What Is a Graduated Pipette?
A pipette, also called a pipette gun, is a metering tool that moves liquid from the original container to another container within a certain range. It is widely used in the fields of biology and chemistry.
- Chinese name
- Pipette
- Foreign name
- locomotive pipette
- According to the working principle, it can be divided into air displacement pipette and positive displacement pipette;
- They can be divided into single-channel pipettes and multi-channel pipettes according to the number of tips that can be installed simultaneously;
- It can be divided into fixed pipettes and adjustable pipettes according to whether the scale is adjustable;
- According to the way of adjusting the scale, it can be divided into manual pipettes and electric pipettes;
- According to special purposes, it can be divided into full disinfection pipettes, large-capacity pipettes, bottle-top pipettes, continuous injection pipettes, etc. [1] .
- Forward pipetting
- Press the pipetting operation lever to the first stop position, then slowly release the button to return to the original point; then press the pipetting operation lever to the first stopping point position to discharge the liquid, and pause for a while and continue to press the pipetting operation lever to the second stop Drain the residual liquid at the point position, and finally slowly release the pipetting lever.
- Reverse pipetting
- First press the button to the second stop position, slowly release the pipetting operation lever to return to the original point, and when the liquid is discharged, press the pipetting operation lever to the first stop point to discharge the set volume of liquid, and continue to hold the pipetting The operating lever is located at the first stopping point, and the tip with residual liquid is removed and discarded.
- In the process of adjusting the pipette, do not turn the knob too fast or exceed its maximum or minimum range, otherwise the amount may be inaccurate, and the internal mechanical device may be caught and the pipette may be damaged.
- In the process of assembling the tip, repeated repeated strong impacts with the pipette will not tighten it. If you do this for a long time, it will cause the parts in the pipette to loosen, and in serious cases, it will cause the knob to adjust the scale.
- When liquid is in the pipette tip, do not place the pipette horizontally or upside down, otherwise the liquid will flow backwards and corrode the piston spring.
- When sterilizing the pipette, you should first check whether the pipette used is suitable for high temperature sterilization before processing.
- Performance: accuracy and repeatability
- Durability / Maintenance: Pipettes have a long life and require very little maintenance or low maintenance costs
- Ergonomic principles: Comfortable feel, light suction and drainage operation, avoid repetitive muscle strain, low suction head force
- Choose a brand with manufacturer-qualified after-sales service.
- Remove the air bubbles from the pipette and select the scale to be calibrated.
- An empty container is tared on an electronic balance with an accuracy of 0.1 mg.
- Press the dosing key, add water to the empty container, weigh it, and record the reading.
- According to the national standard, the calibration of pipettes uses the "three-point test (100%, 50%, and 10% of the maximum range), six times per point" rule, and suppliers usually choose two rules: one is simple calibration, That is, two-point test (100% and 10% of the maximum range), four times per point; second, strict calibration, that is, three-point test (100%, 50%, and 10% of the maximum range), ten times per point. The user selects a rule according to his actual needs and enters the calculation link after completing the test. (Adjust according to the absolute difference between the average value and the actual value, and use a tool to tighten the tension of the spring buckle)
- A pipette, also called a pipette gun, is a metering tool that moves liquid from the original container to another container within a certain range. It is widely used in the fields of biology and chemistry.
Basic structure of pipette
- Pipettes are widely used in clinical laboratories because of their simple structure and ease of use. Its basic structure mainly includes several parts such as display window, capacity adjustment part, piston, 0-ring, suction tube and suction head (liquid nozzle) [1] .
How pipettes work
- The design of micropipettes commonly used in clinical practice is based on Hook's law: that the length of spring extension within a certain limit is proportional to the elastic force, that is, the volume of liquid in the pipette is proportional to the spring force in the pipette.
- There are two physics principles for adding micropipettes: using air pads and using positive piston displacement without air pads. These two different principles of micropipettes have different specific applications [1] .
Common classification of pipettes
Clinical application of pipette
- Clinical diagnostic laboratory, biotechnology laboratory, pharmacy and chemistry laboratory, environmental laboratory, food laboratory
How to use a pipette
- 1. Choose the right pipette
- When transferring standard solutions (such as water, buffers, diluted salt solutions, and acid-base solutions), use air to replace the pipette. Remove liquids with high volatility, high viscosity, and a density greater than 2.0g / cm. A positive displacement pipette was used for loading in the polymerase chain reaction (PCR) assay. Such as pipetting 15ul of liquid, it is best to choose a pipette with a maximum range of 20ul, and choosing a pipette with a range of 50ul or more is not accurate enough.
- 2. Set the pipetting volume
- Adjust the volume control by adjusting the volume control knob of the pipette. When adjusting the amount of pipetting, the scale should be rotated to a scale that exceeds the set volume, and then adjusted back to the set volume to ensure the best accuracy of the transfer.
