What is Dispensing?
The term ‘dispensing’ refers to discharging of defined quantities of a liquid substance. In order to facilitate easier, quicker and more accurate dispensing of chemical reagents, researchers are widely using bottle top dispensers. This instrument has essentially replaced the method of pouring liquids into graduated measuring cylinders. Bottle top dispensers are either installed directly on commercial laboratory bottles or mounted through the use of adapters.
Fundamental Working Principle of Bottle Top Dispenser
A bottle top dispenser works through an upward movement of a piston, which allows the aspiration of a specific amount of liquid present in the reagent bottle into a lab container. Additionally, through the piston’s subsequent downward motion, the reagent is released through a valve and discharge tube. Bottle top dispensers eliminate the need to set a meniscus, which helps in expediting the liquid transfer process.
There are different types of pistons used in a bottle top dispenser. One of them is known as the ‘floating piston’ and the other is called the ‘wiping-seal piston’. Let’s understand the key points of difference between the two kinds of pistons.
Bottle Top Dispenser with Floating Piston
Such system does not need any piston seal which makes it highly durable and easy to maintain due to less friction wear. A floating piston gets fitted into the dispensing cylinder without making contact with the surface. This means that the piston and dispensing cylinder are apart by a gap (a few thousandths of a millimeter wide). This liquid that needs to get transferred creates a thin film within the gap and acts as a lubricant for the piston for a smooth movement.
In some cases, liquid residues can get deposited in the gap between the piston and the cylinder, leading to a higher risk of crystal formation.
Bottle Top Dispenser with Wiping-seal Piston
Such kind of bottle top dispenser features a wiping-seal in addition to the floating piston system. Dispensers having wiping seal pistons usually require higher operating force during the process of liquid transfer. This is responsible for causing defective sealing due to friction wear and tear.
Bottle top dispensers with wiping-seal pistons can be used in experiments involving a variety of daily-routine and less aggressive reagents, such as acids and bases having low concentrations, biological buffers, polar solvents, biological detergents and cell culture media.
In order to eliminate the higher operating forces during liquid filling, some systems use a spring with automatic lifting action that reduces the friction.
Why botte top dispensers with wipe-seal pistons are better
- It has a typical sealing lip at the lower end of the piston used to wipe the inside surface of the container.
- A wiping-seal piston enables the complete transfer of the liquid, thereby reducing the risk of crystal formation inside the container.
- As the piston is protected from swelling or freezing, it makes dispensing of highly viscous liquids possible.
Bottle Top Dispensers by Microlit
Microlit Bottle top dispensers featuring wiping-seal piston technology have a range of designs with a myriad of powerful features and functionalities. Microlit’s bottle top dispensers have cutting-edge EasyKnob™ and FlexiNozzle™ technologies which greatly enhance their flexibility and ease of use. In addition, our designs are equipped with recirculation valve modes, which help in preventing loss of reagent during purging.
The dispensers are compatible with a variety of chemicals and are autoclavable. Designed by our expert team of product engineers, the products are highly intuitive and ergonomic, making them ideal for achieving precision and reliability in practical laboratory environments.
The instruments feature a PTFE Piston with an ETP O-Ring, which helps the dispenser to move smoothly and effortlessly. The piston parts are also extremely compatible with a wide range of chemicals. Our bottle top dispensers are calibrated in an ISO 17025 accredited laboratory and comply with ISO 8655 standards. We also provide a calibration certificate inside the product package, in addition to a calibration tool which can be used for a quick in-lab recalibration.