Preparation and properties of reversed phases

Karch, Karl; Sebestian, I.; Halász, I.

doi:10.1016/s0021-9673(00)82233-5

Cited by 249 publications

(57 citation statements)

References 30 publications

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“…This is in agreement with the work of KARCH et al 7) and independently with the work of HEMETSBERGER et al 8) Both groups were able to prepare excellent packings from SI 100 silica and methyloctadecyldichlorosilane. Fig.…”

Section: In-situ Columnssupporting

confidence: 91%

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

White¹,

FOX²

1982

J. Antibiot.

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"Hydrophobic chromatography", which is a variation of reverse phase chromatography, is applicable to the analysis of cephalosporin C derivatives, especially in fermentation broths. Unfortunately, there are no commercial C18 columns which are entirely suitable for this class of compounds.For this reason C18 columns were prepared by an in-situ bonding technique and were optimally designed for cephalosporin C derivatives.Mono-, di-and trifunctional octadecyl bonding agents were used with 10 Ftm silica of both 60 A and 100 A pore diameter. The best results were obtained with the difunctional agent, methyloctadecyldichlorosilane, and 100 A silica. "Endcapping" of residual silanol groups with a trimethylsilylation agent was optional, since good results were obtained with both a plain C18 column and one that was "endcapped" ."Hydrophobic chromatography" is a variation of the reverse phase technique in which a neat (i .e., no organic component) aqueous solvent is used as the mobile phase. This mode of chromatography is very useful for the analysis of polar ionic compounds. In particular, it is well suited for the separation and quantitation of cephalosporin C derivatives, especially in fermentation broths.In a previous papery we described hydrophobic conditions for the separation of cephalosporin C using a large particle (37-50 icm), medium efficiency C18 column. In a second paper2) we presented an improved method for the analysis of cephalosporin C derivatives using a small particle (10,um), high efficiency column prepared in-house by chemically bonding octadecyltrichlorosilane to silica by an insitu technique. An in-situ column was used because no commercially available column was completely satisfactory for use in the hydrophobic mode. Poor efficiencies and broad asymmetrical peaks are often obtained with commercial columns. In addition, both retention and resolution properties are inadequate, especially with early eluting compounds such as deacetylcephalosporin C and deacetoxycephalosporin C.Cephalosporin C derivatives have been separated by us3) and others4) with reverse phase ion-pair chromatography.The principal advantage of this approach is that early eluting compounds such as deacetylcephalosporin C and deacetoxycephalosporin C are retained on the column long enough to be well separated from interfering substances in fermentation broths. However, with a properly prepared in-situ column as described in this paper, good separations can be obtained without the need for ion-pairing.The work2) that we reported previously on the hydrophobic chromatography of cephalosporin C derivatives employed an in-situ C18 column. However, at that time there was no attempt made to discover the optimum conditions for producing these in-situ columns. This paper gives the results of a study that was carried out on the preparation of C18 columns especially suited for the hydrophobic

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Section: In-situ Columnssupporting

confidence: 91%

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

White¹,

FOX²

1982

J. Antibiot.

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“…Based on the earlier mentioned seven parameters, PCA was applied again and seven groups of columns were observed: non-endcapped C 18 columns with poor surface coverage based on acidic silica (type A), polar embedded C 8 and C 18 columns, other C 8 and C 18 columns with different degrees of endcapping and different silicas, some specific C 8 columns, C 18 columns based on acidic, type A silica and/or with poor surface coverage, modern C 18 columns based on less acidic, type B silica and relatively hydrophobic C 18 columns. Based on the PCA plots, N PB was found to be highly correlated with k PB and therefore removed.…”

Section: Further Methods Development By Euerby Et Almentioning

confidence: 99%

“…Since there are more than 600 different RP-LC stationary phases available on the market, the chromatographic performance may differ considerably. Various descriptions have been employed in the attempt to differentiate C 18 stationary phases with different properties. Unfortunately, these descriptions are not very helpful nor have they been applied consistently.…”

Section: Introductionmentioning

confidence: 99%

“…It can be determined using different methods: retention of nitrobenzene compared to naphthalene or benzene (in normal phase mode) [18][19][20], peak symmetry or retention times of basic compounds [16,[21][22][23][24][25], separation of ortho-, meta-and para-toluidine [24,26,27] or selectivity factors for aniline/phenol or caffeine/phenol [28][29][30][31]. However, as it was found by Claessens et al, different silanol activity tests are not interchangeable because the term 'silanol activity' is not well defined and its value is dependent on the measurement conditions [32].…”

Section: Introductionmentioning

confidence: 99%

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Three methods to characterize reversed phase liquid chromatographic columns applied to pharmaceutical separations

Németh

Haghedooren

Noszál

et al. 2008

Journal of Chemometrics

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Selecting a suitable reversed phase liquid chromatographic (RP-LC) column for a particular separation is complicated. More than 600 brands of C 18 columns are available on the market. Therefore, determining the characteristics influencing the selectivity of the different stationary phases is necessary. In this paper, three different methods to characterize RP-LC columns are compared. Hoogmartens et al. developed a column characterization system based on test methods from literature, which were reduced with principal component analysis (PCA), and led to four final chromatographic parameters. The second method studied is this of Euerby et al. who developed a column classification system using six parameters, based on the method of Tanaka and also applying PCA. The third method, developed by Snyder et al. is different from the other two. It uses five parameters, calculated by multiple linear regression from the retention data of 18 solutes. The suitability of the column classification systems was examined on pharmaceutical separations. It seems that all three methods can facilitate the selection of a suitable column for an analysis.

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“…Recent advances in instrument technology permitting the use of ternary phases (Darney et al, 1983) (Table 2) including C,*, C8, C2 and phenyl functionalities. Chromatographic selectivity on these phases has been variously reported to remain constant (Unger et al, 1976), to increase with carbon chain length (Karch et al, 1976) and to plateau following an initial increase (Majors and Hopper, 1974). In practice, the most important influence of chain length is the effect on partition ratio which decreases as the length of the carbon chain is reduced (Lotfy, 1981).…”

Section: Stationary Phasementioning

confidence: 99%

Chromatography as a reference technique for the determination of clinically important steroids

Robards

Towers

1990

Biomedical Chromatography

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Chromatographic methods (paper chromatography, thin layer chromatography, high performance liquid chromatography, gas chromatography and gas chromatography-mass spectrometry) for the determination of clinically important steroids in biological specimens are reviewed. The emphasis is on the use of gas chromatography, gas chromatography-mass spectrometry and high performance liquid chromatography as reference rather than routine techniques. Chromatographic methods are compared with colorimetric, fluorimetric and radioimmunoassay procedures in terms of simplicity of operation, cost and ability to analyse large numbers of specimens. The importance of correct specimen collection and storage are discussed. Sample preparation techniques for the various analytical methods are described. These include extraction of free and conjugated steroids from serum, plasma, urine and saliva by solvent partition, with polymer-based resins such as Amberlite XAD-2, DEAE-Sephadex and Sephadex resins bonded with various other function groups and, more recently, with chemically bonded reversed-phase silicas.

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Preparation and properties of reversed phases

Cited by 249 publications

References 30 publications

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

Custom made C18 columns for the hydrophobic chromatography of cephalosporin C derivatives.

Three methods to characterize reversed phase liquid chromatographic columns applied to pharmaceutical separations

Chromatography as a reference technique for the determination of clinically important steroids

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