Pipette is a common instrument and equipment used in mi […]
Pipette is a common instrument and equipment used in microorganisms and laboratories to pipette small amounts of liquid. The advantages are easy practical operation and high accuracy. With it, letting the laboratory pipette has not become the key cause of analysis deviation. For the things you must know about pipettes, you can see below!
1. The pipette is a new upgrade of pipettes
More than a hundred years ago, the elites in the laboratory just started using pipettes to move liquids. To put it bluntly, the pipette is a hollow glass test tube with one to N scales marked on it. Insert each glass test tube into the liquid, use your mouth on the other end of the water pipe (at first, the elites only use their precious lips to do this work) or ear wash ball to suck the liquid into the water pipe, and the top The ruler tells you how much liquid is in it. After sucking in the amount that everyone needs, plug the end of the liquid with your thumb, and then put the water pipe into another vessel, and let the liquid in the water pipe into this second vessel. Then everyone's daily task of migrating liquids is taken!
As everyone knows, with the development of social development, the elites find that this water pipe is really not easy to use, tired and slow, and not easy to clean. So lazy thoughts accumulate in the brain, accumulate, and then explode-so the pipette came out! In other words, the function of the pipette and the pipette are the same, the only difference is: 1. High accuracy Some (according to the comparison with the old pipette, the precision of some new pipettes is also very good); two, higher efficiency and higher (easy to operate); third, the structure is more complicated (the pipette is more convenient) It is a water pipe, and the pipette is composed of dozens of components); Fourth, the function is more powerful (in addition to pipetting, many pipettes also have many functions); Fifth, the most important point, the price is higher ! (The price of new technology will undoubtedly be higher.)
2. The principle of the pipette
Regarding the plain instrument, in most cases it is always necessary to carefully introduce the basic principle of its incomprehension, but the basic principle of the pipette is very simple-it is to make the piston rod move around the theme according to the elastic telescopic energy , Drain or draw liquid.
Generally speaking, there are two types of pipettes, one is a gas-replacement type; the other is an external piston machine, which is often used as a unique pipette, and has a narrow application range. This type of pipette can be used Remove the sample with high viscosity.
To put it bluntly, the gas displacement type is the diastolic pressure piston rod, which presses out the gas inside the pipette. Later, when the piston rod is displaced, the standard pressure inside the pipette is lower than the outside standard pressure. The liquid can be sucked up under the effect of the external standard air pressure. To put it simply, the gas comes out and the liquid comes in!
To put it bluntly, the external piston machine is actually exactly the same as the principle of the needle tube. After seeing the whole process of the needle tube, you can probably figure out the basic principle of the external piston machine.
The principle of related pipettes and interested customers can view the content of Leibe’s previous articles. Leibe has already done the actual details in the "Selection and Use of Pipettes-Pipette Structure, Principle and Pipetting Mode" Introduction.
3. Volume adjustment of the pipette
The first pipettes could not adjust the volume, which is the fixed volume pipette currently on the market. For example, if you buy a 200ul pipette, the volume of liquid that is migrated each time is only 200ul. With the passage of time, this type of pipette has long been difficult to consider the necessity of contemporary scientific research workers. Although most well-known brands also manufacture fixed-volume pipettes, relatively few customers have bought them.
As the requirements were different, a pipette with adjustable range appeared later, but at that time there were fewer ranges to choose from. To give another example: if you buy a 200ul pipette, it has 4 gears, namely 200ul, 150ul, 100ul, 50ul. In other words, with this pipette, the volume of liquid you can migrate can be selected among the 4 gears here, which is much more convenient than the original fixed-volume pipette. As everyone knows, the range selection of this type of pipette is also limited after all, and it is also impossible to completely meet the requirements of customers. Therefore, everyone classifies this type of pipette as a fixed-range pipette.
However, the popular pipettes on the market today are all adjustable volume pipettes that can be adjusted freely within a certain range. Generally speaking, the range adjustment range of a pipette is 10%-100% of the larger range indicated by it. Take the 200ul pipette as an example: if you buy a 200ul adjustable volume pipette, you will be able to move liquid freely within the volume range of 20-200ul. This is much more convenient for everyone to use, but still special attention is that for a special pipette at random, the smaller the volume of the transferred liquid, the lower the general precision.
4. Number of safe channels of pipette
From the first pipette to the current popularity of the pipette sales market, there are pipettes that only transfer one part of the liquid sample each time, which is called a single-channel pipette. However, with the rapid development of the biological science industry, in many cases single-channel pipettes represent high efficiency but not high efficiency. For example, if you want to fill a 96-well plate (a 96-well plate is a plastic plate with 96 wells, each well can hold a certain volume of liquid), you must use a single-channel pipette Repeating the actual operation of pipetting 96 times is not a beautiful job. I firmly believe that many people who experience this kind of work experience are deeply moved. If you want to continuously fill up several 96 plates, then one word is tired! Therefore, a multi-channel pipette appears, which means that several liquid samples can be transferred in one pipetting operation. This type of pipetting The device is also known as "platoon gun". Nowadays, there are many kinds of multi-channel pipettes on the sales market, such as 6, 8, 12, 16, 24, and even 36, 48, 64 and 96 channels (the dealer calls 96 channels) Pipetting Service Center). For example, an 8-channel pipette can transfer 8 liquid samples at a time, and so on for other types. Naturally, 8-channel and 12-channel pipettes are the most sold on the market. Therefore, there are few manufacturers of pipettes with 16 channels and above, and there is even only one type of pipette. manufacturer.
5. The actual operation of the pipette TIPS
The actual operation of the pipette has some tricks. The actual operation of how to select the range and manipulate the aspiration level is a lot of difficult problems that puzzle the practical beginners. The following are the key common problems of the pipette:
Install the pipette tip:
After entering the pipette tip at the bottom of the pipette handle, if you are actually operating in the tip box, gently shake the pipette up and down or slightly rotate the pipette (only single-channel pipetting). The device can be rotated) for 1-2 seconds; if you use a loose weighing tip, use the handle tip to gently apply pressure to the pipette position and rotate the tip for 1-2 seconds. If this kind of actual operation cannot achieve the ideal airtightness, it is necessary to check the tip and the pipette.
Selection range of laboratory pipette:
On the whole, the usable range of the pipette is 10-100% of the larger range of the pipette.
The best proposal based on actual operating experience is: the best range of the pipette is 35-100% of the larger volume of the pipette.
The pipette manipulates the rate of aspiration:
During the whole process of pipetting, the working pressure of the thumb must be gradually reduced to make the liquid rise symmetrically and slowly in the tip.
The depth and perspective of laboratory pipette manipulation and aspiration:
(1) In-depth regulations for pipette tip penetration:
The deep layer of aspiration needs to ensure that the required pipette volume is achieved;
The pipette keeps the tip surface from touching the liquid as much as possible.
(2) The perspective of pipette pipetting: The pipette must be kept in a vertical position throughout the entire process of pipetting.
About pipette waiting time:
The pipette is designed for large-scale pipetting (ml level) and the pipetting of samples with significantly higher viscosity than water. After releasing the thumb during aspiration, the pipette tip must stay in the liquid for 3-5 seconds before pipetting except
Laboratory pipette storage:
After the pipette application is completed, the pipette must be adjusted to a larger range, and then offline (can be hung on a special support frame, or hung on the metal bar of the test bench cabinet). To be skilled in the actual operation of the pipette, you must grasp the above several aspects.