Sample Cups and Cuvettes: Choosing for Your Analyzer
Sample cups and cuvettes are the two consumables that sit closest to the result, and they are not interchangeable. At LabSupplies.com, the confusion we see most often is treating them as one category: a sample cup presents the specimen to the probe, while a cuvette is the vessel the instrument actually reads light through. One is a container problem; the other is an optics problem.
For both, the first question is the same and it is not price — it is which analyser has to accept it. Cup and cuvette geometry is dictated by probe travel, carousel spacing and the optical bench, so compatibility is a hard constraint before any other consideration.
Sample Cups: Geometry Is the Specification
A sample cup holds a small aliquot at the height and position the sampling probe expects. Because that position is set by the instrument, cups are stocked against named platforms — micro cups for Hitachi and Elecsys, cups for Tosoh 360 and AIA-600 II, Abbott, Beckman, Sysmex, ACE, ATAC, Architect, Envoy 500 and Pentra 400 among them. Start from the analyser name and the shortlist narrows to one or two parts.
After compatibility, the bottom profile is what changes day-to-day behaviour:
| Bottom profile | Behaviour | Use when |
|---|---|---|
| Conical | Funnels residual volume into a narrow point under the probe | Sample is scarce and you need the last microlitres |
| Flat | Sits stable and freestanding; wider liquid surface | Routine volumes, open-bench handling |
| Round | A compromise — some funnelling, good stability | General analyser use across mixed assays |
Dead Volume Is the Number That Matters
Dead volume is the liquid the probe cannot reach — the residue left below its lowest travel. It is the difference between a paediatric or difficult draw producing a result and producing a short-sample error.
Two levers reduce it. The first is cup size: the smallest cup that holds your aliquot plus probe clearance wastes the least, which is why sub-millilitre cups exist alongside 2, 4 and 8.5 mL formats. The second is the conical bottom, which concentrates what remains into the probe's path instead of spreading it across a flat base.
There is a third option when the draw itself is short. Nesting cups drop inside a 12, 13 or 16 mm primary collection tube, raising a small sample to probe height without decanting it into a separate labelled vessel — which preserves the chain of identity as well as the volume.
Tethered Caps and Evaporation
An open cup on a carousel is evaporating, and on a warm analyser deck a small aliquot concentrates measurably over a long run. Capped formats such as the Caplugs® Evergreen tethered-cap sample cups for Hitachi and Roche platforms keep the closure attached to the cup, so it cannot be dropped or swapped between samples during loading. Where samples sit on deck before aspiration, or where the run is long, this is worth specifying.
Cuvettes: Path Length and Wavelength
A cuvette is an optical component. Two specifications carry almost all the weight.
Path length is the distance light travels through the sample, and 10 mm is the standard that instrument calibrations assume. Substituting a different path length changes your absorbance readings — it is not a like-for-like swap.
Material sets the usable wavelength range, and this is where most substitution errors happen. Plastics that look identical behave completely differently in the UV:
| Material | Range | Notes |
|---|---|---|
| Polystyrene (PS) | Visible only | The economical choice; absorbs strongly in the UV |
| PMMA / methacrylate | Visible and near-UV | Extends usable range at moderate cost |
| Borosilicate glass | Visible and into the UV | Reusable; used for analyser-specific formats |
The practical failure is running a nucleic-acid or protein A260/A280 read in a polystyrene cuvette. It transmits fine in the visible range, so the cuvette looks right, and the UV numbers are simply wrong. If your read is below roughly 300 nm, confirm the material rather than assuming.
Formats then follow volume: standard square cuvettes around 4.5 mL, semi-micro at 2.5 and 2.9 mL, and micro at 1.5 mL, all with two clear sides for a single-beam read. Semi-micro and micro formats reduce the sample needed per read, which matters when the specimen is the scarce thing rather than the cuvette.
Analyser Cuvettes Are a Different Purchase
Beyond general spectrophotometry, many clinical analysers take proprietary cuvette formats that are not interchangeable with cuvettes at all in the usual sense — they arrive as reaction vessels, segments or racks matched to the instrument's optical bench.
- Hitachi analyser cuvettes in PMMA, as replacements for 902, 911, 912, 717 and 914 systems.
- Cobas Mira cuvettes, individually wrapped, and a racked format supplied as 12-place segments.
- Mindray BS cuvette segments for BS200 and BS300 analysers.
- Abbott Architect reaction vessels, and glass cuvettes for the TDx.
- MLA Electra cuvettes for 620, 650 and 750 coagulation systems, and cuvettes for ACE and Alera chemistry systems.
For these, the analyser model number is the part number. Ordering by description alone is how labs end up with a case that does not seat in the carousel.
Selecting Cups and Cuvettes
| If your constraint is… | Specify |
|---|---|
| A named analyser platform | The cup or cuvette listed for that model — check first, not last |
| Scarce or paediatric sample | Smallest compatible cup, conical bottom |
| A short draw in a primary tube | Nesting cup for 12, 13 or 16 mm tubes |
| Long runs or a warm deck | Tethered-cap cups to limit evaporation |
| A UV read below ~300 nm | Methacrylate, PMMA or glass — never polystyrene |
| Routine visible-range absorbance | Polystyrene, 10 mm path, two clear sides |
| Limited sample per read | Semi-micro (2.5–2.9 mL) or micro (1.5 mL) |
Compare every format in the sample cups and cuvettes collection.
Frequently Asked Questions
What is the difference between a sample cup and a cuvette?
A sample cup holds the specimen so the analyser's probe can aspirate it; nothing is read through it. A cuvette is an optical vessel — the instrument passes light through it to measure absorbance. A cup is a container specification, a cuvette is an optical one.
Can I use any sample cup on my analyser?
No. Cup height, diameter and bottom profile have to match the probe's travel and the carousel's spacing. Cups are stocked against named platforms for exactly this reason; start from your analyser model rather than from volume alone.
What is dead volume and why does it matter?
Dead volume is the liquid left below the probe's lowest reach, which the instrument cannot aspirate. On scarce or paediatric samples it decides whether you get a result or a short-sample error. Reduce it with the smallest compatible cup and a conical bottom.
Which cuvette material do I need for UV work?
Not polystyrene. PS absorbs strongly in the UV, so a read below roughly 300 nm — nucleic acid or protein quantification at 260 and 280 nm, for example — needs methacrylate, PMMA, or glass. The cuvettes look similar, so confirm the material rather than assuming.
Does cuvette path length matter if the volume is right?
Yes. Path length is the distance light travels through the sample and it feeds directly into the absorbance calculation. 10 mm is the standard your instrument's calibration assumes; changing it changes your readings.
What is a nesting sample cup for?
A nesting cup sits inside a primary collection tube — typically 12, 13 or 16 mm — so that a short draw is presented at the height the probe expects. It saves decanting a small sample into a separate vessel, which preserves both volume and the chain of identity.
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Tell us the analyser make and model and we will match the cup or cuvette to it. Reach out at support@labsupplies.com.
Related Guides
- Specimen Containers Guide
- Specimen Collection & Transport
- Clinical Lab Supplies Checklist
- Test Tube Materials Guide
- Tube Caps & Closures Guide
Sources and Technical References
- CMS CLIA Program — Certificate and Survey Requirements — cms.gov
- NIST Calibration Services — Traceability for Laboratory Instruments — nist.gov
— By the LabSupplies.com Technical Team