What is the correct way to use a pipette?

A pipette is actually a measuring instrument, which is mainly used to measure the volume of a solution. It is easy and simple to use, and the measurement effect is relatively accurate. However, you should also pay attention to the method of using the pipette. Only the correct method can achieve better results. The following is a detailed introduction on how to use the pipette correctly and the issues that need attention.

1. Usage steps

Select a pipette of appropriate specifications according to the volume and requirements of the solution to be transferred. A pipette is generally used to accurately transfer solutions in titration analysis, and a pipette is generally used when the reaction requires controlling the amount of test solution added.

2. Check the instrument

Check the pipette's mouth and tip for damage. If damaged, do not use it.

3. Clean the instrument

First rinse with tap water and then soak it in chromic acid cleaning solution. The operation method is as follows: hold the pipette or pipette at an appropriate position on the upper end with your right hand, with your index finger close to the upper end of the tube, the middle finger and ring finger open to hold the outside of the pipette, the thumb is held on the inside of the pipette between the middle finger and ring finger, and the little finger is naturally relaxed; hold the ear wash bulb with your left hand, hold it in a fist, hold the ear suction ball in the palm of your hand, with the tip facing down, hold the ear suction ball tightly, expel the air in the ball, insert the tip of the ear suction ball into or close to the upper end of the pipette (pipette), and be careful not to leak. Slowly release the fingers of your left hand and slowly suck the washing solution into the tube until it reaches the part above the scale line. Remove the ear suction bulb and quickly block the upper opening of the pipette (pipette) with your right index finger. After waiting for a while, put the washing solution back into the original bottle. Rinse the inner and outer walls of the pipette with tap water until no water droplets remain, then wash with distilled water three times, drain and set aside.

4. Absorb the solution

Shake the solution to be absorbed evenly, pour a small portion of the solution to be absorbed into a clean and dry small beaker, use filter paper to absorb the moisture inside and outside the tip of the cleaned pipette, and insert it into the small beaker to absorb the solution. When the pipette capacity is 1/3, immediately press the tube mouth with the index finger of your right hand, take it out, hold it horizontally and rotate the pipette to make the solution flow through the inner wall of the tube, and discharge the solution from the lower tip into the waste liquid cup. Repeat this process 3-4 times before absorbing the solution.

5. Adjust the liquid level

Take another clean small beaker in your left hand, place the tip of the pipette close to the inner wall of the small beaker, keep the small beaker tilted, keep the pipette vertical, and keep the scale line and line of sight horizontal (the left hand cannot touch the pipette). Slightly loosen your index finger (you can slightly rotate the pipette or suction tube) to allow the solution in the tube to slowly flow out from the lower opening. When the liquid level is about to reach the scale line, press your right index finger tightly, pause for a moment, and then follow the above method to lower the bottom line of the meniscus of the solution until it is tangent to the upper edge of the mark line. Immediately press the tube mouth with your index finger. Place the tip close to the inner wall of the beaker and move it slightly toward the mouth of the beaker to remove any droplets from the tip. Carefully transfer the pipette or pipette into the container containing the solution.