A spectrochemical method has been developed for the determination of potassium in graphite covering the concentration range between 0.1 and 10%. After wet combustion of about a 100-mg sample, potassium could be analyzed by x-ray fluorescence spectrometry with a standard deviation <1% (rel.).
F. J. Haftka, "The Determination of Potassium in Graphite by X-ray Fluorescence Spectrometry," Appl. Spectrosc. 26, 467-469 (1972)