Pipette verification tips

[RR1]

Does anyone know where to get hold of pipette verification tips, to allow a quick check of dispense volumes?

Thanks

[TimOz]

Hi Rashmi,

I don't know what you need here. For pipette verification we have to use the tips we routinely use and use a weight based assessment of repeated dispensings ot a dye dispense into a spectro cuvette. What exactly do you need to do?

[Lcsmrz]

Each manufacturer has a preferred procedure for using their pipettors and usually has a suggested verification schedule and method.

ISO also has a great document on verification of air-displacement pipettors, but I don't have the number with me today.

[RR1]

I was informed that pipette verification tips -which are pre-marked with dispense volumes could be used to perform a quick (rough?) daily/weekly check, in between the quarterly/ annual verification performed by the weight based assessments.

This would just highlight any pipettes that could be losing calibration sooner so they could be re-calibrated prior to the scheduled date.

[TimOz]

I have never heard of this. I guess they may be useful if a pipette seal has failed and the volumes are way out but I would not call that a volume verification. There are pipette leak detectors that check fot a seal problem. Look here:

http://www.pipettesupplies.com/shop/Pipette-Leak-Detector-p-16224.html

Over to someone else for pipette tips.

[RR1]

Thanks Tim and Lcsmrz, I'll try and find out some more details from my QA in the next few weeks. I suppose I could mark a batch of my own tips using a newly calibrated pipette, and then check all my pipettes weekly to see if they are still in range....but a bit of hassle doing this.

Of course if we perfomed quarterly in-house calibrations, and these did not show a significant change between calibrations that would be ok.

However, if one of your pipettes failed calibration how would you deal with all the testing performed prior to the failed pipette calibration (I suppose the controls run would justify the results??), Just thoughts!!!

[Malcolm Needs ☆]

It seems to me that it depends for what you are using the pipettes.

If it is for serology, as opposed to making up reagents (including red cell dilutions), if your pipettes are way out, your controls will not work (although the ratio of the volumes are still going to be okay in most cases).

[L106]

Granted, we rarely use pipettes, and when we do we just borrow them from the Serology Dept (who calibrates/verifies them), but how often do your pipettes fail their quarterly or annual check?

I'm sure that nowadays we are using fancier pipettes designed to deliver more precise amounts in more critical testing procedures, because back in my early days in the general lab we didn't "calibrate" pipettes, and I don't think we killed anyone.

[Malcolm Needs ☆]

.....because back in my early days in the general lab we didn't "calibrate" pipettes, and I don't think we killed anyone.

Ah, but nowadays, you have to be able to prove why you haven't killed anyone, including the bits that are totally and utterly irrelevant.

Yes, without doubt, we did need to improve our Quality Systems, but now the world has gone completely "Quality Mad", and it has become thoroughly intrusive, to such an extent that it is preventing people doing things that actually help patients (which is our raison d'etre).

:mad::mad::mad::mad::mad:

[RR1]

OK ,I like the comments so far, so will ditch this idea for the time being. Following on from what Malcolm has said, I have to admit I think I've forgotton how to use a pipette, been off the bench too long doing 'Quality stuff'!!!!!.

[L106]

Ah, but nowadays, you have to be able to prove why you haven't killed anyone, including the bits that are totally and utterly irrelevant.

Yes, without doubt, we did need to improve our Quality Systems, but now the world has gone completely "Quality Mad", and it has become thoroughly intrusive, to such an extent that it is preventing people doing things that actually help patients (which is our raison d'etre).

:mad::mad::mad::mad::mad:

Amen!

[TimOz]

"It seems to me that it depends for what you are using the pipettes.

If it is for serology, as opposed to making up reagents (including red cell dilutions), if your pipettes are way out, your controls will not work (although the ratio of the volumes are still going to be okay in most cases). "

Malcolm,

I agree with this statement in general - except in Immunohaematology labs. I have had a bit to do with designing controls and many blood bankers really do not understand their test performance, so they do not understand using controls in red cell serology. Here is a classic example: Someting as robust and simple as a vial of monoclonal Anti-A can be damaged by a whole range of things like bacterial and reagent contamination, poor transport and poor storage. What do we QC it with? an A2 cell (or an A2B cell if we are diligent). The reality is that a good brand of Anti-A can loose 95 to 97% of its activity and still give a score 4 with an A2 cells but fail to detect an A3 cell. This is not really controlling the test at all.

I have even had people say to me that they want a "slam dunk" control i.e one that always works no matter what the test performance is so they can get a QMS pass. Whew!

Back to Rashmi's original question. I have seen air displacement pipettes with dodgy seals that would pipette perfect volumes but sometimes fail and pipette less or nothing. This is usually a broken O-ring and it can be a real pain when it is in a multi-channel pipette used for EIA. I guess this is what the leak detector mentioned above is supposed to detect.

[Labstream]

Many people used to use "graduated pipette tips". Do a search on Google and you'll still find suppliers. Two reasons they aren't used anymore: 1. They are accurate enough and 2.Nobody bothered.

The world is now quality and traceability crazy and there are many forces in play to monitor and control risk areas (clinical, pharma manufacture etc). Pipettes are no exception. Some people use in-house colorimetric systems (the creation of these then need quality controlling - the proverbial piece of string) or commercial systems such as Artel, but these can be very expensive and are not recognised by varying quality bodies due to corrleation with the gold standard of gravimetric/weighing technique.

Easiest is to use a balance (also checked) and de-ionised water, and use a simple spreadsheet with Z factor correction etc and record the results. As for leak tests; put the manufacturers tip on the tip cone and aspirate the full volume, see it is drips.

I have seen quite a few pipettes in serological labs over the years delivering over 10% error, so 90Ul instead of 100ul for example. The results can be signficantly wrong especially using commerical test kits. Add to this the wrong tip, filter tips, poor techniques and the errors can increase!

This last bit is what the lawyers like!!