Charge State
Definition
How many charges an ion carries in the mass spectrometer. Peptides commonly appear in several at once, and the series of peaks they produce is what allows the true molecular mass to be calculated.
In more detail
The charge state is how many charges an ion carries. The spacing between adjacent peaks in the series is what reveals it, and once the charge of one peak is known the molecular mass follows from arithmetic.
The series is information rather than noise. A second, unrelated series in the same spectrum is a second compound, and recognising that is often how an impurity is spotted that the chromatogram presented as part of the main peak.
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
Deconvolution
The arithmetic that turns a series of multiply-charged peaks back into one molecular mass. It is the step between what the instrument recorded and the single number printed on a certificate.
Adduct
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.
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.