Eliminating spectral interferences during icp-oes analysis of platinum group elements by modified tellurium collection method

Suvashis Sarkar, Aditya Lodh, Preksha Patel, S. K. Yadav

Abstract


Catalytic Converters contain a multitude of base metals and transition metals including platinum group elements (PGE).  Accurate determination of PGE’s in the catalyst is challenging owing to the wide multitude of matrix components which may interfere in the determination.  Balaram V1 detailed various methods of determination of elemental concentration of PGE’s like wet chemical acid digestions, fire assay methods –Pb and NiS collection, chlorination, slurry nebulization, alkali fusion among other methods.  For a complete sample dissolution a sequence of acid digestions (sequence of perchloric acid, nitric acid, hydrofluoric acid and finally hydrochloric acid) are found effective followed by ICP OES analysis as per Peugeot Standard D40503502.  However in the existing method of ICP analysis, we come across a wide variety of spectral overlaps of preferred wavelengths of platinum (Pt), palladium (Pd) and rhodium (Rh). 

The spectral overlaps can be corrected by Inter Element Correction (IEC) or using a variety of background editing options, like sloping background correction, curved background correction7, fitted background correction8, background (left /right/ left-right) or using curve fitting technique9. But the major disadvantage of all such steps is that it has to be reviewed each time for different matrix samples.  Hence it is needed to eliminate these spectral interferences to precisely quantify the peak areas at the specific wavelengths without the need for further corrections.

The use of tellurium co-precipitation with tin chloride (SnCl4)in the determination of PGE after nickel sulphide fire assay (NiS-FA) in geological samples was reported by Morcelli et al2.  However, there were still several aspects of the NiS-FA which were not understood and affecting the recovery of PGEs

The current method focusses on the collection of PGE from the acid digested catalyst mixture in the presence of reductants like sodium borohydride (NaBH4) and SnCl4 and their combined effect on the PGE recovery during analysis.


Keywords


ICP-OES, Te co-precipitation, reducing agents, tin chloride, sodium borohydride

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SARKAR ET AL 2022

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