AUTOMATED VOLTAMMETRIC SYSTEM FOR SHIPBOARD DETERMINATION OF METAL SPECIATION IN SEA-WATER

An automated and semi-intelligent voltammetric system is described for trace metal analysis. The system consists of a voltammeter interfaced with a personal computer, a sample changer, 2 peristaltic pumps, a mo tor burette and a hanging mercury drop electrode. The system carries o ut fully automatically approximately 5 metal determinations per hour ( including at least 3 repetitive scans and calibration by standard addi tion) at trace levels encountered in clean sea water. The computer pro gram decides what level of standard addition to use and evaluates the data prior to switching to the next sample. Alternatively, the system can be used to carry out complexing ligand titrations with copper whil st recording the labile copper concentration; in this mode up to 8 ful l titrations are carried out per day. Depth profiles for chromium spec iation in the Mediterranean Sea and a profile for copper complexing li gand concentrations in the North Atlantic Ocean measured on board-ship with the system are presented. The chromium speciation was determined using a new method to differentiate between Cr(In) and Cr(VI) utilizi ng adsorption of Cr(III) on silica particles.