile compounds, only a small number of major components have been reported3.‘s6. A thorough characterization of coke oven emissions should allow a better assessment of exposure of workers than is possible with the empirical tests currently 0016~2361:‘91;121383-07 (” 1991 Butterworth-Heinemann

Ltd

performed. This in turn should lead to a better understanding of the occupational health significance of coke oven emissions, and enable a sound choice of marker compounds for biological monitoring of exposure.

EXPERIMENTAL Reference compounds used for calibration were of 398% purity. Filters were cut from 37 mm Teflon filter membranes of 2 pm pore size. Graphitized carbon and coconut charcoal were used as adsorbents, and carbon disulphide (CS,) used as desorbing solvent. Chromatoyraphy

All determinations were performed by gas chromatography using a flame ionization detector (g.c.-f.i.d.), with a BP-5 capillary column. The capillary system was operated in the split mode, using a split ratio of 1O:l. High purity hydrogen was used as carrier gas at a flow rate of 8.5 cm s-l. A 1 ,~l injection was made at a column temperature of 3O”C, which was held for 2 min. The column was heated at a rate of 4°C min ’ to 300°C. A mixture of 48 aromatic compounds in benzene (Table I) was used to derive calibration factors. Where standards were not available, factors were determined by interpolation. Three internal standards, hexadecane, eicosane and triacontane, were added to each sample for quantitation. Muss spectrometry

The g.c.-m.s. of coal tar was performed with the aid of a computer-based library system. Spectra1 searches were performed using both the NIST library and the 1988 Registry of Mass Spectral Data’.

FUEL, 1991, Vol 70, December

1383

Analysis Table 1

of organic Standard

mixture

matter:

P. J. Kirton

of aromatic

compounds

et al. for calibration Concentration (Icg ml-‘)

No

Compound

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 41 48

Ethylbenzene p-Xylene m-Xylene o-Xylene Styrene 1,3,5_Trimethylbenzene 1,2,4-Trimethylbenzene t-Butylbenzene p-Isopropyltoluene n-Propylbenzene Isopropylbenzene Diethylbenzene (mixture) m-Ethyltoluene Indan Indene I ,2,3,5_Tetramethylbenzene

1,2,4,5_Tetramethylbenzene Tetralin Naphthalene 2-Methylnaphthalene I-Methylnaphthalene Dimethylnaphthalenes Biphenyl Acenaphthene Acenaphthylene Dibenzofuran Fluorene Acridine Phenanthrene Anthracene Carbazole Fluoranthene Pyrene Benzo[u]fluorene Benzo[b]fluorene Benz[a]anthracene Chrysene Naphthacene Benzo[h]fluoranthene Benzo[j]fluoranthene Benzo[k]fluoranthene Benzo[r]pyrene Benzo[a]pyrene Perylene Indeno( I ,2,3-cd)pyrene Dibenz[a,h]anthracene Benzo(ghi]perylene Coronene

260 344 346 352 362 175 143 87 86 86 172 173 138 193 966 445 665 485

1000 (mixture

915 494 502 940 100 X36 452 800 116

1000 446 456 909 970 150 40 400 376 52 34 186 65 653 550 91 42 149 x9 66

treatment

Filters were extracted ultrasonically for 30 min with 400 ~1 of CS, in a 1 ml vial. The CS, was also used for extraction of the adsorbents-700 ~1 for graphitized carbon and 400 ~1 for charcoal. Ultrasonication was not necessary for the adsorbents. Each extract (100 ~1) was withdrawn by syringe and transferred to another 1 ml vial, to which was added 50 ~1 of internal standard solution. With the exception of the filter extract, analysis was performed on this solution. The filter extract was concentrated to 20 ~1 by gentle evaporation under a stream of dry nitrogen, this having been shown to cause no evaporative loss of the compounds in this fraction. A 1 ~1 sample was used for chromatography. RESULTS

