DETERMINATION OF ZINC IN SEAWATER USING FLOW-INJECTION ANALYSIS WITH FLUOROMETRIC DETECTION

A sensitive technique for the shipboard determination of zinc in seawater has been developed. The technique couples flow injection analysis with fluorometric detection (FIA-FL). A cation exchange column was used to separate zinc from interfering alkali and alkaline earth ions and to concentrate Zn from seawater. The organic indicator ligand, p-tosyl-8-aminoquinoline, was used to form a complex with zinc, the fluorescence of which was determined with a flow-through fluorometer. The detection limit (defined as three times the standard deviation of the blank, n = 4) was 0.1 nM for a 4.4-mL sample. The precision based on the replicate analysis of samples containing 4.3 nM Zn was +/-6% (n = 5). A single sample can be analyzed in 6 min. The technique was determined to be accurate on the basis of analysis of the standard seawater solutions CASS-2 and NASS-2 and by comparison with previous reliable investigations. A typical profile of 12 samples along with standards and blanks can be completed in triplicate in 5.5 h.