Performance of polymer-coated silica C18 packing materials prepared from high-purity silica gel

Ohtsu, Yutaka; Shiojima, Yoshihiro; Okumura, Tatsuya; Koyama, Junichi; Nakamura, Kiyoshi; Nakata, Okitsugu; Kimata, Kazuhiro; Tanaka, Nobuo

doi:10.1016/s0021-9673(01)96760-3

Cited by 90 publications

(22 citation statements)

References 27 publications

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“…[1][2][3][4][5][6][7][8][9][10] The following studies on the endcapping method of ODS-silica gels without organic solvent as a silylation medium were reported: endcapping in a vapor phase and its evaluation by supercritical fluid chromatography (SFC); 1 optimization and characteristics of a high-temperature silylation method;…”

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confidence: 99%

Endcapping of Octadecylsilyl-Silica Gels Using Supercritical Fluid as Reaction Medium

et al. 1999

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A method for endcapping of octadecylsilyl (ODS)-silica gels was developed using supercritical carbon dioxide as a silylation medium. The effects of temperature and pressure of carbon dioxide on the deactivation of the gels were investigated under the silylation conditions at 100 -220˚C and 11.8 -24.5 MPa. High-performance liquid chromatographic evaluation using caffeine and phenol as test compounds indicated that the most inert gels were obtained from the endcapping under 180˚C and 24.5 MPa. Endcapped ODS-silica gels, which were commercially available, could be further deactivated under these conditions. The inertness of the gels was also evaluated by supercritical fluid chromatography (SFC) using pyridine and phenol as test compounds. The effectiveness of the proposed method was clearly observed in the SFC evaluation.

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Endcapping of Octadecylsilyl-Silica Gels Using Supercritical Fluid as Reaction Medium

et al. 1999

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“…To explore this possibility, we attempted to examine the influence of residual silanols by comparing log k values for the same compounds measured on the C18-UG column with the previous data obtained on the SG-column. Both columns were designed by the same manufacturer, 25,26) to eliminate residual silanols but the main difference in the characteristics is the amount of silanols; the more recently developed UGtype is considered to be essentially free from accessible residual silanols. Among different ways proposed to assess amount of silanols, 26,[34][35][36] we evaluated qualities of these columns in terms of a separation factor, a C/P (k caffeine / k phenol ) 26,34) ; a C/P ϭ0.359 and 0.313 for SG and UG, respectively, describing well their characteristic (Smaller value is thought to indicate smaller amount of residual silanols).…”

Section: Resultsmentioning

confidence: 99%

“…The packing materials of these columns are high-purity silicone-polymer coated silica gels chemically modified with octadecyl groups and were developed so as to suppress extremely small traces of residual silanols. 25,26) Retention factors were measured at 25°C according to the previous procedure. 11,12) A Shimadzu LC9A liquid chromatograph, equipped with an SIL-6A auto injector, an SPD-6AV UV detector (Shimadzu), an ERC-7510 refractive index (Erma, OpticalWorks), and a C-R4A Chromatopac (Shimadzu), was used.…”

Section: )mentioning

confidence: 99%

Hydrophobicity Parameters Determined by Reversed-Phase Liquid Chromatography. XV: Optimal Conditions for Prediction of log Poct by Using RP-HPLC Procedures.

Yamagami

Kawase

Iwaki

2002

CHEMICAL & PHARMACEUTICAL BULLETIN

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Recently, in connection with the remarkable development of computational technologies for rational drug designs, the necessity has become apparent of rapid measurement or estimation of molecular properties of chemicals having a potential for medical use. In particular, hydrophobicity (as expressed by the logarithm of 1-octanol/water partition coefficient, log P oct ) is identified as one of the most important properties that govern potencies; its prediction has attracted much attention from medicinal chemists, agrochemists and many investigators in various fields such as pharmacology, toxicology, environmental chemistry and food chemistry. 1,2)Instead of measuring log P oct by the standard but time-consuming shake-flask method, reversed-phase chromatography (RP-HPLC) has increasingly been used as a powerful tool to predict log P oct from the readily accessible retention factor, log k, (given by kϭ(t R Ϫt 0 )/t 0 where t 0 and t R express elution times of the non-retained substance and sample, respectively).Extensive studies have been made to establish an optimal RP-HPLC system providing a good linearity between log P oct and log k.3-10) Many workers have used an ODS-type column with methanol-water mobile phases to obtain a normalized parameter, log k W (k W : the retention factor extrapolated to 0% organic modifier), as an alternative to log P oct . 3,5,8) In our experience, this log k W approach works well for non-polar solutes but tends to provide overestimated log P oct values for strong H-acceptors. [10][11][12][13][14][15] From systematic studies of log k obtained under various HPLC conditions for typical heteroaromatic compounds such as (di)azines, furans and thiophenes, we were led to the conclusion that the use of an eluent containing around 50% methanol, which usually provides a more direct correlation with log P oct , is the most convenient and practical procedure for rapid estimation of log P oct provided H-donors (amphiprotic compounds) are treated separately.11-15) Our results so far obtained are illustrated graphically in Fig. 1. This conclusion has been derived from the following results.First, we have shown that, for each series of monosubstituted (di)azines, log P oct can be excellently correlated with log k in different compositions of methanol-water eluents by a general formula Eq. 1 containing two terms correcting for H-bonding effects: 16) log kϭalog P oct ϩrs I ϩsS HA ϩconst.( 1) where the s I parameter represents the Charton's inductive electronic substituent constant, 17) and S HA designates the substituent H-acceptor scale that we have recently defined where the value of S HA is set at unity for H (the unsubstituted * To whom correspondence should be addressed. The use of log k derived from reversed phase (RP)-HPLC retention times provides a convenient method for estimating log P oct values (P oct : 1-octanol/water partition coefficient). In order to establish optimal HPLC conditions, the difference between chromatographic (C18 modified column and aqueous methanol eluents) and bulk solve...

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“…Othsu et al [16] deposited silicone monomer on the substrate, subsequently followed by in situ polymerization and attachment of, e.g., octadecyl ligands. There is evidence that a number of these phases exhibit superior stability and shielding properties to conventional ligand-bonded phases.…”

Section: Introductionmentioning

confidence: 99%

Characterization and stability of silanized and polymercoated octadecyl reversed phases

Hetem¹,

Haan²,

Claessens³

et al. 1991

Journal of Chromatography A

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Performance of polymer-coated silica C18 packing materials prepared from high-purity silica gel

Cited by 90 publications

References 27 publications

Endcapping of Octadecylsilyl-Silica Gels Using Supercritical Fluid as Reaction Medium

Endcapping of Octadecylsilyl-Silica Gels Using Supercritical Fluid as Reaction Medium

Hydrophobicity Parameters Determined by Reversed-Phase Liquid Chromatography. XV: Optimal Conditions for Prediction of log Poct by Using RP-HPLC Procedures.

Characterization and stability of silanized and polymercoated octadecyl reversed phases

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