A polymeric chelate based on salicylidene-o-aminophenol (SAP) chelating with zinc (Zn(II)) ion was studied by several spectroscopic techniques. A simple, rapid and sensitive method for the spectrophotometric determination of trace amounts of Zn(II) ion in solution by chelating with SAP is proposed. This method has been applied successfully to the determination of Zn(II) ion in Immu-C sachets samples (mg/g). The proposed method is in excellent agreement with the determination of Zn(II) ion by atomic absorption spectrometry.