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Reverse Pipetting
Reverse pipetting is a technique to dispense a measured quantity of liquid by means of air displacement pipette. The technique is mainly recommended for solutions with a high viscosity or a tendency to foam: as it reduces the risk of splashing, foam or bubble formation. Reverse pipetting is more precise in dispensing small volumes of liquids containing proteins and biological solutions compared to forward pipetting, which is mostly used for aqueous solutions, such as buffer solution, buffers, diluted acids or alkalis. How it works In reverse pipetting, the volume aspirated to the tip is bigger than the volume delivered to the receiving vessel. The excess of volume compensates for the liquid that remains as film inside the tip during dispensing. Liquid aspiration is achieved by creating vacuum by means of the vertical travel of a metal or ceramic piston within an airtight sleeve. As the piston moves upward, driven by the depression of the plunger, a vacuum is created in the sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Displacement Pipette
Piston-driven air displacement pipettes are a type of micropipette, which are tools to handle volumes of liquid in the microliter scale. They are more commonly used in biology and biochemistry, and less commonly in chemistry; the equipment is susceptible to damage from many organic solvents. Operation These pipettes operate by piston-driven air displacement. A vacuum is generated by the vertical travel of a metallic or ceramic piston within an airtight sleeve. The upward movement of the piston, driven by the depression of the plunger, creates a vacuum in the space left vacant by the piston. To fill the vacuum, air from the tip rises, which is then replaced by the liquid that is drawn up into the tip and thus available for transport and dispensing elsewhere. Sterile technique prevents liquid from coming into contact with the pipette itself. Instead, the liquid is drawn into and dispensed from a disposable pipette tip that is discarded after transferring fluid and a new pipette ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscosity
Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for example, syrup has a higher viscosity than water. Viscosity is defined scientifically as a force multiplied by a time divided by an area. Thus its SI units are newton-seconds per metre squared, or pascal-seconds. Viscosity quantifies the internal friction, frictional force between adjacent layers of fluid that are in relative motion. For instance, when a viscous fluid is forced through a tube, it flows more quickly near the tube's center line than near its walls. Experiments show that some stress (physics), stress (such as a pressure difference between the two ends of the tube) is needed to sustain the flow. This is because a force is required to overcome the friction between the layers of the fluid which are in relative motion. For a tube ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forward Pipetting
Forward pipetting is a technique to dispense a measured quantity of liquid by means of air displacement pipette. The technique is mainly recommended for aqueous solutions, such as buffers, or diluted acids or alkalis. In case of solutions with a high viscosity or a tendency to foam, reverse pipetting is more suitable. How it works In forward pipetting, an exactly set volume of liquid is aspired to the tip and then it is delivered to a new vessel. This is achieved by creating vacuum by means of the vertical travel of a metal or ceramic piston within an airtight sleeve. As the piston moves upward, driven by the depression of the plunger, a vacuum is created in the space left vacant by the piston. Air from the tip rises to fill the space left vacant, and the tip air is then replaced by the liquid, which is drawn up into the tip and thus available for transport and dispensing elsewhere. When the pipette knob is pressed on an air displacement pipette, the piston inside the instrumen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buffer Solution
A buffer solution is a solution where the pH does not change significantly on dilution or if an acid or base is added at constant temperature. Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. In nature, there are many living systems that use buffering for pH regulation. For example, the bicarbonate buffering system is used to regulate the pH of blood, and bicarbonate also acts as a buffer in the ocean. Principles of buffering Buffer solutions resist pH change because of a chemical equilibrium between the weak acid HA and its conjugate base A−: When some strong acid is added to an equilibrium mixture of the weak acid and its conjugate base, hydrogen ions (H+) are added, and the equilibrium is shifted to the left, in accordance with Le Chatelier's principle. Because of this, the hydrogen ion concentration increas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pipette Knob Held By Robot
A pipette (sometimes spelled as pipet) is a type of laboratory tool commonly used in chemistry and biology to transport a measured volume of liquid, often as a media dispenser. Pipettes come in several designs for various purposes with differing levels of accuracy and precision, from single piece glass pipettes to more complex adjustable or electronic pipettes. Many pipette types work by creating a Vacuum, partial vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid. Measurement accuracy varies greatly depending on the instrument. History The first simple pipettes were made of glass, such as Pasteur pipettes. Large pipettes continue to be made of glass; others are made of squeezable plastic for situations where an exact volume is not required. During or prior to 1877, Joseph Lister (1827 – 1912) invented the first adjustable micropipette, consisting of a "pipette with a syringe" (photograph shown at right). The micr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
