A little tip about Laboratory Pipette
A pipette is a device used to quantitatively transfer liquids. When conducting research in analytical testing, pipettes are generally used to remove small or trace amounts of liquids. Pipettes can be divided into gas piston pipettes and external piston pipettes according to the principle. Gas piston pipettes are mainly used for standard pipetting, and external piston pipettes are mainly used to handle special liquids such as volatile, corrosive and viscous. Many people ignore the correct use of pipettes and some of the details.
How to choose a pipette correctly?
1. Product performance, that is, the accuracy and repeatability of the pipette. For the vast majority of users, testing product performance before purchasing is both difficult and unnecessary. Therefore, it is mainly based on the technical data provided by the manufacturer. But don't take the seller's word of mouth lightly, be sure to check the written materials provided by the manufacturer.
2. The reliability and durability of the product mainly depend on the material used for the pipette. For the housing, it should have high impact resistance, corrosion resistance and low 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 you need to factor in the purchase price and longevity.
3. The ergonomic design of the product can mainly consider the following points:
First, the short travel distance of the thumb to complete a pipetting cycle means greater comfort;
Second, compare the thumb force required for a pipette of the same range to complete one discharge (must be pressed to the end), which is the key to affecting comfort. The less force means the less risk of finger damage caused by long-term use;
Third, when loading and unloading the suction head, the more labor-saving 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 slightly poor;
Fifth, other auxiliary designs, such as the frosted design of the shell and the design of the finger hooks, help to further improve the comfort.
How to use a pipette correctly?
① Range adjustment
When adjusting the range, if you want to adjust the volume 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 the volume from a small volume to a large volume, you can first rotate the scale knob clockwise until more than The scale of the range, and then back to the set volume, so as to ensure the highest accuracy of the measurement. During this process, do not turn the button out of range, as this will jam the internal mechanism and damage the pipette.
②Assembly of the pipette tip (aspirator)
When putting the pipette tip on the pipette, many people will knock on the pipette tip box a few times. This is a wrong approach, because this will cause the internal parts of the pipette (such as springs) to be instantaneously generated by the knocking. The force of impact can become loose, and even cause the scale adjustment knob to jam. The correct method is to insert the pipette (device) vertically into the pipette head, and turn it slightly left and right to make it tightly combined. If it is a multi-channel (such as 8-channel or 12-channel) pipette, you can align the first channel of the pipette with the first tip, then insert it obliquely, and shake it back and forth to lock it. The tip is clamped slightly over the O-ring, and you can see that the connection part forms a clear seal.
③ Method of pipetting
Before pipetting, ensure that the pipette, tip and liquid are at the same temperature. When aspirating the liquid, keep the pipette upright and insert the pipette tip 2-3 mm below the liquid surface. Wet the nozzle by aspirating the liquid a few times before suctioning (especially if you are picking up liquids that are viscous or have a different density than water). There are two pipetting methods available at this time. One is forward pipetting. Press the button with your thumb to the first stop, then slowly release the button to return to the origin. Then press the button to the first stop point to discharge the liquid, stop for a while and 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, easily foaming liquids or extremely small amounts of liquids. 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, keep pressing the button at the first stop point (never press it down again), remove the pipette tip with residual liquid, and throw it away.
④ Correct placement of the pipette
After use, it can be hung upright 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, so as to prevent the liquid from flowing back and corroding the piston spring.
How to maintain and maintain the pipette?
If not in use, adjust the range of the pipette to the maximum scale, so that the spring is 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 rinse with distilled water, and let it dry naturally.
Before autoclaving, make sure that the pipette can handle the heat. Calibration can be carried out by repeating the weighing of distilled water in a 20-25 degree environment. Check for leaks during use. In the method, suck the liquid and place it vertically for a few seconds to see if the liquid level drops. If there is leakage, the reasons are roughly as follows:
①Whether the gun head matches;
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. You can aspirate the liquid a few times before pipetting.
