ISO/TS 18223:2015 describes an inductively coupled plasma atomic emission spectrometric method for the determination of nickel content (mass fraction) between 20,0 % and 80,0 % in nickel alloys.
Besides alloys where nickel is the main component regarding its content level, this method may also apply to alloys in which nickel has a content as high as several other elements (Fe, Cr, Co,?) and in which the "main element" cannot be specified.