- Gel permeation chromatography (GPC)
Narrow standards have narrow molecular-weight distribution and are typically chemically different than the sample. The polydispersity is less than 1.15.
Broad standards have broad molecular-weight distribution and are usually the same polymer as the sample being analyzed. The polydispersity is more than 1.5.
Polydispersity is the ratio of weight average molecular weight (Mw) to the number average molecular weight (Mn).