Selection and use of pipettes and introduction to maintenance

When conducting research on analysis and testing, a pipette is generally used to measure a small amount or a small amount of liquid.

1. Purchase of pipette (pipette):

1. Product performance, that is, the accuracy and repeatability of pipettes, for most users, it is difficult and unnecessary to check product performance before purchasing. Therefore, it is mainly based on the technical data provided by the manufacturer. However, here are two points to make clear: first, do n’t easily believe the seller ’s verbal commitment, and you must check the written materials provided by the manufacturer; second, the brands that have a greater impact on the global pipette market, such as SOCOREX, EPPENDORF And GILSON, etc., the technical data provided by it is more reliable.

2. The reliability and durability of the product depends mainly on the material used for the pipette. For the housing, it should have higher impact resistance, corrosion resistance and lower thermal conductivity (such as PVDF material); for the piston, there are mainly three materials on the market: stainless steel, ceramic and plastic. Stainless steel has good mechanical properties and long life, but it is not suitable for pipetting of strong acids and alkalis; ceramics have high corrosion resistance, but poor mechanical properties. Of course, high-quality materials often mean higher prices, so it is necessary to comprehensively consider the factors of purchase price and life.

3. The ergonomic design of the product can mainly consider the following points: first, the short moving distance of the thumb to complete a pipetting cycle means higher comfort; second, comparing a pipette with the same range to complete a liquid discharge (certain Press to the bottom) The required force of the thumb is the key to affecting comfort. The less force means the less risk of finger damage caused by long-term use; third, the loading and unloading of the suction head is also the less laborious the better; fourth, The weight of the pipette is moderate, too heavy will increase the burden on the hand, but too light also often means that the material may be unsatisfactory; fifth, other auxiliary designs, such as the matte design of the shell and the design of the finger hook, help to further improve Comfort. In terms of ergonomics, SOCOREX is in a leading position in the global pipette market, and has perfect performance in the above points.

Second, the adjustment of the use range of the pipette (pipette) When adjusting the range, if you want to adjust from a large volume to a small volume, according to the normal adjustment method, turn the knob counterclockwise; but if you want to adjust from a small volume If the volume is large, you can turn the scale knob clockwise to the scale beyond the range, and then return 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. The assembly of pipette tips (pipette tips) When putting pipette tips on a pipette gun, many people will forcefully tap on the pipette tip box a few times. This is the wrong approach because it will cause the pipette gun The internal accessories (such as springs) become loose due to the instantaneous impact force caused by the knocking, 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 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 do 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. After the pipette is properly placed and used, it can be hung 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 for maintenance of pipettes (pipettes) 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. It is best to clean the pipette regularly. You can use soapy water or 60% isopropyl alcohol, then use distilled water to clean, and let it dry naturally. Before high temperature disinfection, make sure that the pipette can adapt to high temperature. Calibration can be carried out in a 20-25 degree environment by repeating the method of weighing distilled water several times. When using it, check for liquid leakage. In the method, after absorbing the liquid, hang it vertically and let it stand for a few seconds to see if the liquid level drops. If there is liquid leakage, the reasons are roughly as follows: 1. Whether the gun head is matched; 2. Whether the spring piston is normal; 3. If it is a volatile liquid (as many organic solvents are), it may be a problem of saturated vapor pressure. The liquid can be aspirated several times before pipetting.