Complex polycyclic aromatic hydrocarbons from coal tar on Agilent J&W Select PAH Application Note Author Introduction John Oostdijk Coal tar is a brown or black liquid of high viscosity, which smells of naphthalene Agilent Technologies, Inc. and aromatic hydrocarbons and is obtained from the destructive distillation of coal. Formerly, coal tar was obtained as a by-product in manufacturing coal gas. It is now produced in making coke for steel making. The crude tar contains a large number of organic compounds, such as benzene, naphthalene, methylbenzene and phenols, which can be obtained by distillation. The residue is pitch. At one time coal tar was the major source of organic chemicals, most of which are now derived from petroleum and natural gas. Coal tar pitch is mainly used as a binding agent in the production of carbon electrodes, anodes and Søderberg electrodes, for example, by the aluminium industry. It is also used as a binding agent for refractories, clay pigeons, active carbon, coal briquetting, road construction and roofing. Furthermore, small quantities are used for heavy-duty corrosion protection. The standard coal tar reference material (SRM 1597a, NIST) is a natural, combustion-related mixture of polycyclic aromatic hydrocarbons (PAHs), isolated from a medium crude coke-oven tar and dissolved in toluene. However, PAHs can be difficult to analyze because some of them have the same mass. This makes their separation with GC/MS problematic, and so column selectivity and an optimized oven program are necessary to resolve these PAHs. In this application note, a coal tar sample was analyzed using an optimized oven program for the Select PAH column. As the coal tar sample is intended for use in the evaluation and validation of analytical methods for the determination of PAHs, we can clearly show the performance of the Select PAH with this reference material. Conditions space and the large number of possible Technique: GC/MS, Triple Quad configurations of the PAHs. The Column: Select PAH, 30 x 0.25 mm, relatively long run time of 45 min at the df=0.15 µm (part number CP7462) maximum programmable temperature Sample: SRM 1597a, concentration of 350 °C may affect the column approximately 0.8-21 µg/mL lifetime. (www.nist.gov) Injection Volume: 0.1 µL Temperature: 70 °C (0.70 min), 85 ºC/min, 180 °C, 3 °C/min, 230 °C (7 min), 28 °C/min, 280 °C (10 min), 14 °C/min, 350 °C (3 min) Carrier Gas: Helium, constant flow 2.0 mL/min Injector: 300 ºC, Splitless mode, 1 min @ 50 mL/min Detector: Triple Quad, EI in FS or SIM mode, ion source 275 °C, transfer line 300 °C Results and Discussion The sample was analyzed directly in full scan and SIM mode. PAHs were analyzed using the same conditions as for a standard with regulated and interfering PAHs, which made their identification possible. Chromatograms with identifications are shown in Figures 1 to 3. It can be seen from Figure 1 that chrysene (66 mg/kg) was separated from triphenylene (12 mg/kg), and benzo[b,k,j]fluoranthene (66, 37 and 41 mg/kg) from benzo[a] pyrene (94 mg/kg). The MS spectrum from chrysene is shown. As well as the molecular ion (M+) m/z 228, other ions such as m/z 226 and m/z 229 were formed. The PAHs were mostly very stable and only low fragment ions were observed, such as m/z 113 and 114 in this mass spectrum. In addition, a group-type analysis of high molecular weight PAHs was possible, which is shown in Figure 4. PAHs with higher molecular weight (MW>302) were eluted at 350 °C due to the maximum programmable column temperature. Many isomers of high molecular weight were in the coal tar sample. Complete