Sequential flow analysis coupled with ACSV for on-line monitoring of cobalt in the marine environment

Abstract

The development of a compact instrument for on-line measurement of trace metals in seawater is described. The system is based on adsorptive cathodic stripping voltammetry (ACSV), and on the concept of sequential flow analysis, to perform on-line measurements with controlled perturbation of natural equilibria of the element. The design combines a low volume flow cell with a miniature solenoid pump and valves to achieve low power consumption. The flow segmentation is time-controlled and the detection step takes place in a well-defined part of the flow stream where reagent and sample occur mixed. The system was tested on the determination of cobalt in seawater but it is likely that the same technique can be used to determine other metals detectable by CSV. The determination range was 6–1050 pmol/L cobalt with a detection limit (3σ) of 6 pmol/L. The measurement rate was about 60 h–1. Comparative measurements were carried out using continuous flow analysis. The apparatus was used continuously on board a ship to determine the distribution pattern of cobalt in surface waters off the coast of California.