Quantify Norethisterone in fg levels

[Vidal]

I need quantify Norethisterone in fg levels.
Which triple quad is the most sensitive and robust between Agilent, Applied Biosystem and Waters?

[Schmitty]

Applied Biosystems has an application note:

HERE

They list a detection of ~1ppt in water. It's a start, I guess.

We have ~30 ABI instruments here, all with good reliability (and in-house service ).

[yangz00g]

I would say API 5000 if according to sensitivity only.

I would also appreicate any comments on the robustness of API5000 since no skimmer cone is used, e.g., is frequent cleansing of Q0 needed? Thanks in advance

[dr_Pyrex]

Can you describe matrix for norethesterone determination?
This is food analysis or environmental analysis?