Characterisation of Gas-Chromatographic Poly(Siloxane) Stationary Phases by Theoretical Molecular Descriptors and Prediction of McReynolds Constants.

Angelo A D’Archivio,Andrea Giannitto

doi:10.3390/ijms20092120

Angelo A D’Archivio, Andrea Giannitto

Open Access

https://doi.org/10.3390/ijms20092120

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Abstract

Retention in gas–liquid chromatography is mainly governed by the extent of intermolecular interactions between the solute and the stationary phase. While molecular descriptors of computational origin are commonly used to encode the effect of the solute structure in quantitative structure–retention relationship (QSRR) approaches, characterisation of stationary phases is historically based on empirical scales, the McReynolds system of phase constants being one of the most popular. In this work, poly(siloxane) stationary phases, which occupy a dominant position in modern gas–liquid chromatography, were characterised by theoretical molecular descriptors. With this aim, the first five McReynolds constants of 29 columns were modelled by multilinear regression (MLR) coupled with genetic algorithm (GA) variable selection applied to the molecular descriptors provided by software Dragon. The generalisation ability of the established GA-MLR models, evaluated by both external prediction and repeated calibration/evaluation splitting, was better than that reported in analogous studies regarding nonpolymeric (molecular) stationary phases. Principal component analysis on the significant molecular descriptors allowed to classify the poly(siloxanes) according to their chemical composition and partitioning properties. Development of QSRR-based models combining molecular descriptors of both solutes and stationary phases, which will be applied to transfer retention data among different columns, is in progress.

Highlights

Quantitative structure–retention relationship (QSRR) method is a specialised branch of quantitative structure–activity(property) relationship (QSA(P)R) approach aimed at relating the retention of the analytes in separation chromatographic systems to their molecular structure [1,2,3]
The dataset investigated in this work consists of 29 poly(siloxane) stationary phases belonging to poly(methylphenylsiloxane), poly(methyltrifluoropropylsiloxane) and aspoly(cyanoalkylmethylphenylsiloxane) in the case of the molecular stationary phases previously investigated
QSRRwith models were subgroups displayed in Tables 1 and The together the first generated by MLRconstants coupled X, with genetic (GA)

Summary

Introduction

Quantitative structure–retention relationship (QSRR) method is a specialised branch of quantitative structure–activity(property) relationship (QSA(P)R) approach aimed at relating the retention of the analytes in separation chromatographic systems to their molecular structure [1,2,3]. Retention in gas chromatography (GC) is mainly governed by the extent of the intermolecular interactions between the solutes and the stationary phase, since the gaseous mobile phase is not involved in the partition mechanism under the typical experimental conditions of analytical separations [9] In this regard, the ability of the stationary phase of being involved in inductive, dispersive, orientation, lone-pair electron and H-bonding interactions determines the column polarity, while selectivity is related with its capacity to participate in specific intermolecular interactions. In linear free energy relationships (LFERs) and LFER-based QSRRs [9,10], empirical or semiempirical molecular descriptors have been conceived to quantify the abilities of the solutes to take part in the postulated intermolecular interactions with the chromatographic phases. In spite of their conceptual and historical importance, the LFER molecular descriptors are not readily available for most solutes of current analytical interest

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Conclusion