Three Skills When Using Pipette
A pipette is an indispensable tool for the experimental operation in the laboratory. It is important to reduce the experimental error to the minimum and improve the repeatability to best.
Factors Affecting The Accuracy
The first thing should be noticed is the accuracy of the pipette during the experimental process. There are mainly three factors that would affect its accuracy in varying degrees. The first common factor is temperature. The air will be expanded when its temperature is higher than the room temperature, which would cause the occurrence of the error when inhaling the cold solution.
The second factor is airtightness, which is caused by the long-term wear of the internal cylinders and the joint between the tip and the pipette body.
The third factor is the volatilization of reagent. When drawing the high-volatility reagent to the pipette, the steam will enter the tip and the internal pressure will be increased.
Consequently, the pressure will be higher when the sample is pressed out, which causes an error to occur. The error could be reduced by repeatedly pumping the pipette 4-5 times.
Specific Operation Sequence
There are mainly six steps to use the pipette, which includes loading the tip by pressing it down on the handle; setting the range within a recommended range of 35-100%; rinsing the tip by repeating the pipette 2-3 times with the same sample; drawing the liquid in a vertical angle or inclined less than 20℃ with a continuous speed: draining and blowing the reagent and finally removing the pipette tip.
Now we will introduce three skills when using pipette based on the correct operation.
The first skill is filling the suction head correctly. When the recommended range of a suction head is from 10% to 100% of the maximum suction capacity, the highest accuracy can be achieved within the small and optimized range of 35% to 100%. Within such a small range, the requirement for operator skills will be lower and the accuracy of results will be improved by about 1%. And the best results can be obtained when it is filled with 50% of nominal capacity.
The second skill is keeping the vertical water entry angle while inhaling fluid. Make the inflow angle as close as possible to the vertical position, otherwise, too many samples will be inhaled. And this operation skill can improve pipette accuracy by 2%. When separating liquid, the suction head should keep a small angle with the container wall to ensure a good drainage effect.
The third skill is the proper intake depth of the suction head. If the suction head is sucked too deep into the water, the suction volume will increase with the increase of pressure. The liquid retained on the suction head surface will affect the results. If the suction head is not sucked deep into the water, air will enter the suction head, which results in bubbles and inaccurate capacity. And the correct depth of water inflow can improve accuracy by 5%.