Sulfur impurities in Ethylene by PFPD detector

[mr3573]

I know a PFPD detector isn`t a linear detector and have a question for calibration. I have only one standard that mean one level calibration in 10 ppm. The software has some choices in calibration menu. Is it mandatory to select “quadratic” equation? in this case I should select “include origin” too. The real sample usually has lower concentration (below 1 ppm). Can I use “linear equation” for calibration?
Also another problem is big negative peak in PFPD detector for ethylene sample. is it a practical way to eliminate negative peak of ethylene which is main component?

[AICMM]

mr3573,

Over short ranges, even quadratic approximates linear. The question is, where you on that curve. The other question is, what are you regulated on? If only over 10 ppm, you have the standard and you can be confident, if much lower than that you should probably invest in some more standards.

The negative peak you see is quenching of the detector by the ethylene and you cannot eliminate that with PFPD. That means you have to start looking at the chromatography to solve this if it is a problem.

Best regards,

AICMM