Not More Than (NMT)
Definition
A one-sided specification setting a ceiling, used for things wanted low: single impurities, water content, residual solvents, endotoxin. The pair NLT and NMT is how most certificates express a range.
What this means for research sourcing
Purity and identity verification are central to research reproducibility. Every Volta compound ships with >99% HPLC-verified purity and a certificate of analysis.
Related Terms in Quality
Specification
The full set of tests and acceptance criteria a material must meet to be released, agreed before manufacture. A certificate reports results; the specification is what makes those results a pass or a fail.
Lot Number
The identifier tying material in a container to the records of how it was made and tested. It is the one field that lets a vial in somebody's hand be matched to the certificate that describes it.
Sample Identification
The unique reference a laboratory assigns to what it received, distinct from the lot number the supplier assigned. A certificate carrying both is traceable from the vial to the bench and back.
Pooled Sample
Material combined from several containers and tested as one. It reports the average and hides variation between them, so a pooled result says less about any individual vial than its purity figure suggests.
Chain of Custody
The documented record of who held a sample, when, and in what condition, from collection to analysis. Without it a result describes a sample whose history cannot be shown, which matters most when the result is disputed.
Audit Trail
The instrument's own tamper-evident log of acquisitions, reprocessing and deletions, with the user and timestamp attached. It is what distinguishes a reported result from the only result obtained.
Decision Rule
The stated convention for how measurement uncertainty is taken into account when calling a result a pass or a fail. Simple acceptance ignores it; a guarded rule requires the result to clear the limit by a margin.
Guard Band
The margin a decision rule holds back from a specification limit to absorb measurement uncertainty. It makes a false pass less likely at the cost of failing material that may in fact conform.