Fast Analysis of PAHs using Split Injection and a Short GC Column

Click on the this link:  Fast Analysis of PAHs  to see how I analyzed the EPA 16 polycyclic aromatic hydrocarbons (PAHs) in under 10 min using GC-MS by employing split injection with a Restek Premium Precision split liner with wool and a 15m x 0.25mm x 0.25µm Rxi-5Sil MS GC column.  Split injection allows a higher GC oven temperature start with good focusing for naphthalene, the most volatile PAH.  And the Rxi-5Sil MS stationary phase (5% phenyl type) is silphenylene, a backbone modification that provides a faster separation for benzo[b]fluoranthene and benzo[k]fluoranthene versus a typical 5% diphenyl column like the Rxi-5ms.

In addition to the speedy separation of the benzofluoranthenes, note the almost baseline separation for indeno[1,2,3-cd]pyrene and dibenz[a,h]anthracene.  Not bad!

Although you’ll see literature that encourages faster GC analyses through employment of smaller inside diameter columns, I prefer the 15m x 0.25mm x 0.25µm due to the better sample loading capacity for the 0.25mm x 0.25µm over something like 0.18mm x 0.18µm or 0.15mm x 0.15µm columns.  In addition, the larger ID column has better ruggedness than the smaller bore columns.

One more note on the use of 15m x 0.25mm x 0.25µm versus 30m x 0.25mm x 0.25µm columns.  Under vacuum-outlet conditions, i.e., using MS, the analysis time is about 3 times shorter for the 15m column.  You can prove that to yourself with the EZGC Method Translator and Flow Calculator.

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