AND

DISCUSSION

Coke Oven tar

Crude coke oven tar is formed when the gases produced during carbonization of coal are condensed by an aqueous liquor spray. Crude tar provides an ideal source material for qualitative assessment of the compounds which may be found in coke oven emissions. The composition of coal tar has been well characterized’-ll. It can be broadly classified into two portions, one of high molecular weight (asphaltenes, resins) and one of lower molecular weight. The latter portion consists of aliphatic and aromatic hydrocarbons, sulphur, oxygen and nitrogen heterocyclic compounds, phenolic compounds and other classes in trace amounts”. The aromatic hydrocarbons, especially PAH, are by far the most abundant compounds in coke oven tar, and have thus received most attention in analysis of coke oven emissions. Two samples of crude tar were obtained from the coke ovens at BHP, Port Kembla, NSW. Coke at Port Kembla is produced from coal mined on the south coast of New South Wales and is a blend of premium grade coking coals with an IS0 classification of 434-435. The composition of the tar samples was determined by g.c.-f.i.d. and g.c.-m.s. analysis. Mass spectrometry alone is not a definitive tool for PAH identification. The molecular ion is, in general, the base peak. Other ions are M-l and M-2 (intensity, M-l < M-2), M-CHX (where X is CH, N, NH, 0 or S) Table 2 Abundance of PAH (relative to MW 228)

Sampliny

A sampling train consisting of a 13 mm filter and the two adsorbents in series (300 mg graphitized carbon and 150 mg charcoal) was used for collection of fume samples. Previous experiments’ have shown that hydrocarbons of six or more carbons are completely trapped by this system. The samplers were placed statically at locations 1 m above the battery top. Samples were taken at various locations on the battery top, both near to and remote from ovens being charged and pushed, but never directly in obvious emission sources. Air was sampled for 6 h at 1 1 min- ’ using a personal sampling pump. The sampling time was usually 6 h and the average temperature during sampling was 35°C with a maximum of 43’C. The positioning of samplers, and the sampling time, allowed an averaging effect of coke oven operation cycles, so that air being sampled was representative of the general workplace.

1384

Sample

FUEL,

1991,

Vol 70, December

by direct

Molecular weight

Abundance relative MW 228 (by direct insertion m.s.) coal tar

178 202 22x 252 276 27x 302 326 350 376 400 424 450

3.97 3.50 1.OO 1.37 0.45 0.20 0.32 0.2 1 0.09 0.06 0.015 0.006 0.002

insertion

m.s. and g.c.-f.i.d.

to Abundance relative MW228 (by g.c.-f.i.d.) coal tar 3.82 3.50

1.oo 1.21 0.51 0.16 0.38 _ _

to

Analysis Table 3

No.

Composition

of coke oven emissions

I

Alkanes Benzene

matter: P. J. Kirton et al.

of six or more carbons Retention index

Compound

2

for compounds

of organic

Molecular weight _

> C6

78

Mean (X)

Max. (%)

Min. (%)

