Pesticides Recovery- Agilent 6460

[cott1]

Hello, All
I am a newbie here . Getting up pesticides program in juices in my lab. Got Agilent 6460 Jet stream. Using Quechers extraction.
I use TPP as Isdt and introduce it after the extraction . All calibrations are matrix matched ( 5-50 ppb six point cal.) I have problem with my recovery studies- For some reasons I am on the higher side ( 130% ) ... trully belive that it is my Istd overcompensating effect. What concentration of Istd do you use? I use 25ppb- maybe too low?? seems that instrument is too sensetive to the smallest changes... ( I use fast switching capillary) ..clean after each batch ...
All advices are really appriciated.
Thank you

[dr_bahram1977]

maybe you've a hidden concentration afterwards. check to see if you put samples open for evaporation? this may cause for 130% recovery.

[richiekichi]

What recoveries do you get without IS? Like the previous poster mentioned make sure all your calculations are correct, that you're applying the correct multiplication/dilution factor. You've got a good standard range there, check your calibrations settings are appropriate. I ain't a fan of forcing the origin through zero. But use whatever works for you.