Crude oil composition analysis up to C35

We currently use Agilent 7890A GC with S/SL injector and FID detector using a capillary column for the analysis of crude oil composition upto C35.  The remaining compounds will be reported as C36+. The temperature program is from 30 Deg to 325 Deg, We run a few blanks before injecting crude oil sample for subtracting the baseline. Because of the heavy ends in the samples, we never get consistent baseline for the blank. Is there a better configuration for this type of analysis. Currently we replace the columns very frequently.

Do we need to replace the S/SL injector with any other type?

Is it possible to have a pre-column and additional EPC to backflush the heavy ends beyond C35?

Please look into the matter and provide an alternative. 


  • There are two options I would suggest:

    1) Add a pre-column backflush heavies to vent.  You would need a purged ultimate union and additional EPC (PCM would be best).  Drawback is that you won't be able to determine how much is C36+ is in the sample.

    2) Replace the S/SL inlet with cool on-column or multimode.  For samples with wide boiling ranges, these inlets work much better in transferring sample to the column as you can ramp the inlet temperature.  I believe most (if not all) of the simulated distillation methods for samples other than gasoline recommend one of these inlets.

    Frequent column replacement is not uncommon with simulated distillation GCs, especially on the methods for heavier samples such as crude oil.  I recommend using a column designed for D2887 or high temp simulated distillation for your method.

  • Hi

    You can choose Crude Oil Analyzer which is combination of DHA and Simdis.

    Or you have to do modification as mentioned by Lance..

  • Yep - what ISH said. You've basically got a Detailed Hydrocarbon Analyser (DHA), but you likely want the front-end analysis too so you might need a DHA / Simdis merge. These are specialist applications built on Agilent hardware and AC by PAC are Agilent channel partners who specialise in this stuff. You'll get bespoke hardware and software to make naming the multitude of peaks in a crude sample more manageable (because there's a LOT). 

    But in principle, you want an inlet which is temperature programmable, like AC's TPI, and a back flush to capture the heavies and send them to vent ant not on to your analytical column.  

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