Determination of phenol in dicumyl peroxide

[rosemary]

Hello, I'm an italian girl and I'm doing a stage for my degree.
I'm searching a method to determine phenol, cumene, a-metilstyrene, acetophenone, 2-phenyl-2-propanol and cumene hydroperoxide content in dicumyl peroxide by capillary gaschromatography, using external standard method.
Working conditions are:
-column lenght: 6 metres
-carrier gas: He
-detector: FID
-manual injection with on column injector
-T on column injector: 40°C
-T column: 40°C for 4min
40°C-80°C at 12°C/min
80°C-130°C at 20°C/min
130°C-200°C at 3°C/min
isothermal at 200°C 3 min
-T FID detector: 230°C
-sample size: 1 microliter.
The solvent I used to pepare my standards was n-hexane. I obtained good results, except for phenol. In this case results were icoherent because for a lower concentration I obtained a bigger area.
I supposed phenol didn't dissolve completely in exane and I used MeOH as solvent but I didn't obtain better results.
What could is it due to? Could yuo suggest me somethig?
Thank you very much! (and sorry for my english, I hope you understand )

[chromatographer1]

have you repeated your results?

Have you tried to use a chlorinated solvent like methylene chloride?

You may have enough actives sites on your column that if the higher concentration std was injected first you may have lost phenol and essentially deactivated your column for the second std. Or conversely, you may have absorbed phenol initially and rinsed it off the column with the second injection of your lower concentration std.

Could the phenol have reacted with the Cumyl peroxide?

Could the peroxide reacted with active sites on the column and 'deactivated' it, reducing the absorption of the phenol for the second std?

Lots of possibilities here. Interesting analytical test.

best wishes,

Rod

[rosemary]

Thanks a lot for your suggestions!
I suspect column I use for this type of analysis is inadequate because too old and it's time to replace it.
Do you think the problem I have with phenol determination could depend on the state of the column I use?
Thank you very much

[chromatographer1]

Since you are doing on-column, even the condition of your 'needle', may affect the outcome.

Most certainly the condition of your column will affect the measurement of any reactive components of your analysis.

[rosemary]

Sorry my ignorance, but why you say that with an on column injector even the condition of my needle may affect the outcome?

[chromatographer1]

Hopefully, not, but it can. Anything with which your sample comes into contact can affect how much gets onto the column.

The condition of the column affects how much of your sample after it is injected gets to the detector.

The condition of your detector affects the amount signal produced by the sample reaching it.

These are all factors any chromatographer must consider when
trouble-shooting an analytical inconsistency.

That is why it is wise to duplicate a problem and then change factors one at a time until the problem is identified and hopefully corrected.