The development of a highly sensitive system for the shipboard determination of dissolved iron at the sub-nM level is
presented. The technique is based on a ¯ow injection method coupled with luminol chemiluminescence detection. Dissolved
Fe(IIIII) levels are determined after Fe(III) reduction using sulphite and in-line matrix elimination/preconcentration on an 8hydroxyquinoline
(8-quinolinol) chelating resin column. The detection limit (3s) is 40 pM when 1.5 ml of sample is loaded
onto the column, and the relative standard deviation is 3.2% (n5) for a 1.0 nM 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(IIIII) levels along the Atlantic Meridional Transect from 508Nto508S. Data from
vertical pro®les through the upper water column are presented