Selectivity enhancement for the separation of tocopherols and steroids by integration of highly ordered weak interaction sites along the polymer main chain

Abstract

A novel alternating copolymer-based organic phase was synthesized using a new N-substituted maleimide monomer for the development of alternating copolymer-grafted silica for high-performance liquid chromatographic applications. This new monomer (DGMI) was copolymerized with octadecyl acrylate (ODA) from 3-mercaptopropyltrimethoxysilane-grafted silica to produce Sil-poly(ODA-alt-DGMI). The organic phase was characterized by the elemental analysis and the diffuse reflectance infrared Fourier transform spectroscopy. Tocopherol isomers and steroids were used as analytes for the evaluation of the chromatographic selectivity profiles of this novel stationary phase. The selectivity of this column was then compared with a polymeric ODS column and previously developed another alternating copolymer-grafted silica (without the glutamide-derived moiety) column, Sil-poly(ODA-alt-N-octadecylmaleimide). The complete baseline separation of tocopherol isomers in an isocratic mode has been achieved within 25 min with the Sil-poly(ODA-alt-DGMI). The separation of eight kinds of estrogenic steroids and corticoids has also been achieved in an isocratic mode with this column. Significant differences in separation selectivity between Sil-poly(ODA-alt-DGMI) and polymeric ODS columns were observed towards the steroids, and compared with the reference columns, a better separation profile for these analytes was obtained with the Sil-poly(ODA-alt-DGMI). The results of this investigation indicated that the enhancement of selectivity of Sil-poly(ODA-alt-DGMI) towards the test analytes arose from the multiple interaction mechanism such as hydrophobic effect, carbonyl-π and hydrogen-bonding interactions, and such integrated interactions originated from the addition of two amide groups in the N-substituted maleimide monomer.

A Sulfonic‐Azobenzene‐Grafted Silica Amphiphilic Material: A Versatile Stationary Phase for Mixed‐Mode Chromatography

“…Under the same chromatographic conditions, a mixture of four steroids including estriol, 17α‐estradiol, 17β‐estradiol, and estrone were successfully separated in Sil‐PAzO within six minutes as shown in Figure 4. The positions of the isomer pair 17α‐estradiol and 17β‐estradiol were baseline‐separated within 5 min on Sil‐PAzO, which can be a challenge for the ODS column 12. As shown in Figure 4, the same mixture cannot be separated on the ODS column under the same chromatographic conditions and the retention order of the last three analytes was reversed.…”

“…The positions of the isomer pair 17a-estradiol and 17b-estradiol were baseline-separated within 5 min on Sil-PAzO, which can be a challenge for the ODS column. [12] As shown in Figure 4, the same mixture cannot be separated on the ODS column under the same chromatographic conditions and the retention order of the last three analytes was reversed.…”

Enhancement of Thermal Stability and Selectivity by Introducing Aminotriazine Comonomer to Poly(Octadecyl Acrylate)-Grafted Silica as Chromatography Matrix

“…The typical procedure is as follows. Sil-MPS was prepared by using porous silica particles diameter 5 µm, pore size 12 nm, and surface area 300 m 2 g −1 , (YMC CO., LTD., Kyoto, Japan) and MPS according to a previously reported method [23]. Sil-MPS was mixed with given amounts of ODA, AT, and AIBN as a radical initiator in DMSO, and then, the mixture was gently stirred at 70 • C for 6 h. The reaction mixture was filtered and sufficiently washed with DMSO, chloroform, and methanol.…”

L‐Lysine‐derived highly selective stationary phases for hydrophilic interaction chromatography: Effect of chain length on selectivity, efficiency, resolution, and asymmetry

“…One of the most important chromatographic techniques is reversed‐phase (RP) separation, where hydrophobic stationary phases are usually used with polar mobile phases for the separation of nonpolar analytes. RP‐HPLC being increasingly used because of the versatility and continuous development of new stationary phases and instrumentation . Commonly, two types of n‐alkyl chromatographic stationary phases are used in RP separation depending on synthesis procedure (monomeric and polymeric C 18 ) .…”

“…One of the most important chromatographic techniques is reversed-phase (RP) separation, where hydrophobic stationary phases are usually used with Article Related Abbreviations: APS, Aminopropyltrimethoxysilane; DRIFT, Diffuse reflectance Fourier transform; NPLC, Normal-phase liquid chromatography; SIL, Grafted silica; TEA, Triethylamine; TGA, Thermogravimetric analysis; Urea-12, Nα,Nε-bis(dodecylaminocarbonyl)-L-lysine; Urea-6, Nα,Nε-bis(hexylaminocarbonyl)-L-lysine polar mobile phases for the separation of nonpolar analytes. RP-HPLC being increasingly used because of the versatility and continuous development of new stationary phases and instrumentation [1][2][3][4][5]. Commonly, two types of n-alkyl chromatographic stationary phases are used in RP separation depending on synthesis procedure (monomeric and polymeric C 18 ) [6][7][8][9][10].…”