Question

Exercise 3: Using a Micropipette:

1. Which type of pipette (P10, P20, P100, P200, OR P1000) would you use to aliquot the following volumes? Use the range information on page 19 of your lab manual (Table 2.3) to complete the table. Choose one type of pipette for each amount (types of pipettes may be repeated among the volumes).

Volume	Type of Pipette
150 mL
999 mL
2 mL
10 mL
68 mL

2. What is the difference between the first stop and the second stop when you press the pipette plunger down?

3. Why is it good laboratory practice to change tips when aliquoting different solutions?

Answer 1

I think the ml which is written after each volume is wrong. it should be microlitre (µl).

Volume	Type of Pipette
150 µl	P200
999 µl	P1000
2 µl	P10
10 µl	P20
68 µl	P100

Lower limit of P200 is 50 µl and upper limit is 200µl. So 150 µl can be measured.

Lower limit of P1000 is 200 µl and upper limit is 1000µl. So 999 µl can be measured.

Lower limit of P10 is 1 µl and upper limit is 10µl. So 2 µl can be measured.

Lower limit of P20 is 2 µl and upper limit is 20µl. So 10 µl can be measured.

Lower limit of P100 is 10 µl and upper limit is 100µl. So 68 µl can be measured.

When a pipette is reached the first stop, it means the amount which has been set at the pipette is released. If we want to release all the remaining liquid in the tip, then a second push is needed and then the pipette is moved to the second stop.

It is a very good practice to change tip at everytime during aliquoting . It reduces the chance of mixing between the various chemicals we used for aliquoting. If we work with microbes, it reduces the chance of contamination. So, for reducing chance of any mixing of contamination or mixing, fresh tip use is mandatory.