Immobilized polymeric stationary phases using metalized silica supports

Core-shell silica@pyridyl conjugated microporous polymer as a stationary phase for high performance liquid chromatography

BACKGROUND

Because of the advantages of good selectivity, high sensitivity, and fast analysis, high performance liquid chromatography (HPLC) has become one of the modern analytical techniques in wide application range, such as biological analysis, environmental detection, pharmaceutical and food inspection, agriculture and other fields. The stationary phase greatly decides the chromatographic separation performance, so the development of novel stationary phase is most important for HPLC.

RESULTS

Pyridyl conjugated microporous polymers (P-CMP) with one to four layers were modified on the surface of amino silica to obtain a novel core-shell material (SiO2@P-CMP) by the layer-by-layer assembly strategy and Chichibabin reaction. The relationship between the structure of SiO2@P-CMP and chromatographic performance was carefully investigated, and the retention mechanism was revealed. The interactions including π-π stacking, hydrophobic effect and hydrogen bond gradually enhanced with the increase of P-CMP layers on the silica surface. Compared with C18 column, SiO2@P-CMP columns displayed better separation selectivity for polycyclic aromatic hydrocarbons (PAHs). According to the relative retention values (α), the separation performance of SiO2@P-CMP columns (α = 1.144-1.884) for PAH isomers and other analytes was obviously better than that of C18 column (α = 0.998-1.487). Furthermore, the SiO2@P-CMP column with four layers was selected to separate different types of analytes (eight PAHs, four bisphenols, four estrogens and nine phthalates), and the peak order of analytes was different from that on the C18 column due to the influence of hydrogen-bonding and π-π interactions. The relative standard deviations (n = 10) of retention time and peak area on SiO2@P-CMP column were between 0.28 % and 1.98 %.

SIGNIFICANCE AND NOVELTY

Pyridyl conjugated microporous polymer was introduced as the stationary phase for the first time in HPLC. The proposed column displayed better separation characteristics compared to Zorbax SB-C18 column. It provided a new idea for the separation of small molecules and the development of chromatographic packing or extraction material.

Multifunctional silane polymers for persistent surface derivatization and their antimicrobial properties

We demonstrate a versatile methodology combining both covalent surface anchoring and polymer cross-linking that is capable of forming long-lasting coatings on reactive and nonreactive surfaces. Polymers containing reactive methoxysilane groups form strong Si-O-Si links to oxide surfaces, thereby anchoring the polymer chains at multiple points. The interchain cross-linking of the methoxysilane groups provides additional durability to the coating and makes the coatings highly resistant to solvents. By tailoring the chemical structure of the polymer, we were able to control the surface energy (wetting) of a variety of surfaces over a wide range of water contact angles of 30-140 degrees . In addition, we synthesized covalently linked layer-by-layer polymeric assemblies from these novel methoxysilane polymers. Finally, antibacterial agents, such as silver bromide nanoparticles and triiodide ions, were introduced into these functional polymers to generate long-lasting and renewable antiseptic coatings on glass, metals, and textiles.

Stability studies of stationary phases from poly(methyltetradecylsiloxane) sorbed and immobilized onto metalized and unmodified silicas

Stationary phases for RP-HPLC were prepared from metalized (titanized and zirconized) and unmodified silica particles using sorbed and immobilized poly(methyltetradecylsiloxane) (PMTDS). Different immobilization procedures, such as gamma irradiation and thermal treatments, were used for the preparation of the immobilized PMTDS phases. The stabilities of these stationary phases were evaluated by passing alkaline (pH 10) mobile phase through 60 mm x 3.9 mm columns of the different phases, with periodic tests to evaluate chromatographic performance. The results show that higher stabilities were obtained with stationary phases based on PMTDS immobilized on zirconized silica, these phases being 50% more stable than their titanized silica counterparts and 400% more stable than those based on unmodified silica. These supports provide higher chemical stability to the laboratory-made stationary phases, when compared with chemically bonded silica-based phases.

Preparation and characterization of poly(methyltetradecylsiloxane) stationary phases immobilized by gamma radiation onto zirconized silica

The preparation of stationary phases with enhanced chemical stability in alkaline eluents has been the principal objective of many chromatographers. New and improved silica substrates and advanced chemical modification methods are among the possibilities being investigated to reach this objective. The present work has evaluated these two possibilities for new stationary phases. First, the silica surface was modified by reaction with zirconium tetrabutoxide to produce zirconized silica particles having about 21% (w/w) of zirconium. Then poly(methyltetradecylsiloxane) (PMTDS) was immobilized onto this surface using different doses (50-120 kGy) of gamma radiation. These new phases were characterized using elemental analysis and infrared and solid-state (29)Si-nuclear magnetic resonance (NMR) spectroscopies. These new stationary phases presented column efficiencies of about 68,000 plates m(-1), symmetric peaks for apolar compounds and retention factors that depend on the irradiation dose and show improved stability in high pH mobile phases. The separation of several pharmaceuticals at pH 11 is presented.

Poly(methyltetradecylsiloxane) immobilized onto silica for extraction of multiclass pesticides from surface waters

A new material based on poly(methyltetradecylsiloxane) (PMTDS) thermally immobilized onto a silica support has been tested as a sorbent for the solid-phase extraction (SPE) from water of several pesticides used in soybean cultivation. The SPE methodology was developed and validated for six of these pesticides (imazethapyr, imazaquin, metsulfuron-methyl, bentazone, chlorimuron-ethyl and tebuconazole) according to the International Conference on Harmonization directives and the results were compared with those obtained with a commercial C18 SPE cartridge. The PMTDS-based sorbent gives results similar to the commercial sorbent with recoveries and precisions in agreement with directives for residue analysis. The quantification limits, after concentration, of all the pesticides evaluated were 1.0 microg L(-1), below the levels imposed by the principal regulatory agencies. The PMTDS-based sorbent preparation is fast, easy and reproducible and the cartridges are less expensive than similar commercial SPE materials.