Determination of cobalt and iron in estuarine and coastal waters using flow injection with chemiluminescence detection

Flow injection with chemiluminescence detection (FI-CL) was used to determi ne cobalt and iron in estuarine and coastal waters. Cobalt(II) was determin ed by means of a pyrogallol-hydrogen peroxide-sodium hydroxide reaction in the presence of methanol and the surfactant cetyltrimethylammonium bromide (CTAB). With pyrogallol, the sensitivity was enhanced compared with the tra ditional reagent, gallic acid. The practical limit of detection in sea-wate r was 5 pM (3s) and there was good agreement with certified values for the sea-water CRMs NASS-5 (0.16 +/- 0.01 nM), CASS-3 (0.60 +/- 0.09 nM) and SLE W-2 (0.93 +/- 0.13 nM). Results for an Irish Sea sample gave good agreement with data obtained using cathodic stripping voltammetry. Iron(II + III) wa s determined using a luminol reaction with dissolved oxygen as the oxidant. The practical limit of detection was 40 pM (3s) and results from shipboard analysis of the CRM NASS-4 (1.95 +/- 0.14 nM) were in good agreement with the certified value (1.88 +/- 0.29 nM). Field evaluation of the instrumenta tion and analytical methods was achieved through a series of local surveys in the Tamar Estuary (UK), from which environmental data are presented.