What precautions should be taken when using a pipette?

Pipette: Pipettes come in sizes 5, 10, 25, 50, and 75. A straight glass tube with a scale is usually referred to as a suction tube. The commonly used suction tubes have specifications such as 1, 2, 5, and 10mL. The volume transferred by pipettes and pipettes can usually be accurate to 0.01mL.

1. Usage: When using a disposable suction pipette, first check the pipette marking, accuracy, scale position, etc. Before use, wet the oil stains on the inner wall of the pipette with chromic acid solution. Then rinse the remaining detergent with tap water and rinse with distilled water. After cleaning, there should be no water droplets hanging on the inner wall of the pipette. Take the solution, use filter paper to absorb the moisture inside and outside the end of the pipette, and then rinse the tube wall 2-3 times with the solution to be taken, keeping the concentration of the solution unchanged.

2. Aspiration: Hold the upper end of the pipette with your right thumb and middle finger, and insert the lower opening of the pipette into the liquid to be aspirated. Insertion should not be too shallow or too deep, usually 10-20mm. If it is too shallow, it may cause air suction. Inhale the solution into the ear wash bulb and dirty it. If it is too deep, too much solution will stick to the outside of the tube. Grasp the ear wash ball with your left hand, first empty the ear wash ball, then connect the tip of the ball to the upper opening of the pipette, slowly release the flattened ear wash ball, and suck the solution into the tube. First, suck about 1/3, press the tube mouth with your right index finger, remove it, hold it horizontally, and rotate the tube to make the solution contact the upper part of the scale to replace the water in the tube. Inner wall, then discharge and discard the solution from the lower outlet of the tube. After washing repeatedly for 3 times, the solution above the scale can be absorbed. Immediately press the pipe mouth with your right index finger.

3. Adjust the liquid level: Lift the disposable suction pipette up from the liquid level height, with the end of the pipette still resting on the inner wall of the solution container, keeping the tube upright. Release the index finger slightly (sometimes gently rotate the pipette) to allow the solution in the tube to slowly flow out from the lower port until the bottom of the solution meniscus is tangent to the marked line. Immediately press the tube mouth with the index finger. Take out the droplet leaning against the wall, remove it from the pipette, and then insert it into the container receiving the solution.

4. Liquid release: If the container for holding the solution is a conical flask, tilt the flask at a 30 ° angle, keep the pipette vertical, and place the lower end of the pipette tightly against the inner wall of the conical flask. Release your index finger slightly to allow the solution to slowly flow down the wall of the flask. After all the solution has flowed out, take out the pipette 15 seconds later to allow the portion of the solution attached to the tube wall to flow out. If the pipette is not labeled with the word "blow", the residual solution in the pipette cannot be blown out because it is not included in the calibration volume of the pipette.

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