Zinc oxide is approved by the FDA for use in sunscreens. An ion chromatography (IC) method has been proposed to replace existing titration-based assays in the monograph. The Zinc Oxide content was determined using a IC system with a cation-exchange column. The determination of zinc is achieved by the formation of anionic complexes with a eluent that contains pyridine-2,6-dicarboxylic acid (PDCA), post column derivative with 4-(2-pyridylazo)resorcinol (PAR), and absorbance detection at 530 nm. The method was validated following USP guidelines and demonstrated with different sunscreens.
This technical note describes chelation concentration, a selective concentration method, coupled directly to an ion chromatograph for the determination of transition metals in complex matrices. This method, Chelation Ion Chromatography, combines analyte concentration and matrix elimination with analytical separations and sensitive detection for transition and lanthanide metals. The result is a chromatographic technique that permits trace and ultratrace determination of metals in variety of sample matrices, especially those high in alkali and alkaline earth metals.
