Utilization of MS Excel for processing of unresolved peaks on the chromatograms

Abstract

Conventional software for the processing of chromatograms does not provide the possibility of peak
simulation with a Gaussian function. This causes a problem for the correct calculation of the areas of unresolved peaks. The purpose of this paper was to propose a method for computer-generated simulation of the peaks with Gaussian functions in MS Excel. The parameters of the chromatogram (time and values of the detector responses) are imported into MS Excel. The peaks are simulated using Gaussian functions with manually selected parameters, including retention times (close to the experimental value), standard deviations, and peak heights to fit the section of the chromatogram with unresolved peaks. The processing ensures more exact calculation of the quantitative ratio of the substances, both for the peaks of similar width and for the peaks with markedly different effectiveness in the numbers of theoretical plates. Meanwhile, software with manual peak resolution by vertical divider (a built-in function of the software) is also suitable in the former case, although in the latter case it may provide incorrect results. The simulation was performed for the chromatograms of flax seed oil triacylglycerides and the anthocyanins of the fruit of the grape cultivar Moldova. The latter contains 3-glucosides and 3,5-diglucosides of common anthocyanins at the same time, which are markedly different in peak width at half height on the chromatogram. It was shown that some closely eluted pairs of compounds (such as positional triacylglycerols, for instance) can still be described by a Gaussian distribution, but the deviations increase in case of unequal quantities of the isomers. In this case, the resulting peak shape can be simulated using the main Gaussian with addition of another small one with a slightly greater retention. This type of simulation was found suitable not only for peaks with possible existence of positional isomers but also for a single-compound peak (e.g. tri-α-linolenoate).