separation, however, was not possible on a single column because of the limited separation 2 Table 1. Peak Indication for Figure 1 BaA Benzo[a]anthracene BaP Benzo[a]pyrene BpFA Benzo[b]fluoranthene BkFA Benzo[k]fluoranthene BjFA Benzo[j]fluoranthene CHR Chrysene CPP Cyclopenta[c,d]pyrene TP Triphenylene MS spectrum of Chrysene 228 800000000.00 700000000.00 226 BbFA 114 BaP 600000000.00 100 120 140 160 180 200 220 240 m/z BaA BkFA 500000000.00 BjFA CHR 400000000.00 CPPTP m/z 228 m/z 252 403500000.00 m/z 226 353500000.00 300000000.00 303500000.00 253500000.00 203500000.00 153500000.00 103500000.00 200000000.00 53500000.00 23 24 25 26 27 28 29 30 31 32 33 100000000.00 0.00 0 5 10 15 20 25 30 35 40 Time [min] 45 Figure 1. GC/MS analysis of SRM 1597a (0.1 µL) in full scan mode on Select PAH 3 Table 2. Peak Indication for Figure 2 ACL Acenaphthylene (263 mg/kg) BghiP Benzo[g,h,i]perylene (51 mg/kg) NA Naphthalene (1030 mg/kg) BaA Benzo[a]anthracene (98 mg/kg) DBaeP Dibenzo[a,e]pyrene (9 mg/kg) PHE Phenanthrene (454 mg/kg) BaP Benzo[a]pyrene (94 mg/kg) FA Fluoranthene (327 mg/kg) PY Pyrene (240 mg/kg) 350 NA 90000000.00 °C TIC SIM 300 TIC SIM 50x zoomed 70000000.00e 250 BaA 50000000.00MS respons BaP 200 PHE ACL BghiP 30000000.00 150 DBaeP FA 10000000.00 PY 100 -10000000.00 50 0 5 10 15 20 25 30 35 40 45 Time [min] Figure 2. GC/MS analysis of SRM 1597a (0.1 µL) in SIM mode on Select PAH. The final part of the chromatogram is enlarged because of the large concentration difference in the sample Table 3. Peak Identification for Figure 3 ATR Anthanthrene (Dibenzo[def,mno] BbPer Benzo[b]perylene DBaeP Dibenzo[a,e]pyrene chrysene) BbTP Benzo[b]triphenylene DBahP Dibenzo[a,h]pyrene BaFA Benzo[a]fluoranthene BcFL 7H-benzo[c]fluorene DbaiP Dibenzo[a,i]pyrene BaFL Benzo(a)fluorene BeP Benzo[e]pyrene DBalP Dibenzo[a,l]pyrene BaP Benzo[a]pyrene BghiP Benzo[g,h,i]perylene IP Indeno[1,2,3-c,d]pyrene BbCHR Benzo[b]chrysene BjFA Benzo[j]fluoranthene 6MC 6-Methylchrysene BbFA Benzo[b]fluoranthene BkFA Benzo[k]fluoranthene 5MC 5-Methylchrysene BbFL Benzo(b)fluorene Cor Coronene Per Perylene BbNTP Benzo(b)naphto(2,1-d)thiophene DBahA Dibenzo[a,h]anthracene Pic Picene 4 A B A m/z 216 B m/z 242 BaFL BbFL BcFL 5MC 6MC 15C 15.5 16 16.5 17 17.5 18 18.5 19 19.5 20 26 26.5 27 27.5 28 D BaP m/z 278 C m/z 252 D BghiP m/z 276 BbFA IP BkFA BjFA BeP ATR BaFA Per DBahA BbCHR Pic BbTP 29.7 30.2 30.7 31.2 31.7 32.2 32.7 F 38.2 38.7 39.2 39.7 40.2 40.7 E E m/z 300 F m/z 234 m/z 302 BbNTP DBaeP DBalP+coelution BbPer Cor DBaiP DBahP 42.3 42.8 43.3 43.8 44.3 44.8 20 21 22 23 24 25 26 Figure 3. GC/MS analysis of SRM 1597a (0.1 µL) in SIM mode on Select PAH. Some examples of critical separations are shown: A. Benzofluorenes, B. Methylchrysenes, C. Benzofluoranthenes and isomers, D. Dibenzoanthracenes and isomers, E. Dibenzopyrenes and isomers, .F Benzo[b]naphtho[ ] thiophene isomers 5 TIC SIM m/z 302 (zoomed 5x) m/z 326 (zoomed 20x) m/z 350 (zoomed 100x) m/z 374 (zoomed 500x) 90000000 70000000 e Figure 2B MS respons m/z 374, eg C30H14 50000000 m/z 350, eg C28H14 30000000 m/z 326, eg C26H14 m/z 302, eg C H 10000000 24 14 -10000000 0 10 20 30 40 50 60 70 80 90 Time [min] Figure 4. GC/MS analysis of SRM 1597a (1 µL) in SIM mode on Select PAH Conclusion The Select PAH column separated target PAHs in a complex mixture of coal tar in a single run with a runtime of 45 min. For eluting higher MW PAHs, a longer run time is necessary. 6 References Sander LC and Wise SA, (1997) Polycyclic Aromatic Hydrocarbon Beekman M., Boersma, A.H.R. and. Structure Index, NIST Special Sijm, D.T.H.M. 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