A millilitre sits at the top of the common air displacement range, where accuracy is easiest and the choice is really about how the transfer is made: by hand, under a motor, or by positive displacement for a liquid that does not behave. The consumables around the instrument matter as much as the instrument.
pipette accessories that change the result
pipette accessories are not all conveniences: a charging stand decides whether an electronic instrument is ever flat, a shelf or carousel keeps a pipette off the bench where the tip picks up contamination, and a calibration kit with a stated balance readability is what makes an in house check meaningful. Replacement seals and pistons are what keep an instrument in service rather than in a drawer.
digital pipettes and what the display is for
digital pipettes show the set volume rather than a mechanical dial, which removes misreading and, on electronic models, allows programmes for mixing and serial dilution. A display on a manual instrument changes nothing about accuracy. The useful question is whether the volume can be locked, since an accidental change is the commonest source of a silently wrong plate.
An electric pipette and where the motor pays
An electric pipette earns its cost in plate filling, in serial dilutions that have to match between operators, and where repetitive strain is a real risk, and it costs battery management and service. Aspirate and dispense speeds are settable, which matters for foaming proteins and for cell suspensions. For a few tubes a day a good manual instrument is the better instrument.
A p2 pipette and the sub microlitre problem
A p2 pipette covers a fraction of a microlitre to two, where evaporation from the tip, the wetted surface and the seal dominate the error, so the published accuracy at the bottom of the range is what the method has to live with. Where a protocol calls for half a microlitre repeatedly, a dilution and a larger transfer is nearly always the more reproducible design.
A piston pipette, and air against positive displacement
A piston pipette in the positive displacement sense has the piston inside a disposable capillary that contacts the liquid, so viscosity, volatility and density stop mattering, which is why it is used for glycerol, organic solvents and radioactive samples. An air displacement instrument is cheaper per transfer and more convenient, and it is what a laboratory uses for everything else.
A positive pressure pipette and where that phrase is used
A positive pressure pipette is the same positive displacement idea described by how it expels the liquid, pushing rather than drawing, which is what eliminates the air cushion and its dead volume. The consumable is a capillary and piston assembly rather than a tip, so the cost per transfer is higher and the choice is made per application rather than per laboratory.
A multi tip pipette for plate work
A multi tip pipette carries eight, twelve or sixteen channels at a fixed spacing matched to a plate format, and channel to channel variation at the volume actually used is the specification that decides whether an assay works. Adjustable spacing models move between tube racks and plates at the cost of weight and price. Tip loading force matters over a long session.
pipette tips material and conductive pipette tips
pipette tips material is virgin polypropylene for almost everything, with additives changing surface behaviour: a low retention surface recovers more of a detergent free sample, while conductive pipette tips carry carbon so a robot can sense the liquid level capacitively. Conductive tips are for automation rather than the bench, and they are not interchangeable with clear tips in a method.
Questions people ask about 1 ml pipette
When is positive displacement worth it?
For viscous, volatile, dense or radioactive liquids, where the air cushion in an ordinary pipette makes the volume wrong.
Are conductive tips better?
They are for robots that sense liquid level capacitively. On the bench they add nothing.
Why is a 0.5 microlitre transfer unreliable?
Evaporation, wetting and the seal dominate at that volume. Dilute and transfer more.