Simultaneous determination of metals at trace level in a multicomponent system. Application to real samples

Voltammetry is a very suitable, versatile and rapid method for the simultaneous metal determination in complex matrices. The present work, regarding the determination of Cu, Fe, Cr, Sn, Ti, Mo and Mn, is a very interesting example of the possibility to determine single elements in real samples. 0.1 M ammonium citrate (pH 6.1 and 8.5) was employed as the supporting electrolytes. Differential pulse voltammetric (DPV) and alternating current voltammetric (ACV) measurements were carried out using, as working electrode, a stationary mercury electrode, as auxiliary a platinum electrode and as reference an Ag/AgCl, KCl sat. electrode. The analytical procedure was verified by the analysis of standard reference materials such as Stainless Steel (AISI 321) NBS-SRM 121d1 and Highly Alloyed Steel Eurostandard 281-1a. Precision and accuracy, expressed as relative standard deviation and relative error, respectively, were of the order of 3–5%, while the detection limit for each element was around 10−9M. The standard addition technique extends the usefulness of the voltammetric method to very high element concentration ratios.