The 0 th lab: An exercise in pipetting. This exercise will consist of a video demonstration on proper pipetting technique followed by an exercise for you to practice your precision. The following text reviews many of the points mentioned in the video and is for your review after this session and later in the term. Pipettes and Pipetting Few analytical techniques are as important as the transfer of liquids. Some type of pipette will almost always be used and the development of an accurate, consistent, pipetting technique is essential to all biochemistry students. The mechanical pipettor is generally used for routine and repetitive pipetting in the laboratory. There are several brands on the market of various shapes and sizes, but they all work in a similar fashion: a disposable plastic tip is mounted over the end of the pipette which acts as an adjustable plunger. (Tips are colour coded to match the correct size to each size pipette). The procedure shown in Figure 1.2 is then followed (reprinted from the Gilson guide to pipetting). Hold the instrument in a nearly vertical position. Depress the plunger smoothly to the first stop position. Rest 1 2 75 Res 1 2 Immerse the end of the pipette 2 tip in the liquid". Allow the plunger to move up smoothly to the rest position. Wait one second if using an air displacement pipet- ter (not necessary for positive displacement). Place the pipette tip at an angle 3 (10 to 45%) against the inside wall of the receiving vessel. Depress the plunger smoothly to the first stop position. Figure 1. Use of the Gilson pipette. Wait one second, then depress 4 the plunger to the second stop position. This "blow-out" stroke removes any remaining sample from the tip. Remove pipette by sliding the tip up the sidewall of the reci- pient. Allow the plunger to move up to the rest position. Mechanical pipetters may either deliver fixed standard volumes (e.g., 10 uL, 20 uL, 50 uL, etc.) or may be adjustable over a narrow range. The fixed volume type are generally more accurate. The accuracy and reproducibility of a given model of pipette is given in the literature supplied with the pipette, but the values given are for a well maintained pipette used precisely.
BCHM 317 - The Oth lab 2 P2 0.2 - 2 uL Clear tip P20 2 - 20 UL Yellow tip P200 20 -200 uL Yellow tip P1000 100 - 1000 uL Blue tip For maximum accuracy with all types of pipette, the pipette and tip are matched to the desired volume (e.g. use a P200 rather than a P1000 to deliver a 100 uL sample). You should not use a pipette outside of its specified range as it will be either inaccurate, cause damage to the pipette or both. When pipetting, special attention should be paid to smooth controlled loading, uniform timing and motion. Do not snap the plunger when loading. Below are some general guidelines on the use of