number of theoretical plates (chromatography) number of theoretical plates by peak width at half height (JP14) number of theoretical plates by peak width at half height (JP14) Japanese Pharmacopeia previously required use of a different constant value to the one currently used in alignment with European Pharmacopeia for the square of the standard deviation in this method. This term represents results calculated using that alternate constant value. The number of theoretical plates calculated based on the peak width measured at half height, adjusted to use 5.55 as the square of the standard deviation in accordance with JP14. [Allotrope] number of theoretical plates by JP14 method