1.74

3.42

0.59

33.53

47.48

24.5 I

3

Toluene

92

8.85

10.83

6.66

4

Ethylbenzene

106

0.52

0.94

0.33

5

p-Xylene,

106

4.69

7.46

2.79

6

Styrene

104

0.87

1.71

0.09

7

o-Xylene

106

1.09

2.07

0.57

8

n-Propylbenzene

120

0.42

0.55

0.22 0.22

m-Xylene

120

0.49

0.65

10

Cyanobenzene

165.12

103

0.31

0.36

0.25

11

Pseudocumene

166.05

120

0.56

0.84

0.3 I

12

Phenol

166.59

94

1.72

2.96

0.38

13

Benzofuran

168.01

118

0.29

0.48

0.04

14

Indan

172.96

118

0.15

0.25

0.04

15

Indene

174.42

116

2.79

3.69

0.9 I

16

Cresols

108

0.48

0.9x

0.07

17

Xylenols

122

0.20

0.34

0.04

IS

Methylindenes

130

0.17

0.25

0.04

19

Naphthalene

200.00

128

17.11

26.6 I

8.18

20

Benzo[h]thiophene

201.35

134

0.23

0.30

0.07

21

Other

0.66

1.12

0.27

22

2-Methylnaphthalene

220. I4

142

I .66

2.26

0.66

23

I-Methylnaphthalene

223.04

142

0.74

0.95

0.24

24

Methylbenzothiophenes

148

0.10

0.17

0.03

25

Indole

221.71

117

0.04

0.07

0.02

26

Quinoline

211.10

129

0.05

0.07

0.04

27

Biphenyl

235.92

154

0.37

0.52

0. I7

28

Dimethylnaphthalenes

156

1.38

1.86

0.92

29

Acenaphthylene

247.53

152

1.40

2.30

0.5 1

30

Acenaphthene

253.24

154

0.29

0.52

0.1 I

31

Methylbiphenyls

170

0.30

0.50

0.1 1

32

Dibenzofuran

168

1.30

2.02

0.64

33

Trimethylnaphthalenes

170

0.24

0.56

0.07

9

Mesitylene

alkylated

benzenes

258.73

34

Fluorene

166

0.96

I .98

0.44

35

Methylacenaphthylenes

166

0.29

0.45

0.04

36

Methyldibenzofurans

1x2

0.12

0.13

0.1 I

180

0.69

1.29

0.20

0.50

0.27 0.1 1

37

269.62

Methylfluorenes

38

Dimethyldibenzofurans

196

0.38

39

Dibenzothiophene

295.63

I84

0.20

0.36

Phenanthrene

300.00

178

3.34

5.43

1.65

41

Anthracene

301.34

178

0.84

1.42

0.50

42

Acridine

303.75

179

0.07

0.12

0.01

43

Phenanthridine

307.63

179

0.11

0.36

0.01

44

DimethylBuorenes/trimethyldibenzofurans

194!210

0.03

0.04

0.02

45

Carbazole

167

0.14

0.36

0.03

46

Methylphenanthrenes,imethylanthracenes

192

0.56

0.72

0.10

47

4H-cyclopenta[def]phenanthrene

190

0.14

0.26

0.03

48

Methylcarbazoles

181

0.03

0.07

0.01

49

2-Phenylnaphthalene

204

0.07

0.2 1

0.00

50

Methylbenzoquinolines

193

0.12

0.19

0.04

51

Dimethylphenanthrenes/anthracenes

206

0.11

0.25

0.04 0.90

40

310.79 32 1.96

331.63

52

Fluoranthene

344.50

202

1.53

2.84

53

Acephenanthrylene

347.82

202

0.06

0.07

0.01

54

Phenanthro[4,5-hcdlthiophene

349.16

208

0.07

0.11

0.05

55

Aceanthrylene

350.31

202

0.05

0.10

0.01

56

Pyrene

351.85

202

1.05

I .95

0.61

FUEL,

1991,

Vol 70, December

1385

Analysis Table 3

of organic

matter:

P. J. Kirton

et al

continued

No.

Compound

Retention index

Molecular weight

51

Methylphenylnaphthalene

353.49

218

0.02

0.03

0.01

58

Benzonaphthofurans

218

0.06

0.13

0.02

59

Azafluoranthene/azapyrene

203

0.01

0.01

0.01

60

4H-benzo[d
363.75

191

0.07

0.20

0.01

61

Benzo[a]fluorene

366.49

216

0.09

0.24

0.03

62

Benzo[h]fluorene

368.99

216

0.06

0.13

0.02

63

Methylfluoranthenes

216

0.03

0.10

0.01

64

Methylpyrenes

216

0.03

0.09

0.01

Mean (%)

Max. (%)

Min. (%)

