Hawach pipette is a meter-out instrument used only to measure the volume of the solution it emits. It is a slender glass tube with a large bulk in the middle. Its lower end is sharp-pointed, and a marking line is engraved at the neck of the upper end, which is a sign of the exact volume removed. Commonly used pipettes are available in 5, 10, 25, and 50 mL sizes. Straight glass tubes with graduations are often called pipettes. Commonly used pipettes are available in sizes of 1, 2, 5, and 10 mL. Pipettes and pipettes are usually accurate to 0.01mL.
1. Before use: When using a pipette, you must first look at the pipette mark, accuracy level, scale position, etc. Before using the pipette, rinse it with chromic acid washing solution to remove the oil on the inner wall of the pipe. Then rinse the remaining lotion with tap water and rinse with distilled water. After cleaning, the inner wall of the pipette should be free of water droplets. Before removing the solution, the water inside and outside the pipette end should be dried with filter paper, and then the tube wall should be washed with the solution to be removed 2 to 3 times to ensure that the concentration of the removed solution does not change.
2. Aspiration: use the thumb and middle finger of the right hand to pinch the upper end of the pipette, insert the lower mouth of the pipe into the solution to be absorbed, and insert it not too shallow or too deep, generally 10 ~ 20mm, too shallow will produce Suction, suck the solution into the ear wash ball to stain the solution, too deep and the solution will stick to the outside of the tube too much. Take the ear wash ball with your left hand, first press out the air in the ball, and then connect the tip of the ball to the top of the pipette.
Slowly loosen the flat ear wash ball to draw the solution into the tube. / 3 or so, hold the nozzle with the index finger of your right hand, take it out, hold it horizontally, and turn the tube to make the solution contact the part above the scale to replace the water on the inner wall, then release the solution from the lower mouth of the tube and discard it. After repeated washing 3 times, you can draw the solution above the scale, and immediately press the nozzle with the index finger of your right hand.
3. Adjust the liquid level: lift the pipette up and away from the liquid level, the end of the tube still rests on the inner wall of the solution container, the tube body stays upright, slightly relax the index finger (sometimes you can slightly rotate the straw) to make the solution in the tube slowly The lower mouth flows out until the bottom of the meniscus of the solution is tangent to the marked line, and immediately press the nozzle with the index finger. Remove the tip droplets against the wall, remove the pipette, and insert it into the container holding the solution.
4. Discharge the solution: If the container receiving the solution is a conical flask, the conical flask should be tilted 30 °, the pipette should be upright, and the lower end of the tube should be close to the inner wall of the conical flask. Release the index finger slightly, and let the solution slowly flow down the bottle wall. After waiting for 15 seconds for the entire solution to flow out, take out the pipette so that part of the solution attached to the tube wall can flow out. If the pipette is not marked with “blow”, the solution remaining in the tip of the pipette cannot be blown out, because this part of the residual solution is not included in the calibrated volume of the pipette.
1. After the pipette raises the liquid surface, apply filter paper to wipe off the liquid that is attached to the outer wall of the pipette;
2. When looking at the scale, the scale of the pipette should be parallel to the eye, and the bottom meniscus shall prevail.
Correct use of pipette, blow, or not.
Pipettes and graduated pipettes are necessary glass instruments commonly used in laboratories. The operation has the doubts of “blowing” and “no blowing”. The query data is arranged as follows:
Pipettes and graduated pipettes are generally marked with: “Fast”, “A”, “B”, “Blow” four symbols, write “Fast” or “B”: you see that the liquid is finished, wait for three In seconds, the amount of liquid transferred reaches the indicated volume of liquid. The opposite of “quick” is the tube that says “A”: this kind of tube is generally very expensive and more accurate.
After seeing the liquid transfer, you need to wait another 15 seconds for the pipette to leave. Container wall. The word “blowing” means: after the end of the discharge, the remaining liquid column at the tip of the pipette needs to be blown into the container with an ear wash ball before it is considered to reach the target volume. This liquid column can generally reach 0.1-0.3 ml, which is still a large amount. You must pay attention to it, otherwise, the volume error will be too great. There are very few “A” pipes with “blowing”-generally “B” or “fast” pipes with “blowing”.