Pipette tip | Guide to the correct use of laboratory pipettes
Pipettes are indispensable in the laboratory,
But there will inevitably be mistakes in repeated operations.
So an excellent experimenter
It all starts with the correct use of the pipette.
We together look!
1. Factors affecting the accuracy of the pipette gun
(1) Temperature: When the room temperature is low, the hand temperature is high, which causes the air to expand, and errors often occur when inhaling cold solution
(2) Air tightness: the joint between the tip and the gun body, and the long-term wear and tear between the inner cylinder of the gun, cause errors
(3) Suction speed: It is easy to cause bubbles in the tip and contaminate the tip
(4) The volatilization of the reagent: when the reagent with high volatility is sucked, the steam enters the tip of the gun, and the internal pressure increases. As a result, the pressure increases when the liquid is pressed out, which causes errors. Solution: It can be improved by repeated pumping 4-5 times.
2. Specific usage method
Replace tip method: the most accurate.
(1) Adjust the knob to the required scale position. The trick: first slightly exceed it, and then turn it back to the scale. Note that it is forbidden to exceed the maximum scale to avoid human error.
(2) Insert the tip: When performing aseptic operation, pay attention to the rapid and correct action. Do not touch the tip with your hands. The strength of the action must be consistent, and waste action should be prohibited. In normal operation, you can use your thumb and index finger to tighten, but your hand cannot touch the tip of the tip.
(3) Finger pressure to the first segment, the tip of the tip touches the reagent. The white tip is 1mm into the liquid surface, the yellow tip is 2-3mm, and the blue tip is 2-4mm to avoid errors caused by the influence of hydraulic pressure.
(4) Slowly suck the reagent, and prohibit the liquid from entering the pipette tip if the speed is too fast.
(5) After removing the tip, lightly lean on the inner wall of the container to make the liquid flow down from the outer wall of the tip.
(6) Stick the tip on the inner wall of the target container, and gently press it to the first section to press out the liquid.
(7) The tip of the tip slides slightly on the inner wall of the container, leaving a small amount of liquid on the tip, remove the target container, remove the tip with your fingers, and be careful not to spill the reagent.
One tip dispensing method: Not suitable for volatile and toxic reagents.
(1) Same as A-D above, after removing the liquid surface, first slowly press to the first section, and then firmly press to the second section to fully press out the reagent.
(2) Same as C above, suck out the liquid slowly.
(3) In the air above the target container, press the reagent to the second stage, pay attention to the pressure to be the same as A, and pay attention to the reagent not to splash around.
(4) Slowly return to the first stage and repeat the above operation. Achieve the goal that the original liquid of the target container does not pollute the tip.
How to transfer several ul of precious reagents:
(1) Same as A-D above, after removing the liquid surface, press a few times on the inner wall of the container to make the outer wall liquid flow down. The most important thing is that the white tip enters 1mm below the liquid level.
(2) The tip of the tip is immersed under the liquid surface of the target container and slowly pressed to the first section.
(3) Loosen, return to the first stage, re-inhale the liquid, repeat 4-5 times, and wash the liquid on the inner wall of the tip.
(4) Remove the tip of the tip from the liquid surface, gently press the inner wall, and press out the liquid to the second section.
1. Install Filter Pipette Tip
Push down the pipette handle firmly and rotate it slightly when needed.
Wrong operation: hit the tip hard. This method will cause damage to the tip and even wear of the pipette sleeve handle, which will affect its tightness.
2. Range setting
Please select the correct pipette before operation. The pipette can be operated in the range of 10-100% of the range, but operation at 10% of the range requires high pipetting skills, so it is recommended to operate in the range of 35-100%. .
Range adjustment: When adjusting from a small range to a large range, rotate continuously in the direction of the required range, and then return to the required range when the rotation reaches 1/3 of the required range. When adjusting from a large range to a small range, it rotates directly and continuously to the required range.
3. Rinse
Repeat aspiration and drainage with the same sample two to three times, and rinse to provide the same contact surface for each subsequent aspiration to ensure the consistency of operation.
Note: Please do not rinse with high temperature or low temperature liquid!
4. The immersion angle of the tip
When aspirating liquid, try to keep it upright, and the inclination angle should not exceed 20°.
5. The immersion depth of the tip
6. Tip immersion time
After aspirating the liquid, keep it in the liquid surface for one second and then gently remove the tip. This is especially important for large-volume pipettes or when aspirating viscous samples.
7. Suction speed
Pipette at a constant speed and control the pipetting speed. Too fast will cause spray, liquid or aerosol to rush into the pipette and contaminate the piston and other parts.
8. Draining and blowing liquid
First press the piston to the first gear to discharge the liquid, after a short pause, press to the second gear to blow the liquid.
9. Hand temperature
The pipette should not be held in your hand for a long time. It is best to hang it on a stand or hang it on your hand to dry when not in use.
Pipette error operation and treatment method As the most commonly used manual adjustable precision pipette in liquid operation, some wrong operations during use will bring errors to the operation itself, and some will cause damage to the machine, etc., here A brief summary is as follows:
Error: When assembling the Pipette Tip, repeatedly hit the tip with a pipette.
Correct: Insert the suction head, turn left and right slightly to tighten the suction head
Analysis: The impact will cause the internal gear combination of the pipette to loosen, and long-term operation will affect the accuracy of the pipette.
Error: The tip does not match the pipette, which affects the air tightness. Correct: Use the tip that matches the pipette and has quality assurance.
Analysis: The mismatch of the tip is mainly manifested in the impact on air tightness. Will directly affect the accuracy of the pipette, usually the pipetting operation will be less than the set volume.
Error: When aspirating liquid, the pipette tilts to aspirate liquid
Correct: vertical aspiration
Analysis: The inclined state will cause the change of the air pressure surface. Will affect the accuracy of pipetting.
Error: When the tip contains undisputed liquid, the pipette is placed flat on the table
Correct: Hang the pipette vertically on the pipette holder
Analysis: The tip contains undisputed liquid. After the pipette is placed flat, the liquid may flow into the pipette body, which will affect the internal components of the pipette, causing serious damage, poor pollution, etc. happened.
Error: Use a large pipette to pipette small volumes of liquid
Correct: The pipetting volume must be within the range provided by the pipette to meet the requirements of inaccuracy and inaccuracy
Analysis: Because of the existence of the air cushion, it is the main reason for the inaccuracy of the pipette. The selection of the pipette should be the largest range, which is closest to the selection principle of the target liquid transfer volume.
Mistake: aspirate liquid with strong volatility
Correct: It is not recommended to use ordinary pipettes for strong volatile liquid transfer
Analysis: If you must pipette highly volatile liquids, you should disassemble the pipette immediately after pipetting to allow the vapor to evaporate. At the same time, it is recommended to use an external piston pipette.
Error: aspiration speed and dispensing speed are too fast
Correct: Slow in and slow out
Analysis: Quick aspiration for pipettes with a volume of 1 mL and above, it is easy to cause liquid to flush. Dispensing too quickly will increase the amount of liquid remaining.
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