Continuous flow analysis of iron (III) in seawater using a chalcogenide glass ion-selective electrode

Continuous flow analysis (CFA) is suitable for rapid and reliable determination of free Fe^III in organic-free, UV-oxidized seawater when used in conjunction with an extrapolation method that predicts the steady-state potentials of an Fe^III chalcogenide glass ion-selective electrode (ISE) by using initial data associated with a step-wise change in aFe³⁺. It is shown that the CFA technique yields a Nernstian response of a 30 mV per decade change in aFe³⁺ in saline citrate buffers in the range of 10⁻²² to 10⁻¹ M Fe³⁺. Validation of the CFA technique in organic-free, UV-oxidized seawater has demonstrated that the response of the Fe^III ISE is internally consistent with the well-known inorganic speciation equilibria occurring in natural seawater. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 284–288, 1999