Chromatography Forum

What do you all think is the best detector for Sulfur ? Our SCD is brand new 8355 with 8890 and still have issues with repeatability. One of our clients spec is 0.1 ppm max so we opted for SCD. Do you think FPD or PFPD better than SCD ?

I suppose it depends on your limit of detection. For sensitivity, it's difficult to beat a SCD that's working properly.

However, if you don't need to see a "gnats hind end" of stuff in your sample, the FPD is a good option. I use SPME to sample the headspace above my samples and 100 ppb of something like dimethyldisulfide at 100 ppb in beer would blow my FPD out of the water. I'd have to split the injection.

FPD operates like a FID so maintenance and operation is easier than the SCD. My motto is to use the simplest tool to answer the question.

Thank you rb6bano for your reply. We had 6890 with 350B sievers SCD. it worked fine for years and all of a sudden it died, that's when we got this new 8355 SCD, it never worked right since day one. Always had issues with repeatability even after changing everything to Sulfinert stuff. It has been two years and we still have issues with this detector.

What makes you think that the repeatability issue is due to the detector?

Once the SCD gets lined out, it just sits there and waits for sulfur compounds to come. I would suspect something in the transfer of sample to the column and through the GC is your problem.

Are you injecting liquid or is it some type of headspace analysis?

Sorry, I thought I had replied already. We used to run lot of aromatics before on liquid injection but we dedicated this GC for natural gas samples only. It could be like you said but vendor said it is the detector that is causing the issue, I do not remember the exact issue as we did tons of things on it to get it better.

Visa,

my experience has been that most rugged is fpd but not as sensitive as SCD. That being said, the SCD I work on has been extensively modified to provide better reliability. Users turn off hydrogen at end of analysis sequence, ceramics have been modified, and bakeout procedure implemented. Otherwise, the sensitivity would drop off too quickly to be of any use.

Issue with fpd is that chromatograpy has to get the sulfur compound clear of the hydrocarbons or quenching will kill you.

Best regards,

AICMM

Got it. Thank you. we have been turning off H2 after the run. I have created a standby run and it turns off hydrogen and saves helium as well.

Visa,

my experience has been that most rugged is fpd but not as sensitive as SCD. That being said, the SCD I work on has been extensively modified to provide better reliability. Users turn off hydrogen at end of analysis sequence, ceramics have been modified, and bakeout procedure implemented. Otherwise, the sensitivity would drop off too quickly to be of any use.

Issue with fpd is that chromatograpy has to get the sulfur compound clear of the hydrocarbons or quenching will kill you.

Best regards,

AICMM