______

65

Methylbenzfluorenes/dimethylfluoranthenes~pyrcnes

230

0.10

0.53

0.01

66

Benzo[h]naphtho[Z,l-dlthiophene

389.15

234

0.14

0.31

0.07

67

Benzo[ghi]fluoranthene

390.25

226

0.06

0.13

0.03

68

Benzo[c]phenanthrene

390.96

228

0.05

0.11

0.02

69

Benz[c]acridine

392.40

229

0.08

0.15

0.03

70

Benzo[h]naphtho[l,2-dlthiophene

391.83

234

0.06

0.11

0.02

71

Benzo[h]naphtho[2,3-dlthiophene

395.57

234

0.06

0.21

0.02

72

Cyclopenta[cd]pyrene

397.20

226

0.03

0.07

0.01

73

Benz[u]anthracene

398.62

228

0.47

1.Ol

0.27

14

Chrysene

400.00

228

0.50

I .05

0.29

75

Benzocarbazoles

217

0.16

0.67

0.04

+ triphenylene

76

Naphthoquinolines

229

0.13

0.16

0.10

17

Naphthacene

403.59

228

0.09

0.13

0.05

78

Benzanthrone

410.38

230

0.10

0.13

0.07

79

Methylchrysenes/benz[a]anthracenes

242

0.14

0.71

0.02

80

4H-cyclopenta[def$hrysene

240

0.11

0.47

0.03

81

Binaphthyls

254

0.12

0.17

0.06

82

Benzo[b]fluoranthene

252

0.42

0.85

0.25

83

B[ j]F + B[k]F

84

Benzo[a]fluoranthene

isomers

442.45

252

0.30

0.52

0.15

252

0.08

0.14

0.04

85

Methylbinaphthyls

446.21 _

268

0.09

0.13

0.04

86

Benzo[e]pyrene

452.03

252

0.32

0.57

0.2 I

87

Benzo[a]pyrene

453.76

252

0.34

0.56

0.18

88

Perylene

252

0.09

0.20

0.04

89

Methylbenzfluoranthenes/methylbenzpyrenes

456.90 _

266

0.53

0.61

0.39

90

Indeno[7,1,2,3-cdeflchrysene

489.82

276

0.04

0.13

0.02

91

Dibenz[uj]anthracene

490.58

278

0.04

0.08

0.02

92

Indeno[1,2,3-cdlpyrene

492.12

276

0.16

0.25

0.10

93

Dibenz[a,h]anthracene

494.53

278

0.04

0.07

0.03

94

Benzo[b]chrysene

497.49

278

0.02

0.04

0.01

95

Picene

498.72

278

0.02

0.05

0.01

96

Benzo[ghi]perylene

500.00

276

0.15

0.25

0.09

97

Anthanthrene

503.94

276

0.06

0.32

0.02

98

Coronene

300

0.02

0.03

0.01

99

Total

545.41 _

302

0.23

0.36

0.12

MW 302

charged M/2e and (M-CHX)/2e. and the doubly Methyl-substituted PAH and ring systems contaming a benzylic carbon (e.g. fluorene, 4H-cyclopenta[def]phenanthrene) exhibit an M-l ion of greater intensity than M-2 and this can be diagnostic of these compounds. The nitrogen-containing PAH are readily identifiable by odd-numbered molecular weights and sulphur-containing PAH exhibit M-32 and M-33 ions. This pattern is common to isomers and differentiation between isomers is not possible by m.s. Identifications were assigned to 183 peaks on the chromatogram of coal tar by correlation of g.c.-m.s.

1386

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1991,

Vol 70, December

results, published data1°-12 and the use of pure standards. In every case, PAH and structurally related heterocyclic PAH exhibited the same retention order (0-PAH, C-PAH, S-PAH, N-PAH). This observation aided in peak identification. Retention indices (RI), based were calculated for both hydrogen on the Lee systemI and helium carrier gas and compared with literature values’ 1,13-15. Retention indices are calculated from a comparison of retention time of each component with the retention time of four reference compounds (naphthalene, phenanthrene, chrysene and picene)13. In practice, picene is only a minor constituent of coke oven

Analysis

of organic matter: P. J. Kirton et al.

c

FUEL,

1991,

Vol 70, December

I

1387

Analysis

of organic

matter:

P. J. Kirton

et al

tar and emissions and its retention time cannot always be determined with confidence. A major component, benzo[ghi]perylene, was used instead as the fourth reference compound for calculation of RI. The g.c. is limited to volatile compounds. The use of thin film capillary columns extends its application to compounds of low volatility, but, for PAH analysis, the technique is usually limited to PAH of molecular weight (MW) up to 302 (dibenzopyrenes and naphthofluoranthenes). Direct insertion m.s. of coal tar was used to verify the distribution of PAH as found by g.c., and to indicate the relative abundance of compounds above MW 302. Tuble 2 shows the abundance, in tar, of the molecular ion for PAH of MWs up to 450 relative to benz[a]anthracene and chrysene (MW 228) as found by direct insertion m.s., and the g.c. response for classes up to MW 302. Table 2 is useful in predicting the mass, in an air sample, of those compounds which cannot be determined by g.c.

