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Dispensing advice on pump technologies: bulk dispensing calls for a different set of requirements for every lab.

When it comes to bulk dispensing in a micro-plate format, there are no hard and fast rules. Every assay and every laboratory has a different set of needs; therefore, what works for one laboratory may not be appropriate for another. Primary considerations include throughput level, dispense performance, sterility and maintenance, reagent or cell types and reagent and instrument costs. Adding to the mix is the choice of dispensing technology. Bulk liquid dispensing generally uses either peristaltic pump or syringe pump technologies.

Peristaltic pump dispensers

Peristaltic pump technology uses flexible tubing and rollers fixed to a rotating rotor. As the rotor revolves, the tubing containing fluid is compressed where it meets the rollers, thus forcing out a measured liquid dose. The volume is dependent on, and controlled by, the distance between the rollers, tubing tension and internal diameter and dispenser tip geometry.

Flexible and autoclavable tubing ensures that the fluid path is fully contained and completely sterilizable, and multiple channels dispense a wide variety of chemicals without risk of cross-contamination or tubing compatibility issues. Precious reagents and cells benefit from low dead and prime volumes, and may be recovered by reversing the pump's direction.

Conversely, high viscosity and micro-volumes may be problematic for peristaltic pump dispensing along with fluid dispensed in fractions rather than full volumes. Replacement tubing adds to the overall instrument cost.

Syringe dispensers

Syringe dispensers provide high accuracy and precision with long-term stability and eliminate the need for routine calibrations. Additionally, they are typically faster than peristaltic pump dispensers for larger volumes, there is no fluid output pulse, and the flow rate is fully controllable from low, gentle cell culture dispensing to vigorous reagent dispensing. Because syringe dispensers do not require consumables, ancillary maintenance and replacement costs are reduced or eliminated.


On the other hand, while multi-channel syringe dispensing is available, the volume range can be more limiting than that of peristaltic pump dispensers.

Each dispensing technology has advantages and limitations that could impact the assay types that can be performed. Further adding to the criteria is automation compatibility. Integrating one or more dispensers into a robotic system greatly increases throughput and efficiency, and stacking the dispensers saves valuable bench space.

A bulk dispenser offering peristaltic pump and syringe dispensing in one unit, coupled with automation and stacking compatibility, provides unlimited flexibility in assay type and increases throughput for medium-to high-throughput laboratories.

The MultiFlo Microplate Dispenser from BioTek Instruments bridges the gap between peristaltic pump and syringe bulk dispensing; combining the best of each dispensing technology and compensating for their respective weaknesses. A total of four independent reagents may be dispensed in parallel into standard microplates from 6- to 1536-well, as well as low-profile and deep-well microplates and microtubes. A fully modular and upgradable design allows for dispensing from 1 uL to 3 mL with one or two full-volume peristaltic pumps, two syringe pumps or any combination thereof. Users can buy only what is needed now and purchase additional reagent channels in the future when assay requirements change.

Proprietary angled dispensing ensures compatibility with all dispense protocols from gentle treatment of loosely adherent cell monolayers to rigorous or viscous reagent additions. Robotic integration and stackability are simple, and the dispenser may be programmed via the keypad interface or PC software.

By combining dispensing technologies and multiple reagents, the MultiFlo increases assay flexibility and eliminates multiple manual plate movements using less bench space than separate dedicated dispensing instruments.

At a glance

* Level, performance, sterility, maintainence and cost are just a few factors to consider when selecting pump technlogies.

* Peristaltic pump technology uses flexible tubing to ensure a fully contained fluid path.

* Syringe dispensers eliminate the need for routine calibrations.

* Combining technologies increases assay flexibility and eliminates multiple manual plate movements.


For additional information on the company discussed in this article, see Laboratory Equipment magazine online at or the following Web site:

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Title Annotation:Emerging Technologies in Life Science & Biomedical Labs
Publication:Laboratory Equipment
Date:Feb 1, 2011
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