Common mistakes in pipette operation

Pipette operation (a) common mistakes

I used to write "pipette operation" when I wrote "pipette selection" on the Internet, and I was fortunate enough to have been quoted several times. Of course, there are more than one person on the Internet who has written similar stuff. But do users value this issue very much? Unfortunately, the answer is no. A considerable number of people think that pipettes are very simple instruments, and their operation is very simple. There is no need to talk about it, and there is no need for any training courses. In fact? Good pipette handling habits can be beneficial for extending the life of the pipette, improving the accuracy of pipetting and maintaining the health of the user. The following may be to build some common operating habits in the laboratory, but also a more serious operating habits. I hope you don't find your own shadow in it.

First, install the tip. In laboratories where the pipettes are used frequently, the sound of tapping the tip is often heard one after another, adding a bit of music to the boring lab life. When you look into it, the user is afraid that the tip can't be tightened. After the tip is attached to the pipette, tap it again in the tip box several times. It is hoped that the impact can be used to ensure the pipetting seal. Sex. Where is this operation wrong? First, under the action of the impact, the tip may deform and affect the precision of pipetting. Second, the part of the pipette sleeve that contacts the tip undergoes multiple strong frictions, which gradually becomes rough and it is difficult to ensure the sealing. In order to achieve a good seal, a greater impact force is required, and a vicious circle begins. Third, the handle of a small-range pipette is relatively thin, and it is likely to become fishing under the continual impact of the impact. Hook; Fourth, sometimes the impact force is greater than the force that the pipette falls on the ground, and some of the precision parts in the pipette are overwhelmed and strike at any time.

Second, the angle of absorption. In order to facilitate the observation of the condition of the sample in the tip during the pipetting process, many users will keep the pipette at an angle of 45o or even closer to the horizontal angle during the pipetting process. But this is wrong again. First, when removing a sample that approaches or reaches the maximum volume of the tip, the tilting of the pipette at a large angle can easily cause the liquid to slip into the shank of the pipette, thereby contaminating or even corroding the piston of the pipette. It is easy to cause cross-contamination of the sample; secondly, the large angle of the pipette also increases the contact surface of the outer wall of the tip with the liquid, so that the liquid remaining on the outer wall is more when the tip leaves the liquid surface, and it is easy to When the liquid is drained, the liquid is removed from the tip together with the liquid in the tip, thereby reducing the precision of the pipetting. For the pipettes of the small range (such as 2 ul and 10 ul), the damage to the precision is likely to be deadly!

Third, the rate of liquid absorption. It is often seen in the laboratory that in order to "improve efficiency", the user quickly releases the thumb during aspiration, which causes the liquid to quickly rush into the tip. As everyone knows, this forces the liquid to form a turbulent state after entering the tip, so that for small and medium-range pipettes, a vapor mist that is invisible to the naked eye will enter the inside of the pipette, for a large-scale pipette. You will see the liquid flush directly into the inside of the pipette. The end result is contamination or even corrosion of the piston of the pipette, which is prone to cross-contamination of the sample and has an impact on accuracy.

Fourth, store. A considerable number of users will put the pipette directly on the test bench after the pipette is used. If it is neat, the pipette may be placed in the drawer. This is actually not good! During the pipetting operation, it is inevitable that liquid will enter the inside of the pipette. In the flat state, these liquids will remain on the piston and other components, and after a long period of time, the piston will pollute the piston and even corrode the piston.

Among the problems listed above, the case of corroding the piston is often mentioned. Someone might say: The piston of the pipette I use is corrosion resistant! But I still have to remind two points: First, except for a few low-end pipettes that use all-plastic parts, most pipettes have metal parts in their piston assemblies; second, as long as they pollute the piston, Regardless of the material of the piston, there may be problems with reduced internal airtightness of the pipette and cross-contamination of the sample.

In summary, it is necessary for laboratories to establish and improve the SOP (Standard Operating Procedures) used for pipettes and the management of strict pipette operations.

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