I've just started using a new microscale thermophoresis gadget to get some protein:protein Kd's. However, I'm running into some problems with the serial dilutions of my unlabeled sample. It's a super-sensitive instrument which is great, but the sensitivity means very small differences ruin data quality.

Are there tried and true methods for keeping dilutions as perfect as possible or ways to prevent protein adsorption to eppendorf or PCR tubes? I've added 0.05% Tween-20 and that's helped. It very well may just be my pipetting technique and how much of the tip gets submerged at each step. I'm working with volumes around 20-40 uL and have been using low-retention tips on a P20. I'm all for silanizing or BSA-treating tubes, but I'm hoping to avoid adding more variables.

Any tips?