We use kinetic turbidimetric method for BET of parenteral products. OOS occurs every now and then on CV% values, endotoxin standards and PPC% but lately it got worse. The only reasonable explanation I can come up with is pipetting error caused by analyst. Training of analyst repeated, pipette’s calibration and performance checked, disposal materials checked, it all seems fine. I failed to find root cause and out of ideas.
I would deeply appreciate if you’ll leave any lead to follow.