Only slices are measured of very long segments of solute molecules that are injected into columns in chromatographic systems. Since the concentration of solute molecules changes during elution as a function of time, the observed signal should be reconstructed for a comparison of experimental results with theory. The influence of response time on the observed signal in high-performance liquid chromatography experiments was investigated in detail using a C-18 column for the measurement of caffeine in pure methanol as eluent. The response function influenced the observed signal by converting the square signal of pulse flow into a chromatographic peak. At faster linear flow rates (LFRs), the response function influenced the observed shape of the chromatographic peak, whereas diffusion dominated at slow LFRs. By convolution of the square signal with the response function, it was possible to predict the shape of the observed signal and chromatographic parameters and to provide an alternative explanation to the van Deemter equation. By using the shape of a known response function and modelling the new theory to data, it was proposed that the injected solute molecules were eluted over long distances through the chromatographic column, distances that are much longer than the physical length of the system.

Plate theory and adsorption theory are the main tools available for understanding chromatographic experiments. Both theories predict a Gaussian distribution of solute molecules within the tubular system. However, Gaussian concentration distributions are observed predominantly at slow linear flow rates, while asymmetric concentration distributions are observed at the linear flow rates most used in chromatography. Allegedly, this asymmetry originates from an inhomogeneous distribution of grain sizes in the column and column overload. However, it is an experimental fact that the distribution of chemicals within an injected volume of solute changes as a function of time, while the response is measured simultaneously. Accordingly, the obtained signal cannot be compared to the theory before some type of time‐based deconvolution of the data has been performed. Adjustments to high‐performance liquid chromatography data were thus proposed through empirical equations that describe the relevant time values, peak height, peak area, and parameters of the van Deemter equation. It was proposed that the transfer of solute from the front to the rear part of the pulse during laminar open‐ended flow occurs at rate that depends on the linear flow rate, and to a lesser extent, on properties of the response function.

This article presents a novel sample preparation strategy that employed a custom-synthesized glucose - fructose (G-F) specific molecularly imprinted polymer (MIP) powder as an adsorbent for the simultaneous and selective extraction, isolation and pre-concentration of total glucose and fructose from the complex and `dirty` sample matrix of ‘100%’ fruit juices purchased from retail shops in Palapye, Botswana. The prepared G-F MIP powder demonstrated high selectivity, effective extraction and isolation for glucose and fructose from real samples of `100%` fruit juice samples as evidenced by the calculated high extraction efficiencies (EEs) of over 90%, with low percentage relative standard deviations (%RSD) of below 7% for n=6, for both glucose and fructose when compared to the low EEs of below 25% by the non-imprinted polymer (NIP), regarded as the control. Furthermore, the G-F MIP showed lower selectivity towards the analogous molecules; maltose and lactose as supported by the low EEs of below 31%. With the high affinity for glucose and fructose, the selective sample preparation strategy proposed herein presented itself as a potential procedure to be employed to improve the accurate analysis of adulterated artificial sugar sweeteners that are usually illegally added to the so-called `100%` fruit juices by producers to improve their taste.