Investigation of the retention behaviour of steroids with calixarene‐based stationary phases by modern NMR spectroscopy

Abstract

Investigation of the retention behaviour of steroids with calixarene-based stationary phases by modern NMR spectroscopy A separation of four structurally similar steroids was performed on two calix[8]arene based stationary phases. It was observed that two of the steroids had a reversed retention order when the columns were changed. This implies that two different retention mechanisms are taking place when the analytes are separated. In order to evaluate the mechanism responsible for the reversal of the retention order an extensive study of the interactions between the stationary phases and the analytes was undertaken. By performing a series of transferred NOESY measurements in the suspended state valuable information was obtained about the strengths of the interactions between the analytes and the stationary phases. The magnitudes of the integrals from the trNOESY measurements showed a good correlation with the k9 values obtained from the chromatographic evaluation. The retention mechanism is based mainly on hydrophobic interactions. However, the reversal of the elution order was mainly due to an additional p-p interaction between one of the analytes and the stationary phase.

Recent Advances in the Analysis of Steroid Hormones and Related Drugs

“…As an example, the transferred NOESY study of the interactions between various steroids and calix [8]arene-based stationary phases is mentioned. 51 Similar studies related to chiral interactions are shown in the last section of this review.…”

Characterization of calixarene- and resorcinarene-bonded stationary phases

“…We assume that specific interactions with the cavities of the calixarenes and resorcinarenes are responsible for these phenomenon. HR-MAS-NMR studies confirm a stronger interaction of chlormadinone acetate with AIII in comparison to BIII, which was due to better -interactions [38]. Thus, phases with supramolecular selectors are able to detect differences of the analytes with similar lipophilicity.…”

Chromatographic analysis of some drugs employed in erectile dysfunction therapy: Qualitative and quantitative studies using calixarene stationary phase

“…Several techniques such as UV , NMR , electrochemical , chromatographic , and capillary electrophoretic techniques were used to ensure that calixarenes make inclusion complexes with different analytes. Calixarenes have several applications in anion receptors , CE as additives , polymeric materials , GC , and HPLC .…”