Chromatography Forum

What temperature is your lab at? It's all very well specifying a water temperature, but you might be adding an extra hurdle for your efforts if the water cools off as you're making your determinations

Hi to All,

if i may add a word, the main problem is not the pipette calibration itself, but the way pipettes are actually used. at Andrew Alliance, http://www.andrewalliance.com, we have developed a robot using manual pipettes according to the famous SOPs, and we discovered a number of incredible details. For example, many manufacturers hide a well known phenomenon: the pipetting, depends on your strength! I am not speaking about the speed of the thumb, that obviously affects the performances, but even the force of the thumb to detect the first stop is totally subjective. Calibration labs know perfectly that some operators have a heavy thumb, and some others have a light thumb....and the calibration outcome is different! so, imagine what happens: you can follow SOPs, and the pipette has been calibrated by a "light" thumb and it happens you are a "heavy" thumb...

It's indeed to solve this type of problem we have developed Andrew, the pipetting robot that uses manual pipettes. And i can tell you that his thumb, chosen to be a "medium" thumb, is always the same

Best,

And i can tell you that his thumb, chosen to be a "medium" thumb, is always the same

Now someone is going to request that a "thumb calibration device" be developed and included in QA

Update: QA is now relaxing to allow risk-based management. This would be a weekly check, so worst case scenario upon a recheck would be that one week's data would be suspect. They say we can specify in the SOP to use 25C water because there is a 25C calibrated water bath, without having to delve into the details.

I haven't asked them if a week is Monday through Friday, Monday though the next Monday, or exactly 7.00 days from the time of last check. I think we can do 4 weighings at each of low, middle, and high ranges of the electronic pipet, and everyone will just use the same unit during that week for stuff that affects the data (like a sample aliquot, not addition of a reagent).

I like the risk-based approach and I've seen similar approaches as you suggested with performance checks on pipettes used for only samples and not reagents. I suggest to include a table of water density in the SOP and test at "room temp" with a measurement of the water temp using a calibrated thermometer. You would still need to check the water temp even if using a calibrated water bath. For example you place a beaker of water in calibrated water bath, at what point does the water in the beaker reach 25C?

I suggest a 7 day expiration to keep it simple.