Use of chromatographic system peaks for continuous quantitative analysis

A study was made to establish whether the size of system peaks, which occur in chromatography with multi-component mobile phases, is a linear function of the concentration of the components. In the two chromatographic systems studied, it was found that the size of the system peaks is proportional to concentration. Using the fact that the injection of concentrations lower than that in the mobile phase results in negative system peaks whereas the injection of higher concentrations yields positive peaks, a simple method to determine the concentration of the components in the mobile phase is described. The approach seems to be robust although the retention times of some mobile phase components might be affected by the concentration of other components. The results presented indicate that system peaks can be used to monitor continuously various streams such as rivers, waste waters and physiological fluids.