Highly sensitive spectrophotometric methods for selected metals, based upon the formation of a ternary complex on a micelle surface formed in the presence of a cationic, anionic or non-ionic dispersant, are proposed. The conditions under which microgram amounts of Iron, Germanium and Tin are determined, the influence of diverse ions, the composition of the complex and the role of surfactants thereon of such complexes are examined and discussed. The initial impetus to study such metals was encouraged in part by their apparent interference in the spectrophotometric determination of other ions. Attempts are thus made to modify and improve such analyses by a similar treatment, sensitivity, selectivity and reproducibility reported in each case. Limits of detection and quantitation are also presented, being of a pharmaceutical and environmental significance. The incorporation of Fluoride ion into such systems was also studied, conclusions being such that no reaction occurs in such media. Stringent pH control being necessary to avoid apparent effects.