AssayIndex
Chromatography

Valley

The minimum of the detector signal between two adjacent peaks. Valley height relative to the smaller peak determines whether the two can be reliably integrated separately.

Related terms

Resolution (R)
Separation between two peaks: R = 2(t₂ − t₁)/(w₁ + w₂). R = 1.5 is baseline resolution. The index computes and reports R to the nearest named impurity on every record that has one, and applies no acceptance criterion to it — resolution to whichever impurity happens to elute closest is a property of the compound and the gradient, not a system-suitability requirement.
Shoulder
An unresolved peak appearing as an asymmetric bulge on the leading or trailing edge of a larger peak. The main source of integration ambiguity, and the reason the index asks for the integration convention rather than setting a resolution threshold.

Where this term appears

The glossary exists to make record pages readable without a chemistry degree. Every technical term on a report resolves here.