How to use a pipette

When conducting research on analysis and testing, a pipette is generally used to measure a small amount or a small amount of liquid.  Many people will ignore the correct use of the pipette and some details of its operation.  Now it will be described in detail in several aspects.

Range adjustment

When adjusting the range, if you want to adjust from a large volume to a small volume, you can rotate the knob counterclockwise according to the normal adjustment method;  but if you want to adjust from a small volume to a large volume, you can first turn the dial knob clockwise to exceed The scale of the range, and then call back to the set volume, so as to ensure the highest accuracy of the measurement.  During this process, never push the button out of the range, otherwise, it will jam the internal mechanical device and damage the pipette.

Assembly of the pipette tip (suction nozzle)

When putting the pipette tips on the pipette gun, many people will knock on the pipette box a few times, which is the wrong way, because it will cause the internal accessories of the pipette gun (such as springs).  The instantaneous impact force produced by the knocking becomes loose and may even cause the scale adjustment knob to become stuck.  The correct method is to insert the pipette (instrument) vertically into the tip of the pipette and turn it slightly tightly with a little force to make it tightly combined.  If it is a multi-channel (such as 8 or 12) pipette gun, you can align the first pipette with the first pipette tip, and then insert it obliquely, shake it forward and backward to lock it.  The sign that the gun head is clamped is slightly over the O-ring, and you can see that the connection part forms a clear seal ring.

Pipetting method

Before pipetting, make sure that the pipette, tip, and liquid are at the same temperature.  When aspirating the liquid, keep the pipette upright and insert the tip of the pipette 2-3 mm below the liquid surface.  Before sucking liquid, you can suck the liquid several times to wet the suction nozzle (especially when you want to suck a viscous liquid or a liquid with a different density).  At this time, two pipetting methods can be used.

One is the forward pipetting method.  Use your thumb to press the button to the first stop, and then slowly release the button to return to the original point.  Then press the button to the first stop point to discharge the liquid, and after a while, continue to press the button to the second stop point to blow out the remaining liquid.  Finally, release the button.

The second is the reverse pipetting method.  This method is generally used to transfer high-viscosity liquids, biologically active liquids, easy-foaming liquids, or very small amounts of liquids.  The principle is to inhale more than the set range of liquid first, and not need to blow out residual liquid when transferring liquid.  First, press the button to the second stop, and slowly release the button to the origin.  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 down again), remove the tip of the residual liquid, and discard it.

Correct placement of the pipette

After use, you can hang it vertically on the pipette holder, but be careful not to drop it.  When there is liquid in the pipette tip, do not place the pipette horizontally or upside down to prevent the backflow of liquid from corroding the piston spring.

Precautions during maintenance

1 If not in use, adjust the range of the pipette to the maximum scale to keep the spring in a relaxed state to protect the spring.

2 It is best to clean the pipette regularly, you can use soapy water or 60% isopropyl alcohol, then use distilled water to clean, and dry naturally.

3 Before high-temperature disinfection, make sure that the pipette can adapt to the high temperature.

4 Calibration can be carried out by repeating the weighing of distilled water several times in a 20-25 degree environment.

5 Check if there is any liquid leakage during use.  In this method, after absorbing the liquid, hang it vertically and let it stand for a few seconds to see if the liquid level drops.

6 If the liquid leaks, the reasons are rough as follows:

1) Whether the gun head matches;

2) Whether the spring piston is 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.  The liquid can be aspirated several times before pipetting.