Pipetting operation method of pipette gun

The pipette gun is a common tool used by every inspector. Many people ignore the correct use of the pipette gun and some detailed operations. Now it will be described in detail in several aspects.

1. Use of pipette gun

01 Adjustment of measuring range

When adjusting the range, use your thumb and index finger to rotate the knob on the upper part of the liquid dispenser. If you want to adjust the volume from large to small, follow the normal adjustment method and just turn the knob counterclockwise; but if you want to adjust the volume from small to large, When measuring, you can first turn the scale knob clockwise to a scale that exceeds the measurement range, and then adjust it back to the set volume. This can ensure the highest accuracy of measurement. During this process, never turn the button out of the range, otherwise it will jam the internal mechanism and damage the pipette.

02 Assembly of the gun head

When putting the pipette tips on the pipette gun, many people will knock the pipette tip box hard several times, which is wrong because it will cause the internal accessories of the pipette gun (such as springs) to be damaged. It becomes loose due to the instantaneous impact force generated by knocking, and even causes the scale adjustment knob to get stuck. The correct method is to insert the pipette (device) vertically into the pipette head and turn it left and right with a little force to make it tightly connected.

03 Pipetting method

Before pipetting, make sure the pipette, tip, and liquid are at the same temperature. When absorbing liquid, hold the upper part of the pipette with four fingers together, press the button on the top of the plunger rod with your thumb, keep the pipette in an upright position, insert the tip of the pipette 2-3 mm below the liquid surface, and slowly release the button. Aspirate the liquid and stay for 1 to 2 seconds (the residence time can be longer for solutions with high viscosity). Slide the suction head out of the container along the wall. When draining the liquid, the suction head contacts the inclined wall. Before aspirating, you can suck up the liquid several times to moisten the suction nozzle (especially when you want to suck up liquids that are viscous or have a density different from water). Finally, press the suction head removal push rod to push the suction head into the waste tank.

04 Two pipetting methods

1. The first is the forward pipetting method. Use your thumb to press the button to the first stopping point, then slowly release the button to return to the original point. Then press the button to the first stop point to discharge the liquid, pause for a moment and continue to press the button to the second stop point to blow out the remaining liquid. Finally release the button.

2. The second is the reverse pipetting method. This method is generally used to transfer highly viscous liquids, biologically active liquids, easily foaming liquids, or extremely small amounts of liquid. The principle is to first inhale more liquid than the set range, and there is no need to blow out the remaining liquid when transferring the liquid. First press the button to the second stopping point, then slowly release the button to the original point. Then press the button to the first stop point to discharge the liquid with the set range. Continue to hold the button at the first stop point (do not press it down again). Remove the pipe tip with residual liquid and discard it.

2. Maintenance of pipette gun

If it is not in use, you need to adjust the pipetting gun range to the maximum scale, keep the spring in a relaxed state, protect the spring, and hang it vertically on the pipetting gun holder.

After daily use, the outside of the pipette should be cleaned with 10% sodium hypochlorite or 70% alcohol and then dried naturally. Pay special attention to the cone of the pipette nozzle so that no solution (blood) remains.

Pipettes must be calibrated regularly as required.

3. Precautions for using pipettes

1. When absorbing liquid, be sure to release your thumb slowly and steadily, and never release it suddenly to prevent the solution from being absorbed too quickly and rushing into the pipette to corrode the plunger and cause air leakage.

2. In order to obtain higher accuracy, the tip needs to absorb the sample solution once before formally pipetting, because when absorbing serum protein solution or organic solvent, a "liquid film" will remain on the inner wall of the tip, resulting in a large amount of liquid discharge. Too small to produce errors.

3. It is very undesirable to tighten the pipette by repeatedly hitting the tip. Long-term operation will loosen the internal parts and damage the pipette.

4. Do not pipette when the pipette is not equipped with a suction tip.

5. The pipette is strictly prohibited from absorbing highly volatile and corrosive liquids (such as concentrated acid, concentrated alkali, organic matter, etc.).

6. It is strictly prohibited to use a pipette to mix the liquid.

7. Do not use a large-capacity pipette to transfer small volumes of liquid to avoid affecting accuracy. At the same time, if you need to transfer a larger amount of liquid outside the measuring range, please use a pipette.

8. Check whether there is any leakage when using.

Method: After absorbing the liquid, place it vertically in the air for a few seconds to see if the liquid level drops.

If there is leakage, the reasons may be as follows:

1. Whether the gun head matches;

2. Is the spring piston normal?

3. If it is a volatile liquid (as is the case with many organic solvents), it may be a problem of saturated vapor pressure. You can aspirate the liquid several times before pipetting.