In the research of analytical testing, a pipette is generally used to measure a small amount or a small amount of liquid. The correct use of the pipette and some of its details are ignored by many people. It is now detailed in several aspects.
Range adjustment
When adjusting the range, if you want to adjust from a large volume to a small volume, follow the normal adjustment method, turn the knob counterclockwise; but if you want to adjust from a small volume to a large volume, you can first rotate the scale knob clockwise to over The scale of the range is then adjusted back to the set volume, which guarantees the highest accuracy of the measurement.
During this process, never push the button out of the range, otherwise it will get stuck in the internal mechanism and damage the pipette.
Assembly of the tip (suction nozzle)
When putting the pipette tips on the pipette, many people will knock on the tip box a few times. This is a mistake because it can cause internal components (such as springs) of the pipette. The instantaneous impact force generated by the tapping becomes loose and may even cause the scale adjustment knob to become stuck. The correct way is to insert the pipette (gun) vertically into the tip of the gun, and use a slight force to rotate it slightly to make it tightly bond. If it is a multi-channel (such as 8- or 12-channel) pipette, you can align the first line of the pipette with the first head, then insert it obliquely, and shake it in the front-rear direction. The logo of the gun head is slightly over the O-ring and the connecting part can be seen to form a clear seal.
Pipetting method
Before pipetting, ensure that the pipette, tip, and liquid are at the same temperature. When pipetting the liquid, the pipette is held upright and the tip is inserted 2-3 mm below the surface. Before aspirating, you can first aspirate the liquid several times to wet the liquid suction nozzle (especially when you want to absorb a liquid that is thick or different in density from water). Two pipetting methods can be used at this time.
The first is the forward pipetting method. Press the button to the first stop with your thumb, then slowly release the button to return to the origin. Then press the button to the first stop to discharge the liquid, and then stop for a while and continue to press the button to the second stop to blow out the residual liquid. Finally release the button.
The second is the reverse pipetting method. This method is generally used to transfer highly viscous liquids, biologically active liquids, easily foaming liquids or very small amounts of liquids. The principle is to inhale more liquid than the set range first, and it is not necessary to blow out the residual liquid when transferring the liquid. Press the button first 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 hold button at the first stop point (do not press down again), remove the gun head with residual liquid, and discard it.
Correct placement of the pipette
After use, you can hang it vertically on the pipette holder, but be careful not to fall off. When there is liquid in the pipette tip, do not place the pipette horizontally or upside down to prevent the liquid from flowing back to corrode the piston spring.
Precautions during maintenance
If not used, adjust the range of the pipette to the maximum value to keep the spring in a relaxed state to protect the spring.
It is best to clean the pipette regularly, either with soapy water or 60% isopropanol, then with distilled water, and air dry.
Before autoclaving, make sure the pipette is suitable for high temperatures.
Calibration can be carried out by repeatedly weighing distilled water in a 20-25 degree environment.
Check for leaks during use. The method is to take the liquid and then hang it vertically for a few seconds to see if the liquid level drops. If there is leakage, the reasons are as follows:
1. Whether the gun heads match;
2. Whether the spring piston is normal;
3. If it is a volatile liquid (as is the case with many organic solvents), it may be a problem of saturated vapor pressure. You can suck up the liquid several times before pipetting.
The selection of pipettes should consider the following aspects
1. High quality performance
2. Unique volume control system
3. Consistent accuracy and repeatability
4. Reliable and durable
5. Ergonomic design
If a pipette can have both variable or fixed capacity, it means that there is both a variable range piston and a fixed range piston in a pipette. This means that the brand pipette offers users two functions at the price level of a single pipette. The function of some brands of pipettes is not limited to this, not only does each pipette have a fixed capacity piston, but you can also purchase fixed pistons of other ranges installed on the pipette, the price is far lower than the purchase The price of a fixed-range pipette. With this method, you can choose a fixed-range pipette according to your needs, which is economical and convenient.
Accuracy and reproducibility
The accuracy and repeatability of the pipette is an important indicator of the purchase, which is directly related to the actual analysis and testing can be carried out smoothly. Air control principle of Danish Capp pipette
Many brands of pipettes do not pay enough attention to temperature uniformity. The Danish CappAero pipette is the only pipette that uses internal temperature uniformity as an important means of ensuring the accuracy of the pipette. In order to effectively ensure uniform internal temperature, the brand also deliberately designed a patented air compartment handle, the air inside the handle is automatically Exchange with the outside world, this result guarantees a more accurate loading, especially in the case of long-term use.
Is the pipette combined with the Tip head suitable?
The combination of the pipette and the Tip head is a guarantee of accuracy and reproducibility. Generally, the combination of the pipette and the Tip is in the form of a direct bayonet. This method is relatively firm, but the Tip head is replaced. It needs to be more difficult. For a long time, the combination of the pipette and the Tip head will have a bad influence, which may greatly affect the sampling accuracy. Some brands of pipettes have double O-rings to ensure that the error during loading is less than 1% of the set error. O-rings make the combination more precise, reducing inaccuracies. This type of pipette can be used as a reference when purchasing, because this pipette can fit more Tip heads.
