Chromatography Forum

Could someone sum up their similarities differences and applications for each?

Why would one prefer the one over the other?

Any reading suggestions?

NPD does phosphorous and nitrogen compounds
FPD does sulfur and phorphorous compounds

NPD is very sensitive but unstable. A new bead takes at least a day to Break in and stabilize and lasts constant running a few months before you need to replace. I wouldn't use an NPD without an internal standard to compensate for bead issues.

FPD I am not too familiar with but I am pretty sure it is more stable.

NPD for Nitrogen and Phosphorus, buy one from a manufacturer that does not have such delicate beads

FPD Dual Flame, old reliable technology note the response to Sulphur is non linear and the GC should include a Linearising facility.
PFPD Pulsed version of the same , claimed to give better sensitivity for Sulphur but can also be tuned to other elements too.

NPD/FPD in environmental now often replaced with MS

NPD, almost never seen one used for Phosphorus, mainly used for Nitrogen all applications.

FPD, not seen much now, very low levels are handled by SCD (Sulphur Chemiluminescence Detector) Largely replaced by MS based methods for environmental work

mariosapm,

Selective Gas Chromatographic Detectors, , Dressler, M; Elsevier, ISBN 0-444-42488-1

Detectors for Capillary Chromatography, Hill, H, McMinn, D.; Wiley and Sons; ISBN 0-471-50645-1

You can also get DET notes from Detector Engineering and Technology (www.det-gc.com). They make an NPD among other detectors based on the same design. They will also have a lot of comments on how to optimize your NPD if you should choose to go that route.

FPD subject to quench when the compound in question comes out underneath a hydrocarbon of significant concentration. If you are trying to do a bunch of sulfurs, this can be very problematic unless you matrix match. As noted an SCD might be a good alternative here but it is very pricey.

NPD, from what I have seen, has very good selectivity.

Best regards,

AICMM

thank you very much. I'll look into getting my hands on those books.

FPD also can be used for tin, in addition to sulfur and phosphorus. FPD actually is more unstable than NPD (at least in my experience) as it will bounce around a lot without much rhyme or reason, where NPD will stabilize out once the bead gets worn in, and slowly drop down over time. NPD also is more expensive due to consumables. If you change solvents a lot you should also consider that might require changing types of beads as well for the NPD.

I find FPD to be incredibly selective and sensitive, and use it a lot. It has the same level of sensitivity as MS for the most part, and I have gotten down to the ng/mL range for elemental phosphorus. FPD is relatively rare, and not as many people make them as NPD.

In my line of work, I only use NPD for nitrogen compounds, and FPD for sulfur, phosphorus, and tin.

why don't you use your NPD for phosphorus as well?

I've used the NPD for pyrazines on a 6890GC. As I said the beads are delicate and have a finite lifetime. Agilent makes a white bead which is more sensitive to nitrogen and a black bead which reduces tailing for phosphorous compounds but is less sensitive (I think 10 fold) to nitrogen comounds as a trade off. We always had better sensitivity to pyrazines (using headspace SPME) on the NPD vs MSD which is why we used it. Resolution was a issue but we just reported total C1, C2, and C3 substituted pyrazines as many of the isomers could not reliably be resolved.

I have heard about the nitrogen chemiluminescence detector but don't know how it compares but I suggested looking into it.