Pipettes are bought by volume range, and the accuracy specification at the bottom of a range is much worse than at the top, which is what most accuracy complaints turn out to be. Beyond the single channel instruments the choices are a repeater for many identical volumes, a multichannel for plates and a controller for serological work.
An automatic pipetting machine, and when a robot is the answer
An automatic pipetting machine is worth its cost when the same plate layout runs often enough that programming pays for itself, and when the volumes are large enough to dispense reliably. Below a microlitre, accuracy falls away on most decks. The hidden costs are tips, the deck layout that has to stay fixed, and the gravimetric verification each method needs before it is trusted.
A 16 channel pipette and the plate format it serves
A 16 channel pipette is built for 384 well plates, where the channel spacing is half that of a 96 well head, so it cannot be used on the larger format without an adapter. Channel to channel variation at small volumes is what decides whether an assay works, and it is measured rather than assumed, because a plate pattern from an uneven channel reads as a biological edge effect.
pipette verification between calibrations
pipette verification is a gravimetric check at two or three volumes against a balance with enough readability for the smallest of them, and it separates a drifted instrument from a technique problem. A quality system may set a calibrated interval with records, which is what an auditor reads. An in house check takes minutes and catches the seal failures that produce most silent errors.
repeater pipette tips and the syringe that drives them
repeater pipette tips are positive displacement syringes rather than air displacement tips, which is what lets one aspiration dispense many identical volumes and why they handle viscous and volatile liquids well. The tip size sets both the dispense volume and the number of dispenses, so the choice is arithmetic against the plate. They cost more per unit than ordinary tips.
A motorized pipette and where the motor helps
A motorized pipette moves the piston under electronic control, which makes mixing, serial dilution and reverse pipetting repeatable between operators and removes the thumb strain of a long plate fill. The trade is battery life, service cost and a heavier instrument. For a laboratory whose work is a few tubes at a time, a good manual instrument is the better purchase.
A 50 ml serological pipette and the controller it needs
A 50 ml serological pipette is a single use graduated pipette used with a controller rather than a bulb at that volume, and the specification that matters is whether it is plugged, individually wrapped and sterile. Blow out graduation marks differ between makers, so reading the last millilitre correctly depends on the type. Flow rate control is what keeps a cell suspension intact.
A thermo pipette, and buying by brand
Naming a maker, as with a thermo pipette, is usually a question about service and tip compatibility rather than performance: the cone taper decides which tips seal, the service network decides the calibration interval's cost, and the spare parts availability decides the instrument's life. Mixing brands in one laboratory means stocking two tip lines, which is a real recurring cost.
racked pipette tips against a refill system
racked pipette tips are convenient and produce the most plastic; refill inserts and bulk trays cut both cost and waste at the price of a reloading step and a small contamination risk. Sterile and filtered options exist in each format. For a laboratory with a waste target, the refill route is the measurable change, and the tip itself is identical.
Questions people ask about p20 pipette
Why is my 2 microlitre addition inaccurate on a P20?
It is at the bottom of the range, where the published accuracy is much worse. Use a smaller instrument.
Can a 16 channel head be used on a 96 well plate?
Not without an adapter. The channel spacing is half that of a 96 well head.
How often does a pipette need checking?
A quick gravimetric check between formal calibrations, and a calibrated interval with records where a quality system applies.