Coke ot’en emissions

Thirteen emission samples were collected to provide the data for this work. During the sampling period, the battery was being charged and pushed at five-oven intervals. This created a mixture of ovens in various stages of the coking cycle over a space of a few metres each side of the sample location. Turbulence, caused by thermal updraughts and ambient breezes, further assisted mixing of emissions above the ovens. The 13 samples were collected at various locations on the battery top. This mixing and varying of sample point acted to minimize any bias in the analytical results. All sample extracts were analysed by g.c.-f.i.d.. Selected filter and adsorbent extracts were also analysed qualitatively by g.c.-m.s.. Identifications were assigned to over 230 peaks on the chromatograms of the three sample fractions (filter plus two adsorbents) based on RI, mass spectral data and injection of known standards. This list was condensed to 99 peaks (Table 3) by grouping methyl-, dimethyland trimethyl-PAH and some isomeric PAH for which reference compounds were not available. G.c.-m.s. analysis did not extend to the 302 MW PAH. Coronene (MW300)co-elutes with this group on a BP-5 column and was used to provide a response factor for measurement. Individual peaks were tentatively identified by compar\ison with published data” but in the absence of suitable reference compounds, their masses were grouped for this work. Typical chromatograms from each sampler section are shown in Figure 1, and a summary of the analysis of the 13 samples is given in

25-35 ppb NO,. These concentrations may be higher in the immediate vicinity of the coke ovens. The absolute mass of individual compounds varied from sample to sample, but the percentage contribution of each to the total was relatively constant (Table 3). The maximum range of variation in total emissions was variation in the 150-1600 pg mm3, and the limited relative proportions of the many components confirms the adequacy of the sampling system (location, sampling time and sampling device). The sampling device had previously been used with a synthetic standard mixture only, and this work shows that it was effective in generating a sample of sufficient concentration for analysis by high efficiency capillary g.c. A complete analysis of coke oven emissions is too complex for routine application, and occupational hygienists prefer to have an index figure for recording occupational exposure. From the approximately consistent relative proportions of the components in emissions, it seems that the overall composition of emissions from coke ovens can be inferred from the analysis of a relatively few major compounds (e.g. the 16 Environmental Protection Agency (EPA) PAH and benzene). Obviously, a full analysis of workplace air must be made before this generalization can be applied to other industrial sites.

CONCLUSIONS Many of our findings are significant for health studies at coke ovens. The US EPA has declared 16 priority pollutant PAH’I. The concentrations found for these 16 compounds (Figure 2) are frequently used to gauge the overall levels of PAH in air samples. Depending on the sampling protocol selected, these compounds are trapped on a filter alone or filter + Tenax GC or filter + XAD-2. Our work has shown that: 1. filter alone (OSHA) is completely inadequate for trapping PAH (half of the 16 EPA PAH are completely

Table 3.

There is some concern that the action of airborne oxidants such as NO, and 0, on sampled PAH produces sampling artefacts, causing errors in analysis’ 7- I’. This study found no gross artefact formation in emission samples. The limit of component detection for filter samples (after concentration) was 0.01 pg. This equates to 0.03-0.05 pg mm3. The detection limit for adsorbent extracts was 0.05 pg or 0.15-0.20 /lg rne3. A minor trace of benzanthrone (identified by m.s.) was the only quinonc (caused by photo-oxidation or 0,) found above this level. No nitro-PAH (formed by reaction of PAH with NO,) was found. Ambient levels of these oxidants’” in the Port Kembla area are approximately 30 ppb 0, and

1388

FUEL,

1991,

Vol 70, December

Figure 2

adsorbents

Distribution

(q )

of

16 EPA

PAH

between

filter

(m)

and

Analysis

retained

and the other half are scarcely retained at all to coke oven emissions is mostly monitored by the OSHA technique22 which is based on the mass of organic material trapped on and subsequently extracted from a filter. In this study, the filter retained only 5% by mass of all organic material sampled, 25% of PAH of three or more rings and < 10% of the EPA priority PAH; 2. filter + Tenax (EPA) gives incomplete retention of naphthalene8; 3. filter + XAD-2 (EPA, NIOSH23) is the only standard procedure capable of retaining the entire 16 PAH compounds’. The efficiency of XAD-2 drops at elevated sampling temperature. (Figure 2). Exposure

