Performance of global retention models in the optimisation of the liquid chromatographic separation (II): Complex multi-analyte samples

• Published in: Analytica chimica acta Vol. 1320; p. 343019
• Main Authors: Peiró-Vila, P., Torres-Lapasió, J.R., García-Alvarez-Coque, M.C.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-09-2024
• Subjects: Chromatography, High Pressure Liquid - methods; Chromatography, Liquid - methods; Global retention models; Medicinal plants; Multi-linear gradient elution; Optimisation of resolution; Plant Extracts - analysis; Plant Extracts - chemistry; Plant Extracts - isolation & purification; Plants, Medicinal - chemistry; Medicinal plants; Multi-linear gradient elution; Global retention models; Optimisation of resolution
• ISSN: 0003-2670; 1873-4324; 1873-4324
• DOI: 10.1016/j.aca.2024.343019

Enhancing the quality control of medicinal plants is a complex challenge due to their rich variety of chemical compounds present at varying and extreme concentrations. Chromatographic fingerprints, which have become essential for characterising these complex natural materials, require achieving optimal separation conditions to effectively maximise the number of detected peaks. The challenges in optimising fingerprints and other complex multi-analyte samples include the unavailability of standards, the presence of unknown constituents and the substantial workload that would require conventional optimisation methods based on models.
This work introduces an interpretive optimisation approach which operates on the premise of predicting chromatograms using global models. Initially, a multi-linear gradient experimental design is sequentially executed to accommodate all peaks in the chromatogram in an adequate time window. Following this, a small set of sample peaks (reference peaks) is selected based on their consistent traceability across all chromatograms in the design. Using this reference dataset, a global model is constructed, initially focused solely on the reference peaks and later extended to encompass all detected peaks in the sample. The aim is to find gradients that maximise resolution while minimising analysis time. These optimised gradients are applied successfully to enhance the separation of medicinal plant extracts, with particular emphasis on peppermint and pennyroyal extracts.
The proposed optimisation relying on global models can be applied to highly complex samples even in the absence of standards, or in cases where standards are available but their use is impractical due to workload constraints. Moreover, in discerning the most promising gradients for highly complex samples, peak purity has demonstrated superior reliability and competitiveness compared to peak capacity as chromatographic objective function.
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•Optimisation of complex samples based on global retention models.•Sequentially built one-node gradient design was applied.•Successful predictions for full chromatograms including around 150 peaks.•Pareto plots and genetic algorithms applied to find the most suitable gradient.•Peak capacity yields misleading optima in relation to peak purity.