A pipette is bought for a volume range rather than for a laboratory, and most accuracy complaints are a volume used at the bottom of a range or a tip that does not seal on that model. The other half of the cost is consumable: tips, reservoirs and the racks they come in, ordered for years rather than once.
automatic pipettes, and what the word is doing
In a catalogue automatic pipettes may mean an electronic hand pipette with a motorised piston, a repeating dispenser, or a bench robot, and the three differ by an order of magnitude in price. The electronic hand pipette earns its cost where a long plate fill causes strain or where mixing steps have to be identical between operators. A stated cycle count per charge, and battery availability years later, decide ownership.
A motorized pipette controller for serological pipettes
A motorized pipette controller replaces a rubber bulb on a serological pipette, drawing and dispensing under a thumbwheel, and the specifications that matter are the flow rate range, whether it will run while charging, and the filter that protects the motor from aspirated liquid. A controller that cannot slow down will foam a protein solution and spray a cell suspension over the hood.
A pipet tip and the seal it has to make
A pipet tip is matched to the pipette model, because the seal is made on a cone whose taper differs between makers, and a universal tip that almost fits leaks air and under-delivers without any visible fault. Filtered tips protect the piston from aerosols and are the default for anything amplified. For low volume work a low retention surface changes recovery measurably.
automated pipette tips and the deck they belong to
automated pipette tips are made for a specific robot head and are specified by rack format, tip capacity, conductivity for liquid level sensing and whether they are sterile or filtered. Rack footprint has to match the deck, and a mixed rack height stops a run. Because a robot consumes tips faster than any hand pipette, the cost per tip and the supply lead time are what the method's running cost turns on.
A multi channel repeater pipette for plate work
A multi channel repeater pipette combines several channels with a positive displacement syringe so one aspiration fills many wells, which is how a plate is dispensed without returning to the reservoir. The specification to compare is the number of dispenses per syringe at the volume actually used, and the channel to channel variation, since a plate edge effect is often an uneven channel rather than biology.
A reagent reservoir for multichannel pipettes, and the dead volume in it
A reagent reservoir for multichannel pipettes is judged by its dead volume and its shape: a stepped or V-bottomed reservoir lets the last millilitres be reached, a flat one leaves expensive reagent behind. Disposable reservoirs avoid a cleaning step that would otherwise cross contaminate a plate series. Where the reagent is scarce, a reservoir that wastes two millilitres a plate costs more than the reservoirs do.
A p20 pipette and the range it is honest in
A p20 pipette covers roughly two to twenty microlitres and is the workhorse for reaction setup, and its accuracy specification is much worse at the bottom of that range than at the top, which is why a two microlitre addition is better made with a smaller instrument. Manufacturers publish accuracy and precision per volume, and that table rather than the name is what a method should be designed against.
pipette verification, and how often it is really needed
pipette verification is a gravimetric check against a balance at stated volumes, and it separates a drifted instrument from a technique problem before either is blamed. Quarterly is common practice and quality systems may require a calibrated interval with records, which is the part an auditor reads. A quick in house check between formal calibrations costs minutes and catches the seal failures that produce most silent errors.
Questions people ask about pipets
Why is my two microlitre addition inaccurate?
Because it sits at the bottom of a twenty microlitre range. Use a smaller pipette, or check the published accuracy at that volume.
Do tips have to match the pipette brand?
They have to match the cone taper. A tip that almost fits leaks air and under-delivers with no visible fault.
How often should pipettes be verified?
Quarterly is common practice. A quality system may set a calibrated interval with records, and that interval is what an auditor checks.