Generation of time-dependent concentration profiles using a reduced-size continuous-flow manifold

A computer-controlled manifold allowing the automatic generation of concentration profiles is described. For this purpose, the sample or standard solution is placed inside a semi-closed loop to which diluent is incorporated at a given flow rate, while the solution is removed at the same flow rate and directed towards the detector. The flow manifold, which works in a similar way to the tank model, includes a membrane micropump to recirculate the solution in the semi-closed loop. For simplicity purposes in the assessment of the system, a flame atomic absorption spectrometer is used for both withdrawing liquid and detection, although the basic idea can easily be extended to other detectors. The experimental data, verified by measuring the calcium, magnesium, sodium and potassium contents of some soft drinks demonstrate that the approach is reliable and may be a basis for developing portable instruments of reduced-size.