Many people who use pipettes for the first time think that the operation of pipettes is very simple, but it is not. The operation of the pipette is the first step in a scientific experiment. It is a very basic experimental operation, but most people have a prejudice against the operation of the pipette. In fact, there are a lot of knowledge about pipette operation.
May ask yourself these few questions, you can see if your operation is biased:
The piston realizes liquid suction and discharge through the expansion and contraction movement of the spring.
2 Adding sample volume range:
It is not suitable for pipetting high-viscosity liquids and liquids with high volatility easily cross-contamination. Wrong usage habits can easily lead to inaccurate pipette accuracy and even internal corrosion of the pipette, etc.
A complete pipetting cycle:
3.1. Pipette Tip installation
The correct installation method is called the rotary installation method
Insert the tip of the pipette into the pipette tip (no matter whether it is a bulk pipette tip [tip loader - for automatically refill the bulk pipette tips into empty rack] or a boxed pipette tip), while pressing down gently and firmly, turn it left and right slightly to tighten.
3.2. Pipetting volume setting
Coarse adjustment: Use the rotary button to quickly adjust the volume value to close to your expected value;
Fine adjustment: When the volume value is close to your expected value, you should place the pipette horizontally in front of your eyes, and slowly adjust the volume value to the expected value through the adjustment wheel to avoid the impact of visual errors ;
Pipetting volume setting
When adjusting from a large volume to a small volume, it is the normal adjustment method, and it is just fine to adjust;
When adjusting from a small volume to a large volume, it is necessary to first adjust the scale that exceeds the set volume, and then return to the set volume to ensure the best accuracy. (This is because there is a certain gap in the counter, which needs to be filled).
3.3. Pre-washing the gun head
After we install a new pipette tip or increase the capacity value, we should absorb and discharge the liquid that needs to be transferred two to three times. This is to form a homogeneous liquid film on the inner wall of the pipette tip to ensure the accuracy and precision of the pipetting work. Accuracy makes the entire pipetting process extremely reproducible.
When inhaling organic solvents or highly volatile liquids, volatile gases will form a negative pressure in the white sleeve chamber, resulting in liquid leakage. At this time, we need to pre-wash four to six times to make the gas in the white sleeve chamber saturated , The negative pressure will disappear automatically.
The viscous liquid can be accurately pipetted by pre-wetting the pipette tip. First aspirate the sample liquid, and then discharge it. The inner wall of the pipette tip will absorb a layer of liquid to make the surface adsorption saturated, and then suck the sample liquid, and finally discharge the liquid. The volume will be very precise.
First press the pipette discharge button to the first stop point, and then immerse the pipette tip vertically into the liquid surface. The immersion depth is:
P2, P10 ≤ 1 mm;
P20, P100, P200 ≤ 2 mm;
P1000 ≤ 3 mm;
P5mL, P10mL ≤ 4 mm;
If the immersion is too deep, the hydraulic pressure will have a certain impact on the accuracy of liquid suction. Of course, the specific immersion depth should be flexibly controlled according to the size of the liquid container.
When discharging, the tip of the pipette is close to the container wall, first press the discharge button to the first stop point, and after a slight pause, press to the second stop point. This will ensure that there is no residual liquid in the pipette tip. If there is residual liquid after this operation, the tip should be replaced.
When inhaling liquid during operation, press the button to the first level to absorb liquid and release the button. When discharging liquid, first press the first level to discharge most of the liquid, and then press the second level to discharge the remaining liquid.
When inhaling liquid, directly press the button to the second position and then release it, so that more liquid will be sucked in. When the liquid is discharged, just press the first position. The more sucked liquid can compensate for the surface adsorption inside the pipette tip. The reverse sucking liquid is generally used in combination with the pre-wetting liquid sucking method, which is suitable for viscous liquids and volatile liquids.
3.6. Remove the gun head
The removed pipette tip must not be mixed with the new pipette tip to avoid cross-contamination.
After the pipette is used up, it is adjusted back to the maximum range.
Is the pipette leaking?
1. Visual inspection:
After sucking the liquid, let the pipette stand vertically for 15 seconds, and observe if there is any droplet flowing out slowly. If there is outflow, it means there is air leakage. (For P2, P10, P20, P100, P200 pipettes, please immerse the pipette tip 1-2 mm into the liquid surface and let it stand for 20 seconds to observe whether the liquid level inside the pipette tip drops. If it drops, it will be explained The pipette in your hand is leaking).
2. possible reasons:
Possible causes and measures
Cause: Tips do not match
Measure: Use the original matching tip
Cause: The tip is not tightened when assembling the gun
Measure: Pay attention to the method of assembling the tip
Cause: The internal air tightness of the pipette is not good
Measure: Ask the engineer of the instrument manufacturer to deal with it
Clean the micropipette in our hands regularly, just use alcohol cotton, mainly to wipe the shell, which can keep the appearance and reduce the possibility of contamination to the sample;
After absorbing the highly volatile and highly corrosive liquid, the entire pipette should be disassembled, the piston rod and the inner wall of the white sleeve should be rinsed with distilled water, and then installed and used after drying. In order to prevent the volatile gas from being adsorbed on the surface of the piston rod for a long time, corroding the piston rod and damaging the pipette.