Hi Ritesh, are you interested in compounds which are not ionizable using *any* of the 3 techniques or in compounds which may be problematic in one but measurable in another technique?

Also, the answer will be yes, there is always something remaining undetected. It would be easier to get meaningful reply asking for specific compound classes. Bests, Jan

apology for not mentioning specific question. just wanted to know on what principles does it depend on or characteristics of molecule to get it ionized in any of the technique and just to specify Polycyclic aromatic Hydrocarbons,which Mode gives good ionization like ESI or APCI ?

Hi Ritesh,

to understand the general principles of different ionization technologies and its implication on chemical classes I am afraid this forum is not the right place and you have to get back to text books instead.

Regarding PACs, you are probably best of with using GC-EI because this is a hard ionization. You will get some signal in LC-ESI (at least I do), but due to their chemical nature (no -OH, -SH, -NH groups) PACs are not as easily protonated as other compounds.

Bests, Jan

Hi Ritesh,

additional to Jan suggestions you can use two different techniques: 1. APPI (Atmospheric Pressure Photo Ionization 2. Fluorescence Detection. With both techniques you can analyze PAC's by using LC/MS.

Regards

Markus

http://www.lcms-connect.com/uploads/tx_phdpagilentmediacenter/5990-9230EN.pdf

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@Mr.Jan.. what about APCI ? do you have an idea related toPAH ionization in APCI ? . kindly suggest me some books which involves study of Leachables (impurities from CCS) ionization in LCMS. that would be a great help. thanks a lot for all ur time

@Mr.Markus.. m aware of FLD.. let me try APPI .. thanks a lot .. appreciated your kind help

From my experience APCI can work fairly well with PACs. I didn't have much luck using ESI but this might depend on the compound and parameters of the measurement.