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Positive Displacement Pipettes

23 August 2019
Although they're not as widely used as air displacement pipettes, positive displacement pipettes offer flexibility and a host of benefits to scientists in a variety of fields

How do they work?

A disposable piston moves within the tip, making direct contact with the liquid. The piston then moves upwards, drawing the sample into the tip (No air cushion is present as with air displacement pipettes, so a physical void of the selected volume is created). The selected volume is dispensed as the piston descends.

Benefits & Uses

Positive displacement pipettes offer reduced volatile solvent evaporation and prevent cross contamination, since there’s no contact between liquid and pipette.

They are therefore highly suited to work with difficult and volatile substances where an air displacement pipette would require the air cushion to be saturated in order to prevent evaporation. They’re also less affected by atmospheric pressure or the temperature of the lab because there’s no air cushion. 

Perfect for use with:

High density solutions
Viscous solutions (like resins, fats, protein solutions and oils)
Dense solutions
Foaming liquids
Volatile liquids
Problematic liquids

Ideal for use in:

Food and beverage manufacture
Cosmetic production
Forensic Science
Molecular Biology
Environmental research 
DNA sample work and PCR

Tips & Techniques

In order to avoid errors always practice the following:

    • Choose the right pipette for your needs
    • Practice, practice, practice! Perfect your technique with help from a thorough pipetting guide. Your chosen brand will likely have one (try this one from Gilson)
    • Ensure you’re holding your pipette vertically when drawing in liquid, immersing the tip slightly so as not to coat the outside and add more liquid than you want to
    • Use a smooth, careful action and don’t rush
    • When you dispense, keep your pipette vertical but hold the vessel you’re dispensing into at a 45 degree angle
    • Test yourself – You can check the accuracy of your process by recording the mass of dispensed droplets on a fine balance and checking your variation, if it’s less that 5% you’re good to go. If not, keep going until your technique’s down and your confidence is up!
    • Look after your pipette: Get your pipette serviced regularly by a “pipette doctor” who will replace worn out parts and recalibrate for you
    • Storage: Try to always store your pipette vertically in a pipette holder rather than on its side
    • Clean your pipette every day before you start work using 70% ethanol and have a look to see if there’s any damaged parts

    We offer Microman positive displacement pipettes from Gilson in 2 sizes: The M10 (1-10ul) and the M25 (3-25ul). They offer reliable, precise and reproducible pipetting for a variety of liquid handling applications.

    Microman pipettes also offer 3 to 4 times the performance of air displacement pipettes with problem liquids (volatile or viscous substances) plus total protection from contamination. They are supplied with Gilson’s lifetime warranty, providing peace of mind, a yearly service and minimal administration should you need assistance at any other point. Your return on investment will be higher as annual costs will be reduced and your pipette will last far longer. 

    If you’d like to speak with us about your pipette requirements and discuss the Gilson Microman please get in touch.