MathBench > Measurement

Basic Lab Techniques

Lab Bench Tool of the Day: The Micropipetter

How to select a micropipetter

exploding pipetBefore we start, I want to emphasize the importance of this topic. Improperly-used pipetmen have been known to explode on contact with hard surfaces, burst into flame while sitting unattended on conference tables, cause rashes of shark-bite reports, and even destroy the inner workings on the expensive pipetman, annoying your hard-working TA.

OK, now that I have your attention.

  1. you need to know which pipetman to choose.
  2. you need to know how to interpret the numbers on the volume indicator.

There are 3 standard sizes of pipetman, called a P20, a P200, and a P1000. They measure up to 20, 200, or 1000 microliters, respectively. The rule for choosing between them is simple: use the smallest pipetman you can, but don't exceed the capacity of the pipetman.

milkFor example, say you need to measure out 25 microliters of a solution. 25 is too big to fit into a P20, so DON'T DO IT, ok? 20 will fit in a P200 or a P1000, so pick the smaller one. That way you'll get a more precise measurement.

Here's an analogy. Say you need to measure ½ gallon of milk. Which would you rather use, a one-gallon jug, or a five-gallon bucket? Right, the one-gallon jug. Pick the smallest measuring device that will hold the quantity needed.

tipsOh, yeah, then get the tip. This part is easy because they're color-coded.

Not exactly rocket science.

Quick check

Which pipetman would you use for each measurement?

Turn on javascript to make this table interactive.

Which Tip is Which?

Tips

 
P20
P200
P1000
Some superfast glucometers require as much as 25 microliters of blood. Which pipetman would you use to measure this amount? 25 microliters won't fit in a P20, so you have to use the P200
P20
P200
P1000
Part of the process of making glucose test strips for diabetes involves pipetting 210 microliters of glucose oxidase into the reactive mixture. Which pipetman should be used for this purpose? 210 microliters won't fit in a P200, so you have to use the P1000
P20
P200
P1000
People with diabetes need to measure their blood sugar using a glucometers which requires a sample of up to 12 microliters of blood. Which pipetman could you use to measure this amount? 12 microliters will fit in any pipet, but the P20 will give you the most accurate measurement
P20
P200
P1000
rat on a cupcakeDiabetic rats produce approximately 0.443 milliliters of saliva per half hour. If you wanted to measure out this amount in a pipetman, which one should you choose? careful!! 0.443 milliliters is 443 microliters... which has to go in the P1000


Answers:
P200, P1000, P20, P1000