Cross injection analysis: Concept and operation for simultaneous injection of sample and reagents in flow analysis

This work presents a new flow injection strategy, called ‘cross injection analysis’ or CIA, an alternative cost-effective approach in flow analysis. The flow platform is made from a rectangular acrylic block, approximately 5×3×1.5 cm (x×y×z), with crossing cylindrical channels drilled out along the x- and y-axis of the block. The outlet from the single x-axis channel is connected to a detector flow cell. This channel is filled with the carrier solution. The flow in the x-axis channel is driven by a computer controlled single-channel peristaltic pump. The multiple y-axis channels, running perpendicular to the x-channel, are connected to a multi-channel peristaltic pump. These channels contain the sample and reagent solutions that flow across the intersection zones of the channels. To mix the sample and reagent with subsequent detection of the reaction zone, flow is applied along the x-axis channel, while flow in the y-axis channels is stopped. We successfully demonstrated the validity of the CIA technique by the spectrometric determination of Fe(II) using 1,10-phenanthroline and the speciation of Fe(II) and Fe(III). To place the CIA technique within the context of flow analysis, a brief overview of the evolution of flow injection analysis and its later innovative development is included.