BUNSEN

Author: BUNSEN

  • 96-Well PCR Plates & 8-Strips: Do They Fit Your Instrument?

    Two plates can both be labelled “96-well”, yet one returns clean amplification curves while the other shows persistent edge-well variation. Meeting the SBS footprint is the easy part — thermal and mechanical fit are what decide whether your run works.

    SBS compliance only gets you in the door

    The SBS/ANSI standard fixes the outer footprint, the 9 mm well pitch and the well positions, so almost any 96-well plate will physically drop into a plate carrier. What it does not fix is the geometry of your sample block, the clamping force of the heated lid, or how the plastic behaves at 95 °C. Those are the variables that separate a plate that merely fits from one that performs.

    Where plates actually go wrong: thermal fit

    A cycler never heats your sample directly. It heats the block, the block heats the well wall, and the wall heats the reaction — so anything that adds thermal resistance slows the ramp. The failure modes we see most often:

    • A plate that sits slightly proud of the block, leaving an air gap across part of the well.
    • A warped skirt that lifts one edge, so the heated lid seals unevenly.
    • Thin or inconsistent wall thickness, which produces well-to-well ΔT before the run even starts.

    Ask the supplier which cycler platforms the plate was actually tested on. Many consumable manufacturers validate against mainstream platforms such as ABI, Bio-Rad and Roche instruments — but “validated” should mean ramp-rate and Ct data, not just a dimension drawing.

    Wall thickness and the edge effect

    When the outer ring of wells amplifies later than the centre, the cause is usually heat loss at the plate edge rather than the master mix. Uniform wall thickness and a skirt that seats the plate squarely both help. So does a seal that contacts the whole rim surface rather than only touching the outer wells — a detail that is easy to overlook when you are choosing between films.

    Skirt style and automation

    • Skirtless — the cheapest option and fine for manual work, but it flexes inside the block.
    • Semi-skirted — the general-purpose choice: rigid enough for most cyclers and still compatible with many grippers.
    • Fully skirted — the most rigid, the best choice for robotic handlers, and the most stable when the plate doubles as a storage index.

    If a plate will move between cycler, qPCR reader and freezer, full skirt is the safer default.

    8-strip tubes: the same question at a smaller scale

    Strip tubes trade plate rigidity for flexibility. A strip that is slightly out of register sits crooked in the block, and because each tube is a separate thin wall, temperature differences between tube 1 and tube 8 are easier to see than they are across a plate. Strips are genuinely convenient when you run a handful of samples, but if you need consistent Ct across a full 96-well run, a plate is usually the better tool.

    A 20-minute qualification test before you order

    1. Give the supplier your exact cycler model and block type.
    2. Request the plate drawing and the wall-thickness tolerance.
    3. Run one pilot plate with the same dilution series in every column, outer wells included.
    4. Compare Ct of the edge wells against the centre wells. A spread beyond roughly 0.3 Ct is worth a conversation with the supplier.

    Sealing is part of the fit

    The seal changes the thermal path almost as much as the plate does. An adhesive film adds a layer between the block lid and the reaction; a foil conducts differently again; a strip cap sits only over the tubes. Whichever you choose, confirm that it is rated for the same temperature range as the plate and that it does not lift at the rim during a 40-cycle programme.

    Note: The information on the scientific research products above is for reference only!

  • Cleanliness of Lab Consumables: Which Dimensions Matter?

    In a life-science lab, “cleanliness” is almost always the first hurdle when you select single-use plastic consumables. The problem is that the words used to describe it — DNase/RNase-free, pyrogen-free, sterile, SAL — get used interchangeably in sales material even though they describe completely different levels of control, tested by different methods.

    Three claims that are usually confused

    Enzyme-free, pyrogen-free and sterile answer three separate questions: will the plastic damage my sample, will it trigger an immune response, and is anything alive on it? A product can be sterile without being endotoxin-controlled, and endotoxin-controlled without being certified nuclease-free. Read the certificate, not the product name.

    Enzyme-free and inhibitor-free

    “DNase/RNase-free, free of PCR inhibitors” applies to molecular work. Nucleic-acid experiments are extremely sensitive to nuclease contamination — a trace of DNase left on a tube wall is enough to degrade a low-copy sample during incubation, and you will see it as a failed amplification rather than as contamination. Inhibitor-free matters for the same reason: residual mould-release agents or UV stabilisers that leach into the reaction can suppress polymerase activity without any visible sign.

    Pyrogen-free means endotoxin-controlled

    Pyrogen-free (typically endotoxin below 0.1 EU/mL) targets cell culture and bioprocessing. Endotoxins are fragments of Gram-negative bacterial cell wall; they survive autoclaving, so sterility alone gives you no protection at all. In cell work they disturb growth and can shift a bioprocess result; in anything destined for a patient-facing workflow they are a release criterion rather than a nice-to-have.

    Sterile is a process — SAL is a probability

    After gamma irradiation, sterility is expressed as SAL (Sterility Assurance Level). SAL 10⁻⁶ means the theoretical probability of a non-sterile unit is no more than one in a million. That is a statistical statement about the validated process, not a guarantee about the individual item in your hand — which is exactly why the irradiation dose and the validation record matter more than the word “sterile” on the bag.

    What a batch CoA should actually show

    A professional supplier issues a Certificate of Analysis per batch, and a usable one states measured values rather than ticks:

    • Endotoxin result and the method used (LAL, kinetic or gel-clot)
    • Sterility result, irradiation dose and SAL claim
    • RNase/DNase and PCR-inhibitor test result
    • Resin identity and, where relevant, USP Class VI status
    • Batch number and expiry that match the carton you received

    If the CoA is a generic template with no batch number, it tells you nothing about your shipment.

    Match the grade to the application

    Buying the highest grade for everything is as much a mistake as buying the cheapest. General sample handling needs clean, consistent plastic. PCR and sequencing need nuclease-free and inhibitor-free. Cell culture needs endotoxin control on top of sterility. IVD reagent production usually needs the full set plus a documented change-control process.

    Questions worth asking before you commit

    • Which cleanroom class is the product packed in, and is it the same class as the moulding area?
    • Is sterility achieved in-house or by a subcontract irradiator, and can you see the dose record?
    • Does the batch CoA travel with the shipment or only on request?
    • What is the actual wall-thickness tolerance, and does it change between batches?

    Cleanliness is not about what is claimed; it is about traceable test data for every single batch you receive.

    Note: The information on the scientific research products above is for reference only!

  • Welcome to the BUNSEN Blog

    This is the official blog of BUNSEN. We write about the practical side of lab consumables — how to choose them, how to use them without losing samples, and what the specifications on the certificate actually mean.

    What you will find here

    The articles fall into three rough groups:

    Where the specifications live

    Detailed drawings, capacities, RCF ratings and packaging options are on the main site at bensenbio.com, covering centrifuge tubes, PCR consumables, cell culture ware, cryogenic storage and reagent bottles. The blog does not duplicate those tables — it explains how to read them and where the common traps are.

    Who writes it

    The posts are written by the BUNSEN technical team from questions that come up in customer support and QC: fit problems reported on specific instruments, batch-to-batch variation, and handling steps that are easy to get wrong in a busy lab. If a question keeps arriving by email, it usually ends up here.

    Note: The information on the scientific research products above is for reference only!

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