Dj. Louwerse et al., MONITORING TIME-VARYING CONCENTRATIONS IN SAMPLE STREAMS BY MULTIPLE-INPUT CHROMATOGRAPHY, Analytica chimica acta, 346(3), 1997, pp. 285-297
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.