Adduct
Definition
An ion formed by the analyte plus something else it picked up, commonly sodium or potassium. An unrecognised adduct reads as a mass that does not match the expected one, and as an impurity peak that is not an impurity.
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
Parts Per Million (ppm)
One milligram per kilogram, or one microgram per gram. Residual solvents and elemental impurities are reported this way, and mass spectrometers also quote mass accuracy in ppm, which is a different use of the same unit.
As-Received Basis
A result calculated on the material exactly as it arrived, water and counterion included. It is the honest basis for what is in the vial and reads lower than the same measurement on a dry basis.
Anhydrous Basis
A result recalculated as though the water content had been removed, using a separately measured water figure. Two certificates can disagree by several percent purely because one reports anhydrous and the other as received.
Not Detected (ND)
The analyte produced no signal distinguishable from background at the method's limit of detection. It states the limit of what was looked for, not that the substance is absent.
Not Less Than (NLT)
A one-sided specification setting a floor. Purity written as NLT 99.0% is met at 99.0 and failed at 98.9, and nothing above the floor is more compliant than anything else above it.
Not More Than (NMT)
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.
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.