Our work demonstrates that graphitized carbon quantitatively retains all PAH compounds, even at sampling temperatures as high as 43’C. The above standard methods all have a serious deficiency: they do not trap very volatile compounds, especially benzene, a known carcinogen. The monoaromatics are major constituents of coke oven emissions (T&e 3) and are trapped quantitatively by our procedure. An average concentration for benzene of 0.3 mg mm 3 was found, and this is significant if proposals to lower the exposure standard or threshold limit value for benzene to 0.1 ppm (0.3 mg mp3) take effect24. The use of a three-stage sampler allows determination of a wide range of the constituents of coke oven emissions. It also offers the choice of gravimetric determination by filter of organics in air if a result equivalent to the OSHA standard test is desired. Work is proceeding to apply this sampling device for worker exposure monitoring at coke ovens and then for general workplace sampling.

I 2 3 4 5 6 7 8 9 10 11 I2 13 14 15 I6 17 IX 19

20 21

23

The authors thank BHP support of this research.

24

Limited

for their

continuing

matter: P. J. Kirton et al.

REFERENCES

22

ACKNOWLEDGEMENT

of organic

Lao. R. C.. Thomas, R. S. and Monkman. J. L. /. Cltronrrrloqr. 1975. 112, 681 Bjorseth, A., Bjorseth, 0. and Fjeldstad, P. E. Scar&. J. II%. EmGwtz. H/I/I. 1978, 4, 224 Andersson, K.. Levin. J.-O. and Nilsson, C.-A. C/renro.\/&rr~ 1983, 12, 197 Kirton. P. J. and Crisp, P. T. Fur/ 1990, 69. 633 O&on, R.. Leach, J. M. and Chung. L. T. K. Amd. C%enr. 1987. 59, 1701 Josis. C. Report no. ENVX CJ;56, Environmental Control Department, CRM. Belgium, 1989 ‘The 1988 Registry of Mass Spectra1 Data (CD-ROM Edition)‘, Wiley Electronic Publishing, New York, 1988 Kirton, P. J., Ellis, J. and Crisp. P. T. Fw/ 1991, 70. 4 Borwitzky, H. and Schomburg, G. J. Chronurmy~. 1979. 170.99 Novotny,M..Strand,J. W.,Smith,S.L.rtrr/. Fu~~/l981.60,213 Wise, S. A., Benner, B. A., Byrd, G. D. et (I/. A&. c’hcn~. 1988. 60, 887 Wise, S. A.. Benner. B. A., Chesler, S. N. et rrl. Ad. Chew. 1986,X 3067 Lee. M. L., Vassilaros, D. L., White. C. M. et cr/. And. Chrm. 1979, 51. 766 Vassilaros, D. L., Kong, R. C.. Later, D. W. CI cr/. J. C/IWIP~N~O(II.. 1982, 252, I Rostad, C. E. and Pereira. W. E. J. High Rcwdut. Chron~crto~qr. Chronm~gr. Comn~un. 1986, 9. 328 Wise, S. A., Benner, B. A., Liu, H. CI u/. A&. Chem. 1988. 60, 630 Brorstrom-Lunden, E. and Lindskog, A. E/tri,on. Sci. T&no/. 1985. 19.313 Peters, J. and Seifert, B. A/mo~. Enriro~~. 1980, 14, I I7 Lee. M. L.. Novotny. M. V. and Bartle, K. D. in ‘Analytical Chemistry of Polycyclic Aromatic Compounds’. Academic Press, New York, 1981 SPCC in ‘Air Quality Measurements in New South Wales’. NSW State Pollution Control Commission Annual Review, 1987 US EPA in ‘Compendium of Methods for the Determmation of Toxic Organic Compounds in Ambient Air. US EPA Document no. 600!4-84-041’. Environmental Monitoring Systems Laboratory. US EPA, Research Triangle Park, NC. 1984 OSHA in ‘Occupational Safety and Health Administration. OSHA Methods Manual’, Organic Methods Evaluation Branch. OSHA Analytical Laboratory, Salt Lake City, Utah, 1986 NIOSH in ‘Manual of Analytical Methods. 3rd Edn’. National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication no. (84-100). Cincinnati. OH. 1982 ACGIH in ‘Annual Report of the Committees on Threshold Limit Values and Biological Exposure Indices, 16 May 1990’. American Conference of Governmental Industrial Hygienists. Orlando. 1990

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1991,

Vol 70, December

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