Tailing problem during PAH's analysis. GC/MS 7820A/5977E

Hello everyone,

Our system is 7820A/5977E we have a tailing problem during PAH's analysis.

The method we used is:

Injection Volume: 1 µl

55 C held for 5 min, 25 C/min to 320 C, held for 3 min

Carrier gas: He 1.5 ml/min

Column: HP 5: 30m x 0,25 mm x 0,25 µm

Liner: 4mm id, dual taper deactivated, no wool

Mode: P.Splitless

Acquisition mode: EI, SIM (1 to 200 pg)

Aux: 290 C, Ions Source:340 C, MS Quad: 150 C

What we made until now is:

Cleaning the Inlet and the ion source, using different Liners. increase Transfer line temperature to 340 C. Change the column, new pre, and post-column, Septa and O-Ring, different solvents, bake out the MSD, and different PAHs standards.


Air/Water check:

18/69 = 0.59 Water% (counts=5538)

28/69 = 2.36 Nitrogen% (counts=22200)

32/69 = 1.29 Oxygen% (counts=12140)

44/69 = 0.17 Carbon Dioxide% (counts=1586)



Any comments and suggestions will be appreciated

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