Improving Mass Spec linearity

[wrufai]

Hello,

Are there any tricks to improve calibration curve linearity? I typically run standards from 10 to 10,000 ng/ml and usually have to drop my two highest points do to possible over-saturation even though my ULOQ only has counts around 100,000. I use a triple quad for sample analysis and see this phenomenon across different molecular compounds.

Thanks for the suggestions.

[brewer]

A couple of questions:

Do you see this in neat solution as well as in extract?
Have you tried a different ionization mode?
Which triple are you using? When running the API5000 I typically see saturation at 500ng/mL, which is why I prefer a 4000 or even a 3000.

Even still, 100,000 counts at 10,000ng/mL is very low. Are these compounds typically hard to ionize (how does the tuning go?)

Finally, have you been able to replicate this phenomenon on a different instrument?