SEQUENTIAL FLOW-ANALYSIS COUPLED WITH ACSV FOR ONLINE MONITORING OF COBALT IN THE MARINE-ENVIRONMENT

The development of a compact instrument for on-line measurement of tra ce metals in seawater is described. The system is based on adsorptive cathodic stripping voltammetry (ACSV), and on the concept of sequentia l flow analysis, to perform on-line measurements with controlled pertu rbation of natural equilibria of the element. The design combines a lo w volume flow cell with a miniature solenoid pump and valves to achiev e low power consumption. The flow segmentation is time-controlled and the detection step takes place in a well-defined part of the flow stre am where reagent and sample occur mixed. The system was tested on the determination of cobalt in seawater but it is likely that the same tec hnique can be used to determine other metals detectable by CSV. The de termination range was 6-1050 pmol/L cobalt with a detection limit (30) of 6 pmol/L. The measurement rate was about 60 h(-1). Comparative mea surements were carried out using continuous flow analysis. The apparat us was used continuously on board a ship to determine the distribution pattern of cobalt in surface waters off the coast of California.