Choosing the right pipette for your application Find the right BRAND pipetting system for your application

The criteria used to select the optimal device are as varied as the different models on the market. The properties of the medium used are often the limiting factor in the selection process and determine the use of a positive displacement pipette. The properties of the medium used is therefore one of the most important criteria in selecting a suitable dispensing system. There is often a large selection even within a group and there are usually many different models that all work according to the same principle.

For this reason, the requirements of the application must also be considered. For example, it is necessary to check how often a delivery must be repeated, which vessels are used, or which volume is required. A device must therefore optimally support users in their work; it must be intuitive to operate, deliver accurate 
volumes, and meet the necessary requirements.

The following explanations are intended to show the differences between the individual devices so that a decision can be made more easily.

The medium used has a decisive influence, especially in devices that work according to the air displacement principle, and can negatively affect the accuracy of dispensing. Certain media can make precise and reproducible work with the air displacement models difficult or even impossible:
 

• High viscosity or wetting media
• High density media
• Foaming media (e.g., detergents)
• Highly volatile liquids
• Infectious media
   

With a certain amount of experience and using special techniques (e.g., reverse pipetting, the use of surface-treated low retention tips, saturation of the air cushion by repeated intake and delivery of the medium before the actual pipetting step, and working slowly), these media can also be used to some extent in air displacement models.  
Most frequently, high-viscosity media in particular, cause problems and inevitably lead to the change to positive displacement. Of course, proper technique (e.g., slow dispensing) offers optimization possibilities. But as can be seen from the viscosity limits of the individual devices, the differences are clear. 
 

In these or similar cases, a positive displacement model should be used. Because of the direct contact to the piston, 
the influence of the air cushion is eliminated, and exact working without loss of accuracy is guaranteed.  

In addition to the usability of the medium, the volume range can be a further criterion according to which the dispensing unit is selected. Devices such as the Transferpette®, which must work with high precision in small volume ranges, cover only a limited volume range. However, it is extremely important for the application that the desired volume can be dispensed in a single step in order to achieve reproducibility. It is therefore necessary to check which range must be covered and which device has the necessary requirements for this. 

Both the volume to be dispensed and the frequency of dispensing are decisive. In some experiments, each sample must be dispensed individually. However, it some cases, it is useful if a volume can be dispensed several times in succession or even in parallel. Here too, the possibilities are as varied as the applications themselves.  

Things become a bit more complicated if the desired vessels do not correspond to a standard SLAS/ANSI format. 
Multi-channel systems can not be used in such cases. BRAND also offers a convenient solution for this. With the Transferpette® electronic  in dispensing mode, the HandyStep® S, or HandyStep® touch/touch S, continuous multiple dispensing into each vessel is possible. 
Depending on the complexity of the application, it ranges from manual dispensing to complex series with the HandyStep® touch S. Here, too, the workload can be greatly reduced, and reliable and precise dispensing is guaranteed.

The following overviews summarize the criteria described above and provide a practical guide to choosing the right pipette.