With a modern run-of-the-mill triple quad, under reasonable LC and source conditions and negative ion mode, I have seen similar polyphenolics give responsive full-scan extracted ion chromatograms with S/N >3 at ~ 50-500 ng/mL (ppb), roughly.

However, metal ion complexation of polyphenolics is known to occur and will likely significantly change the ionization efficiency and spectra.

See  "Electrospray mass spectrometry and UV/Visible spectrophotometry studies of aluminum(III)-flavonoid complexes" Deng, H; Van Berkel, G. Journal of Mass Spectrometry (1998), 33 (11), 1080-1087

as well as

"Enhanced detection of flavonoids by metal complexation and electrospray ionization mass spectrometry." Satterfield, M; Brodbelt, JS. Analytical chemistry (2000):  72(24), 5898-5906.

Thank you Luke, this is very helpful. I will have a look at those papers.

HI, Manda, I agree with Florian. For LCMS, full scan always give you lower sensitive, SIM (selective ion monitoring) mode give you better sensitive and even MRM (Multiple Reaction Monitoring) give you much better sensitive, typically sub-ppb level. As soon as you  know the compounds you are looking for, you can either use SIM or MRM to obtain better LOD

Yes, I agree that MRM would be the way to go in future. However, at the moment we are still getting to know our matrix. Even though many of the compounds in our samples are known and we could therefore target them, I can see that there are many more that we are not able to see clearly in MS fullscan. Once I have a nice fullscan TIC I will be able to do some nice fragmentation work on the visible peaks to aid identification and more specific screening. However, if you don't see the peaks in MS, how can you make further progress? Then there are also some applications we are faced with at my place of work where we need to try to find out why a certain sample is different from another. I guess sometimes a targeted MRM screening will be able to identify the source of sensory differences, but usually the situation is much more complex. Usually in these cases you need a thorough screening that shows as much as possible peaks in each sample as a profile so that one can compare the various profiles and try to identify a biomarker.

An MS is supposed to be able to do fullscans and is advertised as such. Therefore it is important to make sure why an instrument is not able to optimally perform one of its functions. In our case there is a real metal ion contamination coming from somewhere in our system which is making it impossible for the MS to perform optimally in both fullscan and MRM mode. The effect on the fullscan is much more severe though, but we can not continue working like this in MRM mode and pretend everything is honkey dorey. So, now we need to clean up as much as possible and I need to get decent specifications for a typical triple-quad so that we can have an idea if our system is performing all its functions as it is supposed to be. We did pay for that. We do have MRM specifications but this is not helping because it is too selective. All the MRM specs passed even though the system is heavily contaminated. Unfortunately most suppliers of triple quads do not have fullscan specifications. So, no one knows what their instruments can do in fullscan or if there is contamination. That is why I'm trying to get as much as possible information from fellow scientists and research papers and have found several papers that show the fullscan ability of triple quadrupoles.