Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System

Abstract

This paper investigates the ability of seven chromatographic response functions to measure the quality of chromatograms obtained in hydrophilic interaction liquid chromatography (HILIC). First, the functions were tested on a set of simulated chromatograms and differences in their mathematical design were discussed. Second, the functions were evaluated on the experimentally obtained chromatograms in HILIC analysis of model mixture consisted of beta agonists and antagonists. The ranking of chromatograms obtained by different functions was significantly different, implying that the accuracy of the optimization procedure is strongly dependent on the function that was selected as an output. Investigation of potential drawbacks of each function was conducted and general recommendations concerning the use of chromatographic response functions in optimization strategies are proposed.

Keywords:

• Beta agonists and antagonists
• Chromatographic response function (CRF)
• HILIC

Acknowledgments

The authors thank the Ministry of Education and Science of the Republic of Serbia for supporting these investigations with Project 172052.

Notes

x₁ – acetonitrile content in the mobile phase (vol %); x₂ – pH of the mobile phase; x₃ – concentration of ammonium acetate in the water phase (mM).

^a Coded factor levels.

^b Real factor levels.

θ_s.l: resolution criterion of adjacent peaks calculated by Eq. 7; t₁ – retention time of the first eluting peak; t_f – retention time of the last eluting peak; Rs_s.l – resolution factor between adjacent peaks; B_CRF – Berridge's chromatographic response function, COF – Glajch et al.'s chromatographic optimization function; CRS – Schlabach chromatographic resolution statistics, Do_CRF – Dose's CRF; CEF – Morris’ chromatographic exponential function, D_CRF – Duarte's chromatographic response function and N_CRF – new chromatographic response function developed by the authors of this paper.

*The meaning of symbols are in given in the legend of Table 2.