DETERMINATION OF SUB-NANOMOLAR LEVELS OF IRON IN SEAWATER USING FLOW-INJECTION WITH CHEMILUMINESCENCE DETECTION

The development of a highly sensitive system for the shipboard determi nation of dissolved iron at the sub-nM level is presented. The techniq ue is based on a flow injection method coupled with luminol chemilumin escence detection. Dissolved Fe(II+III) levels are determined after Fe (III) reduction using sulphite and in-line matrix elimination/preconce ntration on an 8-hydroxyguinoline (8-quinolinol) chelating resin colum n. The detection limit (3s) is 40 when 1.5 ml of sample is loaded onto the column, and the relative standard deviation is 3.2% (n=5) for a 1 .0 nhl Fe sample. One analytical cycle can be completed in 3 min. The automated method proved reliable when employed on-board the RRS James Clark Ross during Autumn 1996. mapping dissolvable Fe(II+III) levels a long the Atlantic Meridional Transect from 50 degrees N to 50 degrees S. Data from vertical profiles through the upper water column are pres ented. (C) 1998 Elsevier Science B.V.