Determination of nickel and cobalt in wastewaters and seawater by constant current stripping potentiometry with nitrite enhancement of the stripping signal

Abstract

A rapid and highly sensitive method using constant current stripping potentiometry for the determination of nickel and cobalt in seawaters and industrial wastewaters has been established. The method is based on the adsorptive accumulation of nickel and cobalt in the presence of either dimethylglyoxime (DMG) or or-benzyldioxime (a-BD) prior to stripping using a constant reducing current. Nitrite is used in the stripping step for the catalytic enhancement of the stripping signal. Analytical protocols for standard solutions using DMG or a-BD show good precision (RSDs between 3 and 4% on the same film) and detection limits (30ng/L for Ni/DMG; IOng/L for Co/DMG; 9ng/L for Co/cu-BD). However, iron interferes significantly with the determination of cobalt using a-BD. With DMG, the simultaneous determination of nickel and cobalt is possible and has been developed into a protocol readily applicable to the routine determination of these metals. The analytical protocol is rapid, easy to perform and the results are in agreement with those obtained by graphite furnace atomic absorption spectrophotometry. The DMG procedure has also been optimized for the determination of cobalt alone, which has advantages for determinations at concentrations of 1 pg/L or less.

Square wave adsorptive stripping voltammetry of nickel(II) in flowing systems at a wall‐jet mercury film electrode plated in situ

“…These effects may be attributed to two factors: firstly, in ammonia buffer the electrode surface becomes partially blocked with gas bubbles, which renders the measurement difficult and/or decreases the peak current; secondly, in the presence of nitrate ions the reduction of the Ni"-DMG complex appears to follow a catalytic mechanism, involving the chemical oxidation of Nio to Ni", which is subsequently re-reduced at the electrode. A similar mechanism was already suggested by Scollary et al to the reduction of the Ni"-DMG complex in nitrite medium [25].…”

“…Constant current stripping potentiometry of nickel was also reported using DMG and a-benzyldioxime as complexing agents. Detection limits of the order of lo-'' M were obtained [18].…”

Catalytic Adsorptive Stripping Voltammetry of Cobalt in the Presence of Nitrite at an In Situ Plated Bismuth Film Electrode

“…In this system nitrite were exploited to enhance the cobalt signal. A catalytic system in the presence of nitrite was introduced and applied to cobalt determination in various matrices using HMDE and mercury film electrodes [3][4][5][6][7][8][9]. The greatest drawback of mercury electrodes is the extreme toxicity of mercury and mercury salts employed for the preparation of mercury film electrodes.…”

The new Micro‐set for Adsorptive Stripping Voltammetric Simultaneous Determination of Nickel and Cobalt Traces in Aqueous Media

“…Adsorptive stripping voltammetry has been most often utilized for trace, separate and simultaneous nickel and cobalt ions determination in various matrices as this method ensures: high sensitivity, low costs of analysis and relatively short time of measurements. For these determinations various electrodes were used to replace highly toxic mercury electrodes including: bismuth and lead film and bulk electrodes , antimony film electrodes , unmodified glassy carbon , ion exchanger‐modified carbon paste electrodes , carbon microelectrodes modified with metal film or metal microelectrode arrays .…”