Detector sulfur (SCD355)

[Ana Paula]

Have a gas chromatograph coupled to the detector nitrogen and sulfur (SCD355) and when using Agilent oven to 360 ° C, the ceramic tube of the SCD (sulfur detector) loses sensitivity. I wonder what might be causing this problem.

[muGC]

With the little information supplied, it's likely a combination of 1) your column bleed is coking the ceramic tubes or 2) your sample is very "heavy" and is coking the ceramic tubes.

Has your column been properly conditioned so the baseline rise on the SCD at 360 C is minimal? The SCD is very sensitive to column bleed.

[Ana Paula]

Yes, the column was conditioned with 360 ° C. Someone already had the sensitivity loss problem in sulfur detector 355? The silica may be interfering in the detector sensitivity?

[muGC]

What is your definition of conditioning the column? What are the specs of your column?

Who hasn't had a sensitivity loss problem with a 355 SCD at one point?

[Ana Paula]

The column is that I use Agilent - DB-5MS (Length - 30m / Diam - 0.250 mm / Film 0,10μm).

[muGC]

How long was the column conditioned at 360C? And was the column connected to the SCD during conditioning?

I would suggest the following:
1) condition the column more, but have it disconnected from the SCD
2) replace the ceramic tubes in the SCD burner

[Ana Paula]

During the conditioning the column was not connected to the detector and SCD ceramic tubes are new. The problem is that I made standard injections repeatedly and the sensitivity drops and the value of the area decreases.

[Andy F]

You could try turning the hydrogen off to the SCD between injections, while the GC is cooling.

[Ana Paula]

Every time the GC is not running hydrogen is off. I wonder if the silica may impair the performance of SCD and therefore lose sensitivity. Know someone who has been through this sensitivity loss problemo at high temperatures?

[muGC]

Every time the GC is not running hydrogen is off. I wonder if the silica may impair the performance of SCD and therefore lose sensitivity. Know someone who has been through this sensitivity loss problemo at high temperatures?

Please read my first response again. Column bleed cokes the ceramic tubes causing impaired sensitivity. You must not have conditioned your column properly at your final run temperature. It is the column phase, not silica, that is the problem.

What is the purpose of your method going to 360 C?