19


For the analysis, the ISQ 7610 single quadrupole GC-MS, coupled with a TRACE 1610 GC gas chromatograph and equipped with the ExtractaBrite™ ion source, was used. The method conditions are shown in Table 1. The system was operated in Selected Ion Monitoring (SIM) mode to monitor the PAHs, and in full scan (from 50 to 500 m/z, dwell time 0.20 s) for the tuning solution.


Table 1. GC-MS acquisition method parameters for the determination of 19 PAHs in water and soil samples.


Injection parameters


Inlet module and mode Liner


Liner type and size


Injection volume (µL) Inlet temperature (˚C) Split fl ow (mL/min)


Carrier gas, carrier fl ow (mL/min), carrier mode


Split ratio Purge fl ow (mL/min)


Pre-injection needle wash Post-injection needle wash


Chromatographic column


Thermo Scientifi c™ TraceGOLD™ TG-PAH


Column dimensions Oven temperature program


Temperature 1 (˚C) Hold time (min)


Temperature 2 (˚C) Rate (˚C/min)


Temperature 3 (˚C) Rate (˚C/min)


Temperature 4 (˚C) Rate (˚C/min)


Hold time (min)


Total GC run time (min): MS parameters


Ion source


Transfer line temperature (˚C) Ion source temperature (˚C) Ionization type


Electron energy (eV) Emission current (µA) Acquisition mode Dwell time (s)


40 1


285 35


295 3


350 30 2


15.2 P/N 26055-0470 30 m × 0.25 mm i.d. × 0.10 µm SSL, split P/N 453A1925-UI


Thermo Scientifi c™ LinerGOLD™, 4 mm i.d. × 78.5 mm


1


300 15


He, 1.5, constant fl ow


10:1 5


5 times, with DCM


10 times with DCM, 10 times with MeOH


Naphthalene-d8 Naphthalene


2 - methyl Naphthalene 1 - methyl Naphthalene Acenaphthylene Acenaphthene


Acenaphthene-d10 Dibenzofuran


Fluorene


Phenanthrene-d10 Phenanthrene


Anthracene Fluoranthene


Terphenyl-d14 Pyrene


Benz[a]anthracene Chrysene-d12


Chrysene


Benzo[b]fl uoranthene Benzo[k]fl uoranthene Benzo[a]pyrene


Perylene-d12


Dibenzo[a,h] anthracene


Indeno[1,2,3-cd]pyrene Benzo[g,h,i]perylene


Data processing


Data were acquired, processed, and reported using Thermo Scientifi c™ Chromeleon™ 7.3 CDS software, which allows instrument control, method development, quantitative/ qualitative analysis, and customisable reporting all within one platform. The GC-MS Environmental Extension Pack includes a suite of report templates, processing methods and eWorkfl ows™ to facilitate environmental analysis by GC-MS using EPA Methods 8270, 524, 525, and 8260 [6]. For the analysis of PAHs, monitoring the ratios between the masses of the DFTPP is required and automatically performed by the software System Suitability Check. Chromeleon CDS allows rapid implementation of the PAHs method into any analytical laboratory and ensures the system produces results shortly after installation.


ExtractaBrite 350 350 EI


70 10


SIM, 2 ions/compound 0.02


A full list of analytes, as well as quantifi er and qualifi er ions that were monitored, is listed Table 2. The system was tuned with a built-in EPA Method 8270E specifi cally designed tune type.


Results and discussion Chromatographic separation and resolution of isomers


The optimised GC conditions and the high selectivity of the TraceGOLD TG-PAH capillary column allowed for chromatographic resolution of isobaric compounds in a total run time of 15.2 minutes, meeting the EPA Method 8270E requirements. Gaussian peak shapes were obtained for all the compounds, including the ones with high boiling points.


An example chromatogram obtained for a solvent standard at 0.1 ppm is shown in Figures 1 and 2. Peaks of naphthalene and benzo[g,h,i]pyrene, the fi rst and the last eluting PAHs, show gaussian and sharp peak shape from the beginning to the end of the method; baseline peak width for benzo[g,h,i]pyrene was 0.034 min.


Phenanthrene and anthracene compounds are almost baseline resolved; benzo[b] fl uoranthene and benzo[k]fl uoranthene have a resolution of 20% (calculated as the ratio between the height of the valley and the smaller height of the apex of the two compounds); dibenzo[a,h]anthracene and indeno[1,2,3-cd]pyrene coelute and rely on mass separation.


4.7 4.8 5.2 5.3 5.9 6.0 6.0 6.1 6.4 7.2 7.2 7.2 8.1 8.3 8.4 9.5 9.7 9.7


11.3 11.4 12.1 12.2 13.5


13.5 13.9


136 128 142 142 152 153 162 168 165 188 178 178 202 244 202 228 240 228 252 252 252 264 278


276 276


Table 2. List of target PAH compounds, with their retention time and SIM quantifi cation and confi rmatory ions


Compound name


Rt (min) MS quantifi er ion (m/z)


MS


confi rmatory ion (m/z)


108 129 141 141 151 154 164 139 166 184 176 176 200 122 200 226 236 226 250 250 250 260 139


138 138


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