Hollow-fibre membrane for sample introduction in a flow-injection system : Determination of carbon disulphide in air

A hollow-membrane fibre is used for the introduction of gaseous compounds into a flow-injection system. The sampling system consists of a certain length of asymmetric hollow-fibre membrane in which an acceptor stream is stopped for a fixed period of time. The analyte permeates from the surrounding environment through the membrane and is accumulated in the acceptor solution, then pumping is resumed. The method is tested for the determination of carbon disulphide in ambient air. The detection range of the method is from 3 to at least 30 mg l−1

Impulse/response functions of individual components of flow-injection manifolds

The dispersion behaviour of the various individual parts making up a flow-injection manifold is often difficult to establish because it is virtually impossible to obtainthe required very small injection and detection volumes. It is shown that it is possible, under suitable experimental conditions, to find the impulse/response functionof each component by means of a deconvolution process of the response functions have been established, the response function of any arrangement can be predicted by convoluting the impulse/response functions of all the individuaol parts involved. Convolution and deconvolution were done in the Fourier domain, by using a fast FT algorithm

Use of the hunt filter to optimize the determination of impulse-response functions of individual component parts of flow-injection manifolds

The dispersion behaviour of the various individual parts making up a flow-injection manifold can be expressed by means of impulse-response functions. These functions can be determined by deconvolution of the response curves obtained with and without the part concerned. Special attention is paid to a procedure to decrease the influence of noise. It is shown that good results can be obtained with a Hunt filter which operates in the Fourier domain

Impulse-response functions of several detectors used in flow-injection analysis

A procedure for the determination of the impulse-response function of a detector is given. Its application to photometers, ion-sensitive field effect transistors, a potentiometric detector at constant current and a voltammetric detector shows that the impulse-response function can be used to obtain specific information about the performance of the detector in the manifold. This function clearly shows the contribution of the detector to the peak broadening and how the detector generates the final signal from the presented concentration profile. From this information one could derive improvements to the detector, such as changing the construction of the detector cell, minimizing the influence of other parts of the manifold or adapting the attached electronics