Abstract
Aim. To study the effect of 5,11,17,23-tetrakis(diisopropoxyphosphonyl)-25,26,27,28-tetrapropoxycalix[4]arene and oсtаkis(diethoxyphosphoryloxy)-tert-butylcalix[8]аrene additives to the MeCN – H2O mobile phase (86:14) on the selectivity of the separation of aromatic compounds by the reversed-phase high performance liquid chromatography (RP HPLC) using a Separon SGX C18 support.Results and discussion. The process of complexation of phosphorylated calix[4,8]arenes with benzene derivatives in the mobile phase plays a key role in the RP HPLC separation of analytes. The stability constants of the inclusion complexes and the chromatographic separation coefficients of the analytes depend on the nature of the aromatic compounds and the cavity size of the calixarene macrocycle.Experimental part. The HPLC analysis was performed in acetonitrile – water (86:14) solution using a Separon SGX C18 column. The stability constants of the calixarene complexes were determined using the dependence of 1/k’ chromatographic parameters of benzene derivatives on the calixarene concentration in the mobile phase. Molecular modelling of the calixarene complexes was carried out using a Hyper Chem 8.0 program.Conclusions. The phosphorus-contained calixarenes due to their ability to form supramolecular complexes with aromatic molecules can be used as additives to the RP HPLC mobile phase and improve separation of benzene derivatives.Received: 14.05.2020Revised: 24.06.2020Accepted: 27.08.2020
Highlights
The process of complexation of phosphorylated calix[4,8]arenes with benzene derivatives in the mobile phase plays a key role in the reversed-phase high performance liquid chromatography (RP HPLC) separation of analytes
Molecular modelling of the calixarene complexes was carried out using a Hyper Chem 8.0 program
The phosphorus-contained calixarenes due to their ability to form supramolecular complexes with aromatic molecules can be used as additives to the RP HPLC mobile phase and improve separation of benzene derivatives
Summary
Complexation of calix[4]arene 1 and calix[8]arene 2 with benzene derivatives was studied by the RP HPLC method described in papers [18, 19]. The calixarene additives to the mobile phase decrease the capacity coefficient k’ of benzene derivatives due to the formation of the host–guest inclusion complexes. It has been shown that the addition of calixarenes to the mobile phase improves the separation selectivity of benzene analytes (Таbles 1, 2). Calix[8]arene 2 additive to the mobile phase improves the separation selectivity of benzene derivatives (α1/α0 = 1.06 – 1.74). 8. The energy minimized molecular structures of calixarene 1 (a) and its complexes with р-аmіnоphеnоl stabilized by the hydrogen bonds Ar–О–Н...O=P at the upper rim (b) and Ar–О–Н...О(Рr) at the lower rim (c) of the macrocycle. The RMS (standard deviation of the word root mean square) gradient was equal to 0.01 kcal/A·mol
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