An ion chromatography (IC) method has been proposed for addition to General Chapter &lt;591&gt;, Zinc Determination. It will replace existing titration-based assays in several zinc-containing drug monographs. Zinc oxide is one of the active ingredients approved by the U.S. Food and Drug Administration (FDA) for use in sunscreens. This presentation shows development of an IC method for the assay of zinc oxide in sunscreen based on the General Chapter &lt;591&gt;.  Using Dionex IonPac CS5A column with pyridine-2,6-dicarboxylate (PDCA) as  a eluent and 4-(2-pyridylazo) resorcinol) (PAR) as a post column reagent, zinc is separated from transition metals and quantified using  absorbance detection at 530 nm. Sample preparation was tailored to the sunscreen composition. The method was used to determine the zinc oxide contents of 4 suncreen preparations and validated following the guidelines outlined in USP General Chapter &lt;1225&gt;, Validation of Compendial Methods.  The method is linear ranging from 0.1 to 30 mg/mL (r<sup>2</sup>=0.9995), accurate (96-101% of label), precise (RSD=0.3-1.4%), and robust for the determination of zinc oxide in sunscreen lotions.

Determination of zinc oxide in sunscreen using ion chromatography with visible absorbance detection

256th National Meeting (2018)

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