Underfilling (revision 3)
Old revision·20:24, 20 Nov 2024·Ref_Desk_Ron
| Underfilling | |
|---|---|
| Failure | Delivered mass below nominal |
| Not detected by | Purity determination |
| Detected by | Gravimetric fill check, or content with fill mass |
| Topic infobox · conventions | |
Underfilling is the delivery of less material in a container than the quantity stated on its label. It is a distinct failure from impurity and is invisible to the determination most often supplied: area percent purity is normalised and does not change with the amount of material present.[1]
The quantity a purchaser cares about is the mass of peptide in the vial. That is the product of three things — the fill mass, the peptide content of the solid, and the purity — and a certificate reporting only the last of these constrains it hardly at all.[1]
Why purity does not detect it
[edit]Chromatographic purity is computed as the area of the main peak divided by the total integrated area, expressed as a percentage. Both terms scale with the amount injected, so the ratio is invariant to concentration over the linear range of the detector.[2]
A consequence is that a half-filled vial and a correctly filled vial of the same material give the same purity figure. The determination is answering a question about composition, and fill is a question about quantity.