Repipet calibration?

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

14 posts Page 1 of 1
We are contemplating if according to NELAC standards recalibration of repipet's are needed at our lab. We use them to dispence volumes with precision. For example in EPA 515.4 we use them to add about 2 ml H2SO4 to lower the pH to <1, add the 5 ml 90% hexane/MTBE wash, and the 4 ml extraction solvent containing internal standard.
I am discussing the use with our QC/QA guy and take the stance that calibration is not needed.

How do you folks deal with this issue?

Thanks
Bear
Do you check the dispensed volume with a calibrated or class A volumetric? If so, you may be OK.
We have several prep methods that use this and QA is fine with it.
Yes, we are NELAC (TNI) certified.
One of my test sample is viscous, I need 1 mL, 2 mL, 5 mL, 10 mL and 25 mL TO CONTAIN pipette, I have not found any vendor locally, do you any international brand for these pipettes?
We provide fast success in Braindumps.com dumps exam by using our high quality 300-208 dumps prep
Andersan wrote:
One of my test sample is viscous, I need 1 mL, 2 mL, 5 mL, 10 mL and 25 mL TO CONTAIN pipette, I have not found any vendor locally, do you any international brand for these pipettes?


Welcome to the forum.

Rather than struggle with volumes, use mass and calculate for the actual masses used. You will get much better repeatabilty and accuracy.

For future reference - you will get more answers quicker if you start a new thread.

Peter
Peter Apps
Steve Reimer wrote:
Do you check the dispensed volume with a calibrated or class A volumetric? If so, you may be OK.
We have several prep methods that use this and QA is fine with it.
Yes, we are NELAC (TNI) certified.


Checking it by mass is quicker and more accurate and precise.

Peter
Peter Apps
Weighing a 1 mL volume of a volatile solvent (DCM or methanol) in a fume hood is not as quick as dispensing to a 1 mL vol flask.
Steve Reimer wrote:
Weighing a 1 mL volume of a volatile solvent (DCM or methanol) in a fume hood is not as quick as dispensing to a 1 mL vol flask.


That depends a lot on technique. Septum caps make a huge difference; APPS, P.J. and ARCHER, M. 2010. Evaluation of the source of bias caused by losses of solvent vapour during sample preparation. Journal of Accreditation and Quality Control 15: 171–180.

Methanol is pretty tractable - reasonable boiling point and a low molar volume in the liquid phase.

Anyway, Bigbear wanted to use volumetrics to check his pipetting - checking them by weighing is much much faster - just tare a container, dispense, weigh. Even with a bog standard 1 mg balance you have microliter precision, which you cannot get with volumetric glassware except at the marked volume and with small volume flasks.

Peter
Peter Apps
Guess we will just clean out the re pipets and check them with water/mass quarterly!
Bigbear wrote:
Guess we will just clean out the re pipets and check them with water/mass quarterly!


This is what we implemented to satisfy NELAC auditors. It is a pain to flush out bottle top dispensers with water, dispense and weigh water, then switch them back to solvent, but it was the only way to avoid repeat findings :( It is not so bad for the Eppendorf/Rainin repeating pipettes though. For most of those we do the check daily then send them off once a year for recalibration, which to me makes no sense since they are still passing the calibration checks.

We also have to send the NIST certified weights off once a year to have them recertified so that we can continue to use them to check balance calibrations before we check the pipettor calibrations.

I am ok with traceability, but I am afraid one day there will be auditors asking for the lot number of the toilet paper used to "maintain" the analysts the perform the tests. :lol:
The past is there to guide us into the future, not to dwell in.
James_Ball wrote:
I am ok with traceability, but I am afraid one day there will be auditors asking for the lot number of the toilet paper used to "maintain" the analysts the perform the tests. :lol:


And the auditors will someday "need" to know:
supplier name
supplier part number
whether the paper was installed "over" or "under"
how many sheets were used
how many wipes
There is a great book by Dr Seuss that relates to the topic of certification.


“Oh, the jobs people work at! Out west near Hawtch-Hawtch there's a Hawtch-Hawtcher bee watcher, his job is to watch. Is to keep both his eyes on the lazy town bee, a bee that is watched will work harder you see. So he watched and he watched, but in spite of his watch that bee didn't work any harder not mawtch. So then somebody said "Our old bee-watching man just isn't bee watching as hard as he can, he ought to be watched by another Hawtch-Hawtcher! The thing that we need is a bee-watcher-watcher!". Well, the bee-watcher-watcher watched the bee-watcher. He didn't watch well so another Hawtch-Hawtcher had to come in as a watch-watcher-watcher! And now all the Hawtchers who live in Hawtch-Hawtch are watching on watch watcher watchering watch, watch watching the watcher who's watching that bee. You're not a Hawtch-Watcher you're lucky you see!”

From ― Dr. Seuss, Did I Ever Tell You How Lucky You Are?
qui audit auditores ?
Peter Apps
Good ones, I've been claiming those thoughts about the TP!
The main thing that "frosts" me about our last audit was the auditor did not understand our organic methods!
James_Ball wrote:
Bigbear wrote:
Guess we will just clean out the re pipets and check them with water/mass quarterly!


This is what we implemented to satisfy NELAC auditors. It is a pain to flush out bottle top dispensers with water, dispense and weigh water, then switch them back to solvent, but it was the only way to avoid repeat findings :( It is not so bad for the Eppendorf/Rainin repeating pipettes though. For most of those we do the check daily then send them off once a year for recalibration, which to me makes no sense since they are still passing the calibration checks.

We also have to send the NIST certified weights off once a year to have them recertified so that we can continue to use them to check balance calibrations before we check the pipettor calibrations.

I am ok with traceability, but I am afraid one day there will be auditors asking for the lot number of the toilet paper used to "maintain" the analysts the perform the tests. :lol:
I can see testing disposable tip repipettors by weighing with water. I do this each day that I use any particular repipettor at its volume or setting.
But having to empty out bottle top dispensers to check them with water for delivery by mass, seems over the top. For Bottle top dispensers I pick a setting that is a muntiplication factor for a volumetric setting, and then check filling the volumetric to the mark. I make adjustments until I can hit the meniscus mark. For example it takes me 5 pumps of my 2mL fixed volume hexane to fill a 10mL volumetric. It takes 5 10-mL pumps of my Methanol bottle topper to fill a 50mL volumetric. I also tare 5 VOA's and then dispense 5 separate aliquots and weigh each VOA back to check for precision.
14 posts Page 1 of 1

Who is online

In total there is 1 user online :: 0 registered, 0 hidden and 1 guest (based on users active over the past 5 minutes)
Most users ever online was 599 on Tue Sep 18, 2018 9:27 am

Users browsing this forum: No registered users and 1 guest

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry