A pipette is one type of lab instrument which uses to measure out or dispense small amounts of liquid in milliliters (mL) or microliters (μL) volumes. There have three types of this instrument namely glass, plastic, and electronic pipette. Borosilicate glass is used to make a glass type of this instrument. Plastic types of this instrument are constructed with polyethylene terephthalate (PET), and microprocessors run the electronic type of this instrument.
It is generally made with plastic and glass which are commonly used to measure volumes under 1 milliliter (mL). It can measure 0.1 microliters (μL) volume with an electronic type of this instrument. It has various range of experiment procedures in chemistry, medical research, molecular biology (biotechnology), and experiments in the general field of natural science, analysis of various foods and chemicals, food safety-related inspections, and biochemical-based clinical examination inspections. It is essential to practice good pipetting for getting good data accuracy.
Principle of Pipette
There exist two mechanisms, namely, the air displacement method and the positive displacement method which are followed. Each type consists of a piston that moves inside a capillary or cylinder. There can flow a specific amount of air between the piston and the liquid in air displacement pipettes. The piston makes direct contact with the fluid in positive displacement pipetting.
Air displacement method: In this method, there can possible the telescoping movement of the spring enables the piston to suction and discharge liquids. Some air is let out during the push of the piston and the liquid is drawn in by atmospheric pressure. Then the air is subsequently forced out to release the liquid. It can be managed by The pace and force of the pipetting while using a pipette because it is operated by following the spring’s expansion and contraction characteristics.
Positive displacement method: The positive displacement method involves direct contact with the liquid made by a disposable piston that moves inside the tip. The tested sample is drawn easily into the tip by the piston’s upward movement. The chosen volume is discharged after descending the piston.
Parts
There exist some parts which are described below:
Plunger: This part relates to aspirating and dispensing the desired volume of liquids.
Ejector button: It helps to eject the liquid from this device.
Volume Adjustment Knob: This part helps to transfer the different volumes of the sample by rotating the volume adjustment knob to increase and decrease the concentration.
Volume window: It shows the volume of the sample, and the place values shown depend on the size of this instrument.
Shaft: This part is a tube-like structure and is filled with air in an air displacement type. Some air from the shaft is released at the time of pressing the piston.
Tip cone: The tip is attached to this area.
Pipette tip: This part is made of polypropylene or plastic and comes into contact with the liquid.
Types
Pasteur type
This type is also called an eye dropper or simply a dropper. Generally, they are made of glass and related to mediate the transfer of small amounts of liquids.
Volumetric type
This type is also called bulb pipette or belly pipette which is generally used in the field of analytical chemistry for making various laboratory solutions from stock and preparing solutions for titration. The volumetric pipettes are very useful for measuring quickly up to 4 significant digits.
Graduated type
These types have indicated volume increments alongside the tube which have various shapes and are frequently used for straightforward solution transfers.
Vacuum-assisted type
These types help to measure a single volume and hence only have one graduation mark, graduated vacuum-assisted types use multiple graduation marks. These pipettes are made of polystyrene, glass, or borosilicate.
Repeater type
These types are suitable for dispensing the same quantities repeatedly into several receptacles without pausing in between each dispensing process, increasing speed and efficiency. These pipettes have a small weight and only require one hand to operate and enabling a single operator to work at a throughput capacity.
Operating Procedure
Firstly, take a tip out of the tip box by applying the load. Then adjust the volume to be transferred the solution. Press the plunger for stopping quickly. Then tip inside the tube or container where the liquid is stored. Finally ejector button should be pressed to remove the used tip and place it in the proper garbage can.
Applications
This instrument is generally used to transport liquids in precise measurements. It has a wide range of applications in molecular biology, chemistry, and medical testing.
Advantages
It is convenient to handle hazardous chemicals by using this device. Foaming liquids, high vapor pressure liquids, and liquids with a high viscosity can be transferred from one container to another container by using this instrument.
Disadvantages
The volumetric type of this instrument is more expensive, and its measurements are fixed to the individual volumetric type.
