The design of Flow Injection manifolds to give the best detection limits for methods involving on-line chemical derivatisation Part 2. The spectrophotometric determination of chloride
The optimisation of a flow injection manifold for the spectrophotometric determination of chloride is described. Factors contributing to the baseline noise due to refractive index and reagent absorption effects are removed by a combination of design features. Firstly, a double-line manifold is used; secondly, pulse-dampers and a packed bed reactor are incorporated into the flow lines and thirdly a delay coil is introduced to resolve the valve switching peaks from the determinand peaks. The appropriate conditions for obtaining the maximum sensitivity are found from an off-line experiment and the guidelines established on the basis of the well-stirred tank model for dispersion applied to the design of the operating parameters of flow rate ratio and volume injected. Good agreement between the predicted and experimentally determined values were obtained. The resulting manifold gave a linear calibration from the detection limit (4.5-8.0 ppb) to 2.00 ppm
