Steve_hi
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calibrating pipettes
I bought a toppette brand 100ul-1000ul pipette and when I went to calibrate it the spring retaing nut had to be completly backed out no way to leave
it in even just a little. Needless to say it's made in China. Has any one here ever had this problem and what is your solution to remedy it. I had to
back it down to 675ul in order to get 1 ml I used a balance and distilled water to calibrate with, 1g per ml.
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Steve_hi
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[img]http://C:\Users\Steve\Pictures\Manual-Adjustable-TopPette-Pipette.jpg[/img]
I found out why my pippette wasn't able to be calibrated. It was my own ignorance. I didn't receive any instructions with it so I didnt realize that
you had to stop pushing the plunger when it came to a 'first stop. But you go all the way with the plunger when you are expelling the sample. it works
perfect now. It is very handy, especialy when doing serial dilutions and you need ten different samples
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Sublimatus
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I love those things.
There's something about the thought of being able to dispense 0.5 μL accurately that gives me a nerdgasm.
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bahamuth
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Quote: Originally posted by Sublimatus  | I love those things.
There's something about the thought of being able to dispense 0.5 μL accurately that gives me a nerdgasm. |
Well, at those volumes the best pipettes are around 5-20% off, which is incredibly much if you start with a strong stock solution. They are made for
biology, which is stone age chemistry when it comes to accuracy of concentrations. Repeatability is a drag too, one have to use it everyday almost,
with perfect technique, and the same solution to get good results. Believe me, I've been pipetting for three years+ straight working with sensitive
stuff like next gen sequencing.
I'd even go so far to say that an experiment in molecular biology "must" be done to completion by the same person, if they are using pipettes, as
there are literally thousands of different techniques when all "fingerspitzengefuhl" and subtleties of that particular pipette is used.
Any sufficiently advanced technology is indistinguishable from magic.
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Steve_hi
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If you don't think that pippettes are very useful or accurate what method would you sugest for volumetric measuring?
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phlogiston
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Bahamuth is right, and often perfect accuracy is not necessary. The fact that in molecular biology work, where such pipettes are common, most
protocols still work fine showing how non-critical these things usually are. Most such labs do not even calibrate their pipets at all, or only with
large (and often random) intervals. I work in molecular biology and analytical chemistry labs and the analytical labs are filled with good old
fashioned glassware, in addition to volume-displacement pipettes which are only used when accuracy is less important.
Volumetric glassware achieves better accuracy (0.2-0.02 %) for larger volumes (5 ml and up). If you need to accurately determine the quantity of a
very small amount of liquid, a good scale does a much better job than air-displacement pipettes (in fact, I pipet water of a known temperature onto a
scale to calibrate my pipettes. For the smallest volume pipette (10ul), a scale accurate to .01 mg is required).
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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feacetech
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| Quote: Originally posted by Steve_hi | | If you don't think that pippettes are very useful or accurate what method would you sugest for volumetric measuring? |
Class A glass and serial dilutions
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