- 3. Assemble the tip
- When using a single-channel pipette, align the nozzle cone of the adjustable pipette with the tip of the pipette tip and gently press down firmly to tighten it. When using a multi-channel pipette, align the first row of the pipette with the first nozzle, insert it at an angle, and shake it slightly back and forth to tighten.
- 4. Pipetting
- Make sure that the pipette, tip and the liquid to be removed are at the same temperature; then rinse the tip with the liquid to be removed 1-2 times, especially for thick liquids or liquids with a density different from water. When removing liquid, immerse the tip of the tip vertically to a depth of 2-3mm below the liquid surface (it is strictly forbidden to fully insert the tip into the solution), and slowly and evenly release the operating lever. Allow the tip to stand for 2-3 seconds after inhaling the solution. And obliquely attached to the container wall to drain excess liquid from the outer wall of the tip.
- 5. Placement of the pipette
- After using the pipette, use your thumb to hold down the tip pusher and press down. After safely exiting the tip, adjust its capacity to the maximum value indicated, and then suspend the pipette on a dedicated pipette holder; When it is not used for a long time, it should be placed in a special box [1] .
Pipette removal method
Pipette Precautions
Pipette maintenance
- The pipette should be maintained regularly according to the frequency of use, but at least every 3 months, check the pipette for dust and dirt, and pay special attention to its mouth cone. During long-term maintenance, the inside of the pipette needs to be cleaned, and it must be disassembled by trained and qualified personnel [1] .
- 1. Cleaning the pipette
- Cleaning the inside requires disassembling the lower half of the pipette. The removed parts are washed with soapy water, detergent or 60% isopropyl alcohol, rinsed with double distilled water, dried, and then coated with a cotton swab The top layer is a thin layer of lubricating silicone resin; the seal ring generally does not need to be cleaned.
- 2. Disinfection of the pipette
- Can be sterilized by conventional high temperature autoclaving or ultraviolet irradiation sterilization.
- 3.Removal of contaminated nucleic acids on pipettes
- Disassemble the inner and outer sleeves of the lower part of the pipette, soak them in the cleaning solution at 95 ° C for 30 minutes, then rinse the sleeves with double distilled water, dry or completely dry at 60 ° C, and finally place in the piston The surface is coated with a lubricant (silicone) and the parts are assembled.
Pipette selection criteria
Common pipettes
Micropipette
- Micropipettes are single-channel micropipettes for small volume pipettes commonly used in biological and chemical laboratories.
Pipette external piston pipette
- Due to different vapor pressure, density, and viscosity, some high-viscosity substances, such as oil and protein, cannot be absorbed. External piston pipettes do the job.
- Has the same accuracy and error coefficient as single-channel air-piston pipettes.
- External piston pipette
- Can be used for high viscosity liquids, such as protein and resin, the highest viscosity can reach 50,000mm2 / s, the highest density can reach 13.6g / cm3, such as mercury; high vapor pressure liquid, the highest vapor pressure can reach 500mbar, regardless of alcohol It's also some hydrocarbons that can be easily removed. There is also no problem with the removal of the foamable liquid.
Pipette bottle top pipette
- According to different models, it is usually used for the transportation of liquids with medium flow rate (0.5ml-100ml), such as acid, alkali, etc. According to the different properties of the liquid absorbed, it is divided into Dispensette III, Dispensette Organic and Dispensette HF. Can be sterilized as a whole at 121 ° C.
Pipette manual continuous pipette
- Can quickly and easily complete continuous pipetting work, can easily complete 2ul-5000ul reagent. Aspirate as many as 49 times. For viscous, high-density liquids and high vapor pressure liquids, they can also be accurately removed. Suitable for Plastibrand PD tips, Combitips tips and other piston tips.
Electronic continuous pipette
- Microprocessor controlled operation to automatically identify specific PD-tips
- The volume control range is from 1ul to 50ml, and 7.01ul, 70.1ul can be moved without any problems.
- Automatic dispensing, the electronic continuous pipette can be based on the average interval of three consecutive pipettes, and then dispense. (The required time can be calculated automatically without manual calculation and input).
- Intelligent charging, you can directly plug the electronic continuous pipette into the charger for charging, or remove the battery for charging. When replacing the backup battery, the original stored data will not be lost due to short power.
Electronic pipette
- Commonly used in food, pharmaceutical, petrochemical and other industries.
- Small size and long battery life, suitable for use in small spaces and away from power sources. The operation is simple. When inhaling the reagent, press the "Fill" key, and the handwheel rotates upward. If you start the titration, press the "Titr" key to start, and the handwheel rotates downward to start the titration volume. The digital display reduces errors caused by human readings and volume calculations. No tools required, users can calibrate themselves.
Pipette pipette calibration
- The cleaned pipette requires calibration. The pipette must be calibrated at room temperature (25 +/- 2 ° C). Refer to the instructions for use of the pipette. 10000 \ 5000 \ 1000 \ 200ul of different scales must be calibrated separately.
Pipette maintenance common sense
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