Continuous shipboard determination of Fe(II) in polar waters using flow injection analysis with chemiluminescence detection

A method for the continuous underway determination of Fe(II) in polar waters is reported. Surface seawater is pumped into a shipboard clean room container using a towed fish with Teflon diaphragm pump. Fe(II) was determined by flow injection analysis using a modified FeLume. The seawater is filtered in-line and the sample containing Fe(II) is mixed with luminol (buffered to pH 10) inside a flow cell and the resulting luminescence signal measured by a Hamamatsu HC-135 photon counter linked to a laptop computer. No preconcentration of the samples was applied, to reduce possible interferences and increase the sampling frequency. The system was utilised during EISENEX, a meso-scale iron enrichment experiment sample in the Atlantic sector of the Southern Ocean. In EISENEX, when surveying the iron enriched patch, a sample was analysed every 110 s (60 s loading time and 50 s for analysis). The detection limit, as determined by analysis of seawater (maintained at 4 degreesC to minimise oxidation) spiked with known concentrations of Fe(II), ranged from 25 to 133 pM. The system was also applied to vertical profiles of Fe(II) during EISENEX. (C) 2002 Elsevier Science B.V. All rights reserved.