Studies on the stability of n-alkyl-bonded silica gels under basic pH conditions

Effective separation of peptides using highly dense thermo-responsive polymer brush-grafted porous polystyrene beads

“…6 shows that the retention factors of bradykinin increased with increasing pH, because the hydrophobicity of bradykinin increased with increasing pH close to its pI 12.5 (Table 3) [34]. In general, it is difficult to retain basic analytes by reversed-phase chromatography with isocratic elution, because silica beads as a base material are instable at high pH condition [20]. Moreover, upon the use of conventional polymer beads as a base material, the gradient elution of organic solvent must be able to work for retaining basic peptides [35,36].…”

“…Silica beads are instable under high pH condition, and the instability always limits the application and requires neutral pH mobile phases [20]. Even though silica-based stationary phases are used in neutral condition, the reproducibility of separation decreases with repeated use due to the hydrolysis of silica surface.…”

Review on the chemical and thermal stability of stationary phases for reversed-phase liquid chromatography

“…The reported pH limits in neutral and alkaline eluents at which silica and its chemically bonded derivatives can be used safely vary in between pH 7 and 10 ( [87][88][89][90][91] and references therein). If one considers that the rate of silica dissolution strongly depends on a large number of different parameters, these large differences in pH recommendations are not surprising.…”

“…Furthermore, also the determination and understanding of the physico-chemical and hence chromatographic properties of RP columns is still limited and subject of ongoing investigations ( [2,4,[20][21][22][23][24][25][26] and references therein). Finally, the chemical and thermal stability of RP columns and thus their longevity under practical eluent and other experimental conditions is also an important issue [2,[27][28][29][30].…”

Preparation of thermo-responsive polymer brushes on hydrophilic polymeric beads by surface-initiated atom transfer radical polymerization for a highly resolutive separation of peptides

“…Silica-based stationary phases are widely used in HPLC systems because of their good performance as chromatographic stationary phase. However, silica beads become instable under aqueous alkaline conditions (pH higher than 8.0) due to the hydrolysis of silica [21]. Therefore, thermo-responsive chromatography using polystyrene beads as starting materials have developed for improving stability under all-aqueous mobile phase [18,19].…”