Pipettes are instruments commonly used in biological and chemical laboratories to remove trace amounts of liquids. The advantages are easy to operate and high accuracy. With it, laboratory pipetting is no longer the main reason for analysis errors.
For those things you have to know about pipettes, see below!
1. The pipette is an upgraded version of the pipette
More than a hundred years ago, the elite in the lab began using pipettes to transfer liquids. The so-called pipette is a hollow glass tube with one to N scales. Insert the glass tube into the liquid and use the mouth on the other end of the tube (in the beginning, our elites can only use their precious mouth to dry the work) or wash the ear to suck the liquid into the tube, while above The scale tells us how much liquid is inside. After filling the amount we need, plug the end of the aspiration with your thumb, then place the tube in another container and let the liquid in the tube flow into the second container. This way we will be able to transfer the liquid!
However, with the advancement of society, the elites found that the pipe was not easy to use, tired and slow, and it was not very clean. So the lazy thoughts accumulate in the brain, accumulate, and then erupt – so the pipette is born!
That is, the pipette and the pipette have the same effect, the only difference is:
First, the accuracy is even more High (based on the accuracy of some elites in new pipettes compared to old pipettes);
second, higher efficiency (easy to operate);
third, more complex structure (pipette is one The root pipe, while the pipette is made up of dozens of parts);
Fourth, the function is more powerful (in addition to pipetting, many pipettes have many functions);
Fifth, and most importantly, the price is higher (The price of high technology will definitely be higher.)
2. The working principle of the pipette
For so-called precision instruments, most of the time, we must seriously introduce its esoteric principles, but the principle of the pipette is very simple – the piston is moved up and down by the telescopic force of the spring to discharge or suck the liquid.
Generally speaking, pipettes are divided into two types, one is air displacement type; the other is external piston type, which is often used as a special pipette, and the application range is relatively narrow.
This type of pipette can be used. Used to remove samples with high viscosity.
The so-called air displacement type is to press the piston to press the air inside the lower end of the pipette, and then when the piston moves up, the air pressure inside the lower end of the pipette is smaller than the external air pressure, so that under the action of the external air pressure You can suck up the liquid. In short, the air goes out and the liquid comes in!
The so-called external piston type is actually the same as the syringe. When you see the working process of the syringe, you can probably understand the principle of the external piston.
For those interested in the working principle of pipettes, please refer to the previous article by Lebe, which has been specifically introduced in “Selection and use of pipettes – structure, principle and pipetting mode of pipettes”. .
3. Pipette range adjustment
The original pipette was unable to adjust the range, which is the fixed-range pipette on the market today.
For example, if you buy a 200ul pipette, the volume of liquid transferred each time can only be 200ul. Over time, this type of pipette has been difficult to meet the needs of modern researchers. Although most brands also produce fixed-range pipettes, the relative number of users has been reduced.
Depending on the demand, a pipette with adjustable range was introduced, but at that time there was less range available. Continue with the example: If you buy a 200ul pipette, it has 4 gears, 200ul, 150ul, 100ul, 50ul. In other words, with this pipette, the volume of liquid that you can transfer can be selected between these four gears, which is much easier than the original fixed-range pipette. However, the range selection of this pipette is also limited, and it is also unable to fully meet the user’s requirements. Therefore, we classify this pipette as a fixed-range pipette.
The mainstream pipettes on the market today are adjustable range pipettes that can be adjusted freely within a certain range. In general, the range of a pipette is adjusted from 10% to 100% of the maximum range it is labeled. Or take a 200ul pipette as an example: If you buy a 200ul adjustable range pipette, you can freely transfer liquid in a volume range of 20-200 ul. This greatly facilitates our users, but it should be noted that for any particular pipette, the smaller the volume of liquid transferred, the lower the general accuracy.
4. Number of channels of the pipette
From the first pipette to the current mainstream of the pipette market, there are pipettes that can only transfer one liquid sample at a time, which we call a single-channel pipette. But with the rapid development of the life sciences, many times single-channel pipettes mean inefficiency.
For example, if you want to fill a 96-well plate (a 96-well plate is a 96-well plastic plate that holds a certain volume of liquid), you must repeat 96 moves with a single-channel pipette. Liquid operation, this is not a bad thing, I believe many people who have had this experience will be deeply touched. If you want to fill multiple 96 plates continuously, then one word – tired!
So, there are multiple pipettes, which can transfer multiple liquid samples in one pipetting operation. This pipette is commonly called ” Row guns.” Now, there are many kinds of multi-channel pipettes on the market, such as 6, 8, 12, 16, 24, or even 36, 48, 64, and 96 (the supplier calls 96 moves). Liquid workstation).
For example, an 8-channel pipette can transfer 8 liquid samples at a time, and so on. Of course, the most used in the market are 8-channel and 12-channel pipettes, so there are not many manufacturers of pipettes that produce 16 or more channels, and there are only one manufacturer.
5 pipette operation TIPS
There are some tricks in the operation of pipettes. How to select the range and control the operation of pipetting is a common problem that plagues novice operators. The following are the key points for pipettes:
Install the pipette tip:
After entering the tip at the lowermost end of the pipette handle, if operating inside the tip box, shake the pipette left or right while gently pressing down or slightly rotate the pipette (only the single pipette can be rotated) ) 1-2 seconds; if using a bulk tip, gently press the tip for 1-2 seconds while gently pressing the tip in the direction of the pipette. If this operation does not achieve the desired seal, it is necessary to check the tip and pipette.
Laboratory pipette selection range:
Overall, the available range of pipettes is 10-100% of the maximum range of pipettes.
The best advice based on operational experience is that the optimal range of the pipette is 35-100% of the maximum range of the pipette.
The pipette controls the rate of pipetting:
During the pipetting process, the pipette must slowly lower the pressure of the thumb to make the liquid rise evenly and slowly in the tip.
The laboratory pipette controls the depth and angle of the aspiration:
(1) Depth requirements for pipette tip immersion:
The depth of the aspiration should be such that the desired pipette volume is achieved;
The pipette keeps the outer wall of the tip as little as possible in contact with the liquid.
(2) Pipette pipetting angle: The pipette must be kept in the vertical state during pipetting.
About pipette dwell time:
Pipettes for large-scale pipetting (ml class) and viscosity is significantly higher than the pipetting of water samples, after releasing the thumb during pipetting, the tip must be allowed to stay in the liquid for 3-5 seconds before it can be removed.
Laboratory pipette storage:
After the pipette has been used, the pipette must be adjusted to the maximum range and then hung up (can be hung on a dedicated stand or attached to the metal crossbar of the lab bench). Proficiency in the use of pipettes must master the above requirements.
