Choose the Best Bottle Top Dispenser for Your Work

Bottle top dispensers are an essential item of laboratory equipment for effective and repeatable dispensing of reagents and chemicals. When using a bottle top dispenser, the liquid comes into direct contact with the dispenser’s barrel and plunger. Bottle top dispensers can be adapted to ensure plunger protection; therefore it is important to understand when you should use plunger protection and when it is not necessary for your application.

Here are the benefits and limitations you should consider when choosing a new dispenser:

Plunger with protection layer

• Fluorinated polymers such as PTFE, FEP and PFA are most commonly used to manufacture plunger protection layers and have a variety of benefits, including:
• Excellent chemical resistance.
• Very smooth surfaces that resist the build-up of biofilms and crystals in the plunger.
• Oleophobic and hydrophobic properties, and low binding capacities with liquids such as water and aqueous solutions.
• Low liquid permeability.
• Reduced coefficient of friction compared to uncoated glass surface plungers.
• Food contact compliance (FDA compatibility).
• When using salt solutions, acids, bases or buffers, a protection layer prevents plunger freezing when liquid remains in the instrument.
• Protection layers can be mechanically fragile and scratches may hinder how the dispenser works. This can be resolved by using a sufficiently thick coating to improve the mechanical stability.
• Organic solvents and some strong acids at high concentrations may react with the coating. This may lead to layer swelling or peeling in extreme cases.

Plunger without protection layer

• Plungers are usually made of ground glass or ceramic materials that have good chemical stability. Liquids that could potentially react with fluorinated polymer protection layer are suitable for use with glass and ceramic materials.
• When using ground glass as the plunger material, it can be difficult to guarantee a smooth glide of plunger in the barrel. Manufacturers must find the best compromise between appropriate surface roughness and capillarity effects. This is only possible when plungers are machined with very highest precision.
• Some liquids can exhibit high friction, making the plunger difficult to use.
• There is a greater sensitivity to plunger freezing when the dispenser is not in use and capillary effects can lead to the plunger sticking during plunger activation.
• Ceramics have excellent chemical resistance and an improved mechanical shock resistance compared to glass. However, it is a highly expensive material and increasing the market price of the instrument.

It is important for users to identify the liquids they will be dispensing before selecting a suitable dispenser. Always check the recommended use and limitations of your instruments, and if required, contact the manufacturer for technical support.

The Socorex Calibrex^TM solutae 530 bottle top dispensers have PFA plunger protection layers and the Calibrex^TM organo 525 bottle top dispensers have ground glass plungers. Watch this informative video to learn more about the Calibrex^TM range.

Adapted from an article written by Yves Lachavanne, Marketing and Sales Support Manager, Socorex