What do cartridge capacity, graduation and
repeatability actually mean?

Cartridge capacity,
graduation and dispensing repeatability are different device
attributes. Capacity is the declared amount the container is designed
to hold; graduation or resolution concerns the indicated step size;
repeatability describes agreement between repeated measured outputs
under defined conditions. None of those terms, by itself, proves
accuracy, trueness or a calibrated delivered quantity.

For controlled
laboratory use, start by defining the quantity that matters to the
experiment, then decide whether the manufacturer’s specification is
sufficient or whether the laboratory needs an independent
verification. Do not use “precision dosing” language: this page
concerns metrology of laboratory dispensing, not administration.

Figure
1. Illustrative metrology framework for pen cartridge and dispensing
claims.

Alt
text: Six-card metrology framework distinguishing nominal capacity,
graduation or resolution, repeatability, bias or trueness,
measurement uncertainty, and calibration versus verification.

From Our Work: specifications and analytical
evidence answer different questions

Core Research
reviews batch evidence as a connected set rather than accepting one
headline number in isolation. The approved review set can include
product and batch match, HPLC purity, MS identity, appearance,
labelled amount or content, applicable water or moisture and
counter-ion information, document completeness, and storage or
handling status. The analytical testing itself is produced by the
manufacturer and/or third-party laboratories; Core Research reviews
that evidence. When a meaningful mismatch is identified, the batch is
held while clarification and/or a justified retest is requested. This
workflow does not imply in-house analytical testing or any laboratory
accreditation claim.

The same separation
applies to device claims. A batch CoA may support the peptide
evidence, while a cartridge capacity or graduation statement is a
device specification. If a method depends on delivered quantity or
repeatability, that device characteristic should be supported by the
manufacturer’s documented specification or by a defined laboratory
verification; it should not be inferred from HPLC purity, MS identity
or nominal fill alone.

What is nominal cartridge capacity?

Nominal capacity is
a declared design quantity for the container. It should not be
silently converted into “usable delivered volume” because
residual volume, dead space, the fluid path and mechanical limits can
affect what can actually be transferred. When usable volume matters,
define the measurement procedure rather than calculating it from
capacity alone.

What is graduation or resolution?

The VIM defines
resolution as the smallest change in a quantity being measured that
causes a perceptible change in the corresponding indication. Applied
to a dial or graduation, the displayed increment is therefore a
resolution-like property; it is not a proof of accuracy. A device can
show fine increments while still having bias, variability or
operating-condition effects that need separate assessment.

What is dispensing repeatability?

Repeatability
concerns how closely repeated measurement results agree under defined
repeatability conditions — for example, the same device, procedure,
operator and operating conditions over a short period. A useful
repeatability check records the defined setting, measurement
procedure, number of replicates and the observed spread. The result
should be reported as measured data, not collapsed into a marketing
adjective.

Is repeatability the same as accuracy?

No. A device can
produce highly clustered repeated outputs that are all systematically
offset from a reference value. That is good repeatability with bias.
Conversely, a device can average near a reference while individual
outputs vary too widely. For method suitability, ask separately about
repeatability, bias or trueness, resolution and measurement
uncertainty.

When can a laboratory call the device calibrated?

Use “calibrated”
carefully. Under the VIM, calibration establishes a relationship
between indications and values provided by measurement standards,
with associated measurement uncertainties. It is not the same as
adjustment, a mechanical zero check or a simple pass/fail
verification. If the laboratory has only checked that repeated
outputs meet an internal acceptance rule, describe the activity as
verification unless a real calibration relationship was established.

How should dispensing performance be verified for
an in-vitro method?

1. Define the measurand: for
   example, delivered mass or volume under the laboratory’s chosen
   method.

2. Define the device setting(s),
   fluid or surrogate, operating conditions and replicate plan.

3. Use a suitable reference
   measurement system and record its calibration/uncertainty status
   where relevant.

4. Measure repeatability
   separately from any systematic difference from the reference.

5. State the acceptance criterion
   before testing, based on the experimental need rather than a generic
   internet threshold.

6. Record device ID,
   cartridge/interface configuration and any maintenance or adjustment
   performed.

7. Re-check after a relevant
   device change, damage event or other condition that could reasonably
   affect performance.

What should not be inferred from a fine
graduation?

A fine graduation
does not establish exact usable capacity, low dead volume, low bias,
high repeatability or suitability for every liquid. Fluid viscosity,
interface geometry, friction, device wear and measurement procedure
can all influence results. The correct claim is the narrow one the
evidence supports.

Frequently asked questions

Is a smaller dial increment automatically more
accurate?

No. A smaller
increment improves displayed resolution, but measurement accuracy
also depends on bias, repeatability, the measurement method,
reference and operating conditions.

What is the difference between repeatability and
reproducibility?

Repeatability keeps
conditions tightly controlled; reproducibility considers results
under changed conditions such as different operators, locations or
measuring systems. Use the term that matches the test design.

Can I call a mechanical zero check a calibration?

Not by itself. A
zero or readiness check can be part of device preparation, but
calibration is a metrological operation involving reference values
and uncertainty.

Does nominal cartridge capacity equal usable
volume?

Not necessarily.
Capacity is a design specification. If usable delivered volume
matters to the experiment, measure it using a defined method rather
than assuming it equals the nominal value.

Does this page provide dose calculations?

No. It covers
laboratory device measurement concepts only. For in-vitro
concentration and dilution arithmetic, use the dedicated
molecular-mass, molarity and dilution guide.

Key takeaway

Keep the claims
separate: capacity is not usable volume, graduation is not accuracy,
repeatability is not trueness, and verification is not automatically
calibration. Define the measurand and evidence needed for the
laboratory method before accepting a device-performance claim.

References

[1] JCGM 200:2012
International Vocabulary of Metrology (VIM3). BIPM / JCGM.
Accessed 14 August 2026. Source.
Defines calibration, verification, repeatability, resolution,
measurement error and uncertainty; used here for metrology
terminology.

[2] NIST/SEMATECH
Engineering Statistics Handbook, Chapter 2: Measurement Process
Characterization. NIST. Accessed 14 August 2026. Source.
Used for repeatability, reproducibility, stability, measurement
control, calibration and uncertainty concepts.

[3] ISO
11608-1:2022, including Amendment 1:2026 — Needle-based injection
systems, Part 1. ISO. Accessed 14 August 2026. Source.
Engineering reference for device performance concepts only.
Core Research does not claim that its RUO devices are certified to,
or legally governed by, this medical-use standard.

[4] ISO
11608-3:2022, including Amendment 1:2026 — Containers and
integrated fluid paths. ISO. Accessed 14 August 2026. Source.
Engineering reference showing that containers and integrated fluid
paths require their own design verification; used conceptually, not
as a regulatory claim for RUO products.