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Simultaneous determination of palladium and nickel in electroplating solutions by differential-pulse polarography

Simultaneous determination of palladium and nickel in electroplating solutions by differential-pulse polarography,10.1039/an9921701623,Analyst,Bharath

Simultaneous determination of palladium and nickel in electroplating solutions by differential-pulse polarography   (Citations: 2)
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Differential-pulse polarography can be successfully employed for the simultaneous determination of palladium and nickel in electroplating baths. Both palladium and nickel give peaks in ammoniacal ammonium chloride and ammoniacal ammonium tartrate media that are separated by about 250 mV. When the nickel-to-palladium ratio exceeds 100, ethylenediaminetetraacetic acid (EDTA) may be added to complex nickel and thus remove the interference due to an excess of nickel. In the presence of large amounts of palladium, dimethylglyoxime is used to enhance the peak current of nickel. The palladium peak in ammoniacal ammonium chloride buffer at pH 9.0 is not affected by the presence of either EDTA or dimethylglyoxime. Hence it is possible to determine palladium and nickel simultaneously and in the presence of an excess of each other. Electroplating baths containing various amounts of palladium and nickel are used for the deposition of certain alloy compositions. Recently, palladium-nickel alloy coatings have gained acceptance as an undercoat to reduce the thickness of gold plating in the electronics and watch industries. These alloys are used as a substitute for gold as a contact material for electronics applications. There are economical and techno- logical advantages for substituting palladium or palladium alloys for gold. 1 Economically, substantial cost reductions can be achieved owing to the lower price of palladium coupled with its lower density. Technologically, material properties of palladium such as hardness, ductility and thermal stability are superior to those of hard gold. The use of palladium-nickel alloy plating is increasing and hence it is necessary to determine the palladium and nickel contents in plating solutions, wash solutions and effluents. Both palladium and nickel form coloured complexes with dimethylglyoxime (DMG) and this has been employed for the separation of palladium from other elements,2 but as the sensitivity of the palladium-DMG complex is low, it is rarely used for its determination.3 We have found that by using differential-pulse polarography (DPP), it is possible to deter- mine palladium and nickel simultaneously and the method does not involve any tedious and time-consuming separation steps. Wild4 used a supporting electrolyte (SE) of 1 rnol dm-3 pyridine and 1 rnol dm-3 potassium chloride for the determi- nation of Pd" in nickel and palladium plating solutions. Other supporting electrolytes used are cyanide,5 ethanolamine,b glycine7 and caprolactam,g but it was not reported whether these media could be used for the simultaneous determination of nickel and palladium. Flora and Nieboerg investigated the highly sensitive peak obtained for Ni" in the presence of DMG and applied this method to the determination of Nili in lake water by DPP. Later, Torrance*() used this method for the determination of Nil1 and Co". This paper describes polaro- graphic methods for the simultaneous determination of nickel and palladium in electroplating baths, effluents and wash solutions.
Journal: Analyst , vol. 117, no. 10, 1992
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