Simultaneous determination of ionic species by sequential injection analysis using a sandwich technique with large sample volumes

In this work we investigated the feasibility of using large sample volumes in sequential injection analysis with a view of determining various analytical parameters in a unique sample injection. The use of two reagents separated by a large sample volume allows the determination of two different parameters in the sample. The accuracy with which the two resulting peaks (one for each reaction) can be resolved and the linear working ranges are dependent on both the injected sample volumes and reagent, together with their concentrations. Under given conditions, the proposed methodology can be applied over a certain analyte concentration range. For validation purposes the proposed methodology was applied to the simultaneous determination of Fe(II) and nitrite ions for their well-known o-phenanthroline and Griess reactions, respectively.