Fluorescence Techniques in the Microdetermination of Metals in Biological Materials. Utility of 2, 4-Bis- N , N ´-di-(carboxymethyl)aminomethyl Fluorescein in the Fluorometric Estimation of Al +3 , Alkaline Earths, Co +2 , Cu +2 , Ni +2 , and Zn +2 in Micromolar Concentrations.