Dilution capacity

[smartin]

Which could be the reason if the capacity of dilution of a method doesn't work?

I mean that I have my LC-MS/MS method, with good precision, accuracy, selectivity….. But if I dilute a sample it doesn’t report a good result….

Can anybody help me??????
Thank you!!!

[Steve Reimer]

Is it an internal standard method?
If so has the internal standard level been adjusted to reflect the dilution?
If no internal standard, have you diluted out something that suppresses (or enhances) your signal?

[smartin]

Great !!!
It is an IS method, and I didn’t adjusted the internal standard.
But how I have to do this adjustement? Adding the half, if I am doing a dilution ½????

[JGK]

Great !!!
It is an IS method, and I didn’t adjusted the internal standard.
But how I have to do this adjustement? Adding the half, if I am doing a dilution ½????

The simlpest way is to make a diluent with the same concentration of IS as your extracted sample. That way you can perform any dilution you want,

[smartin]

Sorry.....
but I can't understand why it is and why to do it....

[tom jupille]

Add the internal standard *before* you dilute. That way the effect on the analyte and on the internal standard will be the same (that's actually the whole point to internal standards).