Colour reactions of rare earths-chlorophosphonazo-p-SO2NH2 and cetyltrimethylammonium bromide and their applications

A highly sensitive method for the spectrophotometric determination of rare earths has been studied. The method is based on the formation of multicomponeent complexes from the colour reactions of rare earths with CPA-p-SO2NH2 and CTMAB in 0.18 M HCl-alcohol medium. The apparent molar absorption coefficient for Ce was 1.86 x 105 l . mol-1. cm-1 at 680 nm. Beer's law was obeyed in the range of 0-15 μg Ce/25 ml. A spectrophotometric method has been aplied for the determination of rare earths in samples of cast iron and aluminium alloys, using oxalic acid as the masking agent