Buffers and Pipetting

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1.0 g/mL and 1.13 g/mL used respectively as density of water and 50% glycerol to calculate the expected weight.

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Figure 1 Average percentage difference for P200 water vs P200 50% Glycerol

As you can see in the figure 1, average percentage difference of P200 water and P200 glycerol using the 1st stop is lower than average percentage difference of P200 water and P200 glycerol using the 2nd stop.

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Figure 2 Average percentage difference of P20 water vs P20 50% glycerol

In figure 2, you can see that P20 water and P20 50% glycerol using the 2nd stop higher that P20 water and P20 50% glycerol as well.

Discussion

Using the micropipette properly is one of the essential skill in Biochemistry. We use the 1st stop to fill the micropipette tip and we only the 2nd stop to dispense the solution in the tip. However, in this experience the 1st stop and the 2nd stop was used to fill the micropipette tip. As expected, the average percentage difference was 45% when you are using the 2nd stop to draw a solution and the average percentage difference for micropipette using the 1st stop was 2.97% which indicates that pushing plunger to the 2nd stop causes inconclusive result further affecting the protein concentration and DNA calculations (See table 1).

It is known that accuracy of the micropipette decreases as you select the unnecessarily large pipette for small solution but when we’re using the P200 and P20, the result was different that what we expected. The average percentage difference for the P20 water using the 1st stop is 7.3 and 2.9 for the P200 water, its because water is one of the liquids that has a high surface tension which means that the intermolecular force holds the liquid together which decreases the specificity of the analysis.

In conclusion, in order to increase the accuracy is to use the micropipette properly by using the 1st stop to draw the liquid and 2nd stop to dispense the liquid from the tip. Also it is important the physical properties of the solution that we’re using in the experiment must be taken into account.

Works cited

- Koivisto, Sami. “The Tip of Perfection.” LaboratoryEquipmen.com, 31 July 2007