Characterization and Evaluation of C₁₈ HPLC Stationary Phases Based on Ethyl-Bridged Hybrid Organic/Inorganic Particles

Abstract

The characterization and evaluation of three novel 5-microm HPLC column packings, prepared using ethyl-bridged hybrid organic/inorganic materials, is described. These highly spherical hybrid particles, which vary in specific surface area (140, 187, and 270 m(2)/g) and average pore diameter (185, 148, and 108 A), were characterized by elemental analysis, SEM, and nitrogen sorption analysis and were chemically modified in a two-step process using octadecyltrichlorosilane and trimethylchlorosilane. The resultant bonded materials had an octadecyl surface concentration of 3.17-3.35 micromol/m(2), which is comparable to the coverage obtained for an identically bonded silica particle (3.44 micromol/m(2)) that had a surface area of 344 m(2)/g. These hybrid materials were shown to have sufficient mechanical strength under conditions normally employed for traditional reversed-phase HPLC applications, using a high-pressure column flow test. The chromatographic properties of the C(18) bonded hybrid phases were compared to a C(18) bonded silica using a variety of neutral and basic analytes under the same mobile-phase conditions. The hybrid phases exhibited similar selectivity to the silica-based column, yet had improved peak tailing factors for the basic analytes. Column retentivity increased with increasing particle surface area. Elevated pH aging studies of these hybrid materials showed dramatic improvement in chemical stability for both bonded and unbonded hybrid materials compared to the C(18) bonded silica phase, as determined by monitoring the loss in column efficiency through 140-h exposure to a pH 10 triethylamine mobile phase at 50 degrees C.

State-of-the-art in immobilized polymer stationary phases for high-performance liquid chromatography

“…More recently, hybrid support particles, containing methyl 26,27 or ethylene 28 groups embedded into the silica structure, prepared using the sol-gel process from a mixture of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) or bis(triethoxysilyl)ethane (ETEOS). The presence of these groups in the silica structure confers greater chemical stability, nominally to pH 12, as compared to the bare silica support.…”

O desafio de analisar solutos básicos por cromatografia líquida em modo reverso: algumas alternativas para melhorar as separações

“…Nas fases estacionárias preparadas pela imobilização do poli( metiloctilsiloxano) 54,55,58,59 e poli(metiltetradecilsiloxano) 56,57 sobre a superfície da sílica ou nas fases estacionárias ZirChrom, [40][41][42][43][44][45][46][47][48][49][50][51][52][53] que apresentam uma grande quantidade de zirconóis residuais, a retenção de solutos básicos é dominada por interações sinérgicas entre os sítios capazes de fazerem interações iônicas e a porção hidrofóbica da fase estacionária. 32,34 Estas fases estacionárias retêm fortemente solutos básicos, em uma faixa de pH entre 6 e 8, na qual os silanóis residuais (ou zirconóis no caso do zircônia) estão desprotonados e os solutos protonados.…”

Highly stable high performance liquid chromatography stationary phase based on direct chemical modification of organic bridges in hybrid silica

“…Polymer-coated [16], horizontally polymerized [17,18], bidentate [5,13] and polar embedded stationary phases are typical examples. In recent years, a unique class of organic/inorganic hybrid silica materials have been developed, which is normally prepared by condensing alkoxysiloxanes with monosubstituted XSi(OR) 3 or organic-bridged (R O) 3 SiRSi(OR ) 3 [19][20][21][22]. Compared with inorganic silica materials, the columns packed with hybrid materials have increased chemical stability toward a broader pH range [15,19,22].…”

“…In recent years, a unique class of organic/inorganic hybrid silica materials have been developed, which is normally prepared by condensing alkoxysiloxanes with monosubstituted XSi(OR) 3 or organic-bridged (R O) 3 SiRSi(OR ) 3 [19][20][21][22]. Compared with inorganic silica materials, the columns packed with hybrid materials have increased chemical stability toward a broader pH range [15,19,22]. The most widely applied hybrid silica substrates are monomethyl-substituted [22] (condensation of MeSi(OEt) 3 and TEOS) and ethylene-bridged [15,19] (condensation of (EtO) 3 SiCH 2 CH 2 Si(OEt) 3 and TEOS) series developed in recent decades.…”

“…Compared with inorganic silica materials, the columns packed with hybrid materials have increased chemical stability toward a broader pH range [15,19,22]. The most widely applied hybrid silica substrates are monomethyl-substituted [22] (condensation of MeSi(OEt) 3 and TEOS) and ethylene-bridged [15,19] (condensation of (EtO) 3 SiCH 2 CH 2 Si(OEt) 3 and TEOS) series developed in recent decades. It was claimed that they could be used under mobile phase with pH value up to 10-11.…”