Multichannel technique on a 96-well plate

A 96-well plate rewards a multichannel pipette and punishes a loose tip. The decision is whether an eight-channel or twelve-channel tool will make the wells more alike than a careful single channel, and which differences it cannot see. Single-channel forward technique, the two stops, and pre-wetting are the baseline in accurate micropipetting technique. A multichannel is that baseline repeated in parallel, plus a new set of ways for one channel to disagree with the others.

What each tool can show

A single-channel pipette shows you one tip, one well, and one stroke. You can touch a wall, chase a bubble, and reject a drip before it becomes a row. You cannot feel whether the next seven wells would have matched. It is the right instrument for standard curves that are not a full column, for viscous liquids that need a pause you can watch, and for any well that is an exception.

An eight-channel pipette aligns with the eight rows, A to H, and fills a column in one movement. A twelve-channel pipette aligns with the twelve columns and fills a row. Used on a reservoir, either one can put the same reagent across the plate quickly. What it can show, if you look, is a tip that sits higher than its neighbours, a piston that feels soft, or a reservoir corner that has run dry so the outer channels suck air. What it cannot show is a biological edge effect that appears later because outer wells evaporate during a long incubation. That stripe is the plate and the lid, not proof that channel A was calibrated differently from channel H.

ISO 8655-2:2022 includes multi-channel air-displacement and positive-displacement pipettes, complete with selected tips, and it is where maximum permissible errors for that class are specified. This page does not reproduce those tables. ISO 8655-1:2022 supplies terminology and user recommendations. A calibration sticker is not a substitute for watching the tips enter the wells together today.

Tip seating, angle, and depth

Seat all the tips with one level press. A rocking press clicks the centre tips and leaves the end tips proud. Those proud tips leak or they sit at a different immersion when you reach the plate. Hang the pipette so you can see the whole row of orifices against a light background before you aspirate. If one tip looks short, eject and reseat. Do not twist that tip on with a finger and hope the seal caught.

Hold a consistent angle. Vertical aspiration from a reservoir keeps immersion equal. A tilt that feels comfortable for your wrist lifts one end of the tip row out of a shallow reservoir and buries the other end. The high end takes air. The low end takes liquid on the outside of the tip, and that outside liquid wipes off into the well. It was never inside the calibrated stroke. Rest your elbow so the angle is a choice, not a compromise you change between column 1 and column 12.

Depth should be the same at every well. Hovering above some wells and touching the bottom of others changes delivery and can scratch a cell layer if that is what the plate holds. For aqueous forward pipetting, a touch to the wall, then the first stop, a pause, and the blow-out, matches the usual single-channel habit. Dispensing into liquid already present is a mixing choice. Standardise it. Releasing the plunger while tips are still in the wells pulls liquid back up eight or twelve at a time.

Viscous liquid is where multichannel work goes quiet and wrong. Eight tips do not finish draining together if you use a water rhythm. Slow the stroke, consider reverse pipetting, or return the viscous reagent to a single channel or a positive-displacement tool. A multichannel does not make glycerol aqueous.

Workflow and the branch when one channel lags

Pre-wet every tip if the method is aqueous or volatile. Aspirate from a reservoir that is deep enough for the whole row at a shallow immersion. Watch the liquid columns. They should rise together. A column that lags is a leak, a soft piston, or a tip against the reservoir wall. Expel and fix it before any well is filled.

Dispense across the plate in an order you can describe, usually column by column for an eight-channel tool. Keep the plate flat. A plate that rocks on a stack of lids changes depth at one end. If one channel's tips look empty early, stop. Mark that channel. Do not finish the plate and plan to "remember" which row to ignore. The branch is to move the remaining wells to a checked single channel or to a different multichannel, and to tag the faulty channel out of quantitative use until it is checked. An interim water check of each channel, in the spirit of checking a pipette between calibrations, is the right next measurement. A mean of all eight channels can hide one bad row inside an acceptable average.

Failure modes

A striped plate, one row high or low across all columns, is a channel or a tip. A plate that is fine in the centre and odd at the edges after a warm incubation may be evaporation, especially if the pipette check was clean. A plate that changes halfway across is often a reservoir that ran low, a thumb that tired and started snapping, or a switch from wall-touch to mid-air dispense. Record which columns were done after a break.

Do not calibrate only the end channels and assume the middle. The specification you claim applies to the channels you use. A laboratory gravimetric check compares those channels with that specification. NIST's Office of Weights and Measures is a public doorway into that metrology habit. It does not set your acceptance limit.

Safety

A multichannel makes eight aerosols where a single channel made one. Cultures, toxic small molecules, and volatile solvents scale with the tip count. Follow the institutional assessment, use filter tips when it asks, and keep the plate in the containment you already named. This is research technique, not a diagnostic plate layout and not clinical dosing.

What to put in an enquiry

State channel count, volume range, aqueous versus viscous liquids, filter-tip needs, and whether calibration documentation must cover every channel at the volumes you use. Browse instruments in the scientific instruments catalogue and tips, reservoirs, and plates in the laboratory consumables catalogue. Send the plate format and the tip family with the quotation request.