Hello, I am trying to qualify my Human Serum liquid class by gravimetry on my STAR, 8 channels. I have 3 types of tips: 50uL, 300uL SLIM TIPs, and 1000uL Tips, non filter, CO-RE II. I am trying to qualify at the following volumes:
50uL tips: 10,20,30,50
300uL: 30,50,100,200,300
1000uL: 50,100,250,500,1000
I am dispensing in dry tubes with canonical bottom. It passed beautifully for PBS (3 replicates for each, CV and bias below 1.5%).
I am now trying some human serum. No matter what I do (Jet dispense, Surface empty, forward pipetting, reverse, adjustment of parameters etc), I get inconsistant biais and CV up to -7% / +7%. It looks totally random.
DO you guys have any insight or liquid class you could share?
Hi Kevin. I would not look at the bias until you have an acceptable CV among your replicates. In my lab, we use an integrated balance inside the Hamilton, to reduce the environment effects when doing gravimetric testing (affecting mainly bias). And I do at least 5 replicates. The CV is always good, when using fresh tips. Even for 10 uL serum/plasma with 50 uL tips. Our acceptance is +/- 3.5%. I barely have problems with CV. My suggestion, please check your test system or that you are using fresh tips.