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In this work, a general view of multi-commutation in flow analysis process is presented. The manuscript comprises a comprehensive description of the basic manifolds designed to demonstrate the multi-commutation concept including the operational modes and the inherent features. A multi-function flow system with the ability to carry out three-operation modes without any hardware modification is also described. Intending to demonstrate the versatility of the flow system based on multi-commutation process, a set of experiments was designed comprising an in-line dilution and stopped flow approach. Standard solutions of iron and of orthophosphate were selected as models to demonstrate the analytical potential of the proposed system. The results obtained are presented and discussed.

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A novel flow-based strategy for implementing simultaneous determinations of different chemical species reacting with the same reagent(s) at different rates is proposed and applied to the spectrophotometric catalytic determination of iron and vanadium in Fe-V alloys. The method relies on the influence of Fe(II) and V(IV) on the rate of the iodide oxidation by Cr(VI) under acidic conditions; the Jones reducing agent is then needed. Three different plugs of the sample are sequentially inserted into an acidic KI reagent carrier stream, and a confluent Cr(VI) solution is added downstream. Overlap between the inserted plugs leads to a complex sample zone with several regions of maximal and minimal absorbance values. Measurements performed on these regions reveal the different degrees of reaction development and tend to be more precise. Data are treated by multivariate calibration involving the PLS algorithm. The proposed system is very simple and rugged. Two latent variables carried out ca 95% of the analytical information and the results are in agreement with ICP-OES.