When to use plastic tubes tips and plates

Plastic tubes, tips and plates are the right vessel when the experiment needs a clean single-use surface, a shape a rotor or a reader accepts, or a sterile field you do not want to rebuild from washed glass. They are the wrong vessel when the solvent dissolves them, when the volume must be a calibrated glass volume, or when heat will warp them. This page is that choice. The glass side of the same decision is choosing laboratory glassware.

Formats sit in the laboratory plasticware catalogue. When the answer is glass, use the laboratory glassware and volumetric glassware catalogues instead of forcing a polymer. Specifications go through the quote request.

The job the polymer has to survive

List the stresses before you list the catalogue. Solvent. Temperature. Spin speed. Optical clarity. Binding of a scarce analyte. A sterile claim. A footprint an instrument already owns. A tube that satisfies the rotor and fails the solvent is still a failed tube. A plate that is beautiful and the wrong skirt for the gripper is a plate you cannot run.

Plastic is not one material. Treating "plasticware" as a chemical class is how chloroform ends up in a polystyrene reservoir and how a quantitative transfer is attempted in a tube whose graduations were moulded as a hint.

Materials as classes

Polypropylene is the default for many microcentrifuge tubes and pipette tips. It is tough, often autoclavable when the product says so, and resistant to a wide range of aqueous buffers. It still binds some proteins and nucleic acids, it can be softened by certain solvents, and it is not a volumetric flask. Low-binding and low-retention versions change the surface. They are worth the specification when the analyte is dilute. They are not magic for every buffer.

Polystyrene is clear and is the usual material of Petri dishes and many cell-culture and assay plates. Tissue-culture treatment makes the surface wettable so many mammalian cells attach. Untreated polystyrene is the choice when you do not want that attachment. Polystyrene is a poor home for many organic solvents. It also softens at temperatures polypropylene would still tolerate. Do not autoclave a plate because the tube next to it was polypropylene.

Polyethylene appears as bottles, wash bottles and some caps. High-density and low-density grades differ. Caps matter as much as tubes: a cap liner that fails in phenol is the leak, even when the tube wall survives. Polycarbonate is tough and clear and has its own solvent list. Fluoropolymers such as PTFE resist chemicals that attack the others and cost enough that they are a specified choice, not a default tip.

Glass remains the vessel when you need a ground volumetric mark, a flame or a hot plate, or a solvent on the wrong side of the polymer chart. Borosilicate does not bind a scarce DNA the way some tubes do, and it does not leach plasticisers. It breaks, and it is the wrong sterile single-use flask. The choice is allowed to be mixed inside one method: dissolve a standard in volumetric glass, then aliquot it into certified tubes.

Tips, tubes and plates

Tips are a metering surface, not an accessory. The tip must seat on that pipette. A poor seal drips and destroys the air cushion the pipette uses to measure. Filter tips add a barrier so aerosols drawn toward the barrel are less likely to leave it later. Use them when the next sample would be ruined by that aerosol, including nucleic-acid setup. Non-filter tips are appropriate for many chemical transfers. Sterile, nuclease-free and pyrogen-free are different test claims. Buy the claim you will write in the method. A rack that was poked by a dusty hand is no longer the interior the claim described, even if the box still says the word.

Tubes cover microcentrifuge tubes, conical centrifuge tubes, cryovials and PCR tubes. Thin-wall PCR tubes exist so a thermal block can change the liquid temperature. A thick storage tube in a cycler is a different reaction. Conical tubes for a swinging-bucket rotor need the speed rating and the chemical rating. Screw caps and flip caps fail differently. A flip cap that pops in a warm water bath is an open tube.

Plates differ by well number, well shape, colour and skirt. Flat bottoms suit optical reading and adherent cells. Round and V bottoms suit pellets and some mixing. Black plates cut crosstalk in fluorescence. White plates support luminescence. Clear plates let you see the cells and also let light through. A 96-well plate and a 384-well plate are not interchangeable by wishing the pipette to be careful. Skirt and height decide whether a robotic gripper or a thermocycler lid will accept the plate. Tissue-culture treatment belongs only on the culture step. An assay plate does not need it, and the treatment can change binding.

Compatibility, in decisions rather than a copied chart

No table on a webpage replaces the compatibility note for the resin in your hand. When the note is silent and the solvent is aggressive, use glass. NIST calibration procedures are the public doorway for volume as a metrology problem. A moulded line on a conical tube is not in that category.

Culture-plastic expectations for collection cell lines are described in ATCC culture guides. They do not convert an untreated plate into a growth surface.

Failure modes

Solvent attack looks like cloudiness, cracking, or a swollen cap that will not open. Adsorptive loss looks like a perfect blank and a sample that vanished at low concentration. A recovery spike into the same tube plastic tells you which failure you have. Warped plates rock in a reader and invent optical scatter. Reused "washed" tips carry over enzyme and DNA. Static makes small volumes cling to a tip and then jump to a glove. That is a delivery error, not a shy meniscus.

Leachables from some plastics inhibit enzymes or add a mass-spectrometry background. If a blank in a new tube brand grows peaks, the tube is a reagent. Name it in the method record.

Safety

Broken plastic is less likely to cut than broken glass and more likely to be thrown into the wrong waste because it "looks clean". Tips that touched a culture or a toxic chemical are the waste your assessment named. A biosafety cabinet does not make an open tip box sterile again after it has sat in the draught of the sash. Filter tips do not replace that discipline. Decontamination of reusable racks follows institutional rules. The WHO laboratory biosafety manual is a reference for that judgement, not a waste procedure printed here. This page is not medical advice.

Heat, humidity and static

In a hot laboratory, plates and tip racks left in sunlight warp, and adhesive films fail. Store them as the note says, not on the window side of the incubator. Humidity changes static: a dry, heavily air-conditioned room makes tips cling and droplets creep; a monsoon week puts condensate on cold plates brought out of a refrigerator. Wipe and equilibrate before you read an optical plate, or the fog is your signal. A power cut that warms a cold room is a reason to check whether a kit's plastic and reagents were still inside their storage range before the next run. Do not assume a sealed pouch enjoyed the outage.

What to send with an enquiry

State resin, volume, sterile or nuclease claim, filter or non-filter tips, centrifuge rating, plate colour, well shape, tissue-culture treatment and instrument fit. Ask for those words on the specification. Use the laboratory plasticware catalogue and the quote request. If the honest answer is calibrated glass, say that, and point the enquiry at volumetric ware instead of asking a tube to pretend.