SCD

[lynoguchi]

I have a SCD equipment with a chromatograph.
But, I have a problem, in the first injection, the peaks appears normally, but from the second, the peaks desappear.

Do you have a theory about this?

Thanks

[aldehyde]

what are the peaks?

[lynoguchi]

Sulfur compounds, like H2S, COS, methylmercaptane.

[aldehyde]

What are you using to inject sample? A gas tight syringe, valves, what kind of inlet? What carrier gas?

[lynoguchi]

I´m using a GSV, but before the valve, I'm using a inox tubing.
The carrier is Helium, but I only pass the gas sample through the tubing and valve, without carrier.

[AICMM]

lynoguchi,

How old is your SCD? The older SCD's had a problem of reactive furnace tubes that would basically start to gobble up sulfur compounds from the very start.

Best regards.

[lynoguchi]

The SCD is new. It was installed 2 months ago.
But I think the problem is the ceramic tube for pyro.
Maybe I need to change it?

[AICMM]

lynoguchi,

Based on my limited knowledge of SCD, I would suggest replacing the tube as the starting point. Unfortunately, I do not have hands on with this detector although I hope that is about to change.

Best regards.