Voltammetric determination of Zn(II) in Zn-Fe alloy electroplating baths using square-wave voltammetry

a routine analytical method for zinc (ii) determination in zn-fe alloy galvanic baths was developed employing square-wave voltammetry with the static mercury drop electrode (smde) as working electrode. real alloy bath samples were analyzed by the standard addition method and recovery tests were undertaken. the supporting electrolytes used in the analyses were 1.0 mol l-1 nh3 / 0.2 mol l-1 nh4cl or 0.1 mol l-1 citric acid (ph=3), presenting peak potentials for zinc (ii), respectively, at -1.30 v and -0.99 v vs. ag|agcl (saturated kcl). the proposed voltammetric method showed a linear response range at 25 °c between 1.0 x 10-5 and 2.2 x 10-4 mol l-1 for zinc (ii), in both electrolytes studied. the interference levels for some metals, such as cu (ii), pb (ii), cr (iii) and mn (ii), which could prejudice zn-fe alloy deposition, were evaluated. these ions did not present significant degrees of interference in the zinc (ii) determination. the zinc (ii) recovery tests for the proposed method exhibited a good agreement with the reference method, showing relative errors lower than 3.0%.