New results. (analysis: standards; samples (DB and FS); Calibration blank (auto zero); standards; standards)
Conclusion: happening the opposite. I'm still having a drift of the signal but negative this time!
The set of results (2nd standards) in between, are too much lower.
I ran my standards and samples three times and only the first one had R^2>0,995... So, calibration blank between samples and 2nd reading of standards, makes a difference but it doesn't solve my problem, example:
look at this: (1st and 3rd reading of standards; 3rd repetition)
It seems that auto zero "cleans too much" both nebulizer and burner, but if I doesn't aspirate any water I "get more iron" than it is supposed to... strange isn't it? Maybe not, I need to find a compromise between this two situations.
This was a great *delete me* Thanks.