Trace-metal analysis in hydroponic solutions

Abstract

A wall-jet ring–disc electrode detector has been developed for the direct on-line monitoring of the trace metals manganese, zinc and copper at the micro- and submicro-molar level in hydroponic nutrient solutions. The technique employed is of anodic or cathodic stripping voltammetry with collection (a.s.v.w.c. or c.s.v.w.c.) at ring–disc electrodes. All three elements may be quantitatively determined by a.s.v.w.c. using in situ-plated thinmercury-film electrodes. Interference effects and intermetallic compound formation are discussed. It is shown that manganese may be quantified alternatively by c.s.v.w.c. via its deposition as MnO₂. Results in test solutions and in nutrient solution agree well with theoretical predictions and the reproducibility is good. A method for determining the toxic trace-metal nickel by a.s.v.w.c. is also developed.