MONITORING TIME-VARYING CONCENTRATIONS IN SAMPLE STREAMS BY MULTIPLE-INPUT CHROMATOGRAPHY

The possibility of monitoring time-varying concentrations with convent ional chromatography or correlation chromatography (CC) is restricted. The highest frequency that can be monitored is, due to Shannon, limit ed for conventional chromatography to (2xchromatogram length)(-1), and for CC, due to a moving average effect, to (sequence length)(-1). A m ethod is presented in which considerable higher frequencies can be mon itored. Theoretically the power spectral density of the chromatographi cal peak shape limits the upper frequency that can be monitored. The m ethod originates from CC. A pseudo-random binary sequence (PRBS) is us ed as injection pattern. The detector signal however is not correlated or deconvoluted with a PRBS as in CC. The time-varying concentrations of the components are described as functions of time and a number of parameters, e.g. parameters of a Fourier series. These parameters then are optimised in a non-linear fitting procedure. A detector signal is calculated using the parameters, the known PRBS and known peak shapes ; and the squared differences with the real detector signal are minimi sed. The results from simulated experiments and practical experiments are shown.