Diol columns

HPLC-k correlation ODS column Diol column quoted lit. average, Helweg et al. 1997) 3.33 (range 3.24-3.40) (slow stirring method-HPLC/fluo., De Maagd et al. 1998)... 

HPLC-k correlation ODS column Diol column, Helweg et al. 1997)... 

Fig. 16.6. (a) HPLC chromatograms for reaction mixture A. HPLC conditions C18 (20 x 100 mm Nova-Pak TM), gradient 5-95% acetonitrile/water, with 0.1% TFA (b) SFC chromatogram for reaction mixture A. SFC conditions Diol column (21.2 x 150 mm, Berger Instruments), gradient 5-60% Methanol with 0.5% dimethylethylamine in carbon dioxide [11],... 

Lou, D.-W., Saito, Y., Zarzycki, P. K., Ogawa, M., and Jrrmo, K. (2006b). Isocratic separation of ginsenosides by high-performance liquid chromatography on a diol column at subambient temperatures. Ancd. Bioanal. Chem. 385, 96-104. 

Amine modifiers in the mobile phase have been used in conjunction with silica-gel columns to provide more-stable columns. In addition, the use of diol-type silica-gel columns for the separation of food sugars has been reported. These columns provide separations similar to those afforded by aminopropyl silica gel, but they are much more stable. The use of these diol columns, whenever practical, is therefore recommended. 

Despite the low reproducibility and short life time of the NP columns, they are widely used owing to their better selectivity and resolution power, which enable the separation of (3- and y-isomers easily. The most used stationary phases are silica, aminopropyl- or diol-bonded [476], A more accurate description of the column used can be found in a review about tocol-derivatives analysis by Abidi [477], Kamal-Eldin et al. [478] compare the performance of new silica-type columns, six different silica columns, three amino columns, and one diol column. The new generation column results are much more repeatable and therefore suitable for vitamers analysis. 

These adsorbants are typically used for polar compounds that are not well retained by reverse-phase adsorbants. The colunms are conditioned by washing with 5-10 bed-volumes of the solvent which will be used to elute the analyte. The sample is loaded onto the column in a solvent, which is not sufficiently strong to elute it. Washing of the column is often carried out with a moderate polarity organic solvent, e.g. alcohol-free methylene chloride. Polar compounds are then eluted with methanol or mixtures of methanol and acidic buffer (for basic compounds) or methanol and alkaline buffer (for acidic compounds). Diol columns have been used to good effect in the extraction of polar drugs from pharmaceutical creams. ... 

Liquid chromatography cleanup on a LiChrosorb Diol column has been further proposed for the offline purification of chloramphenicol residues from bovine muscle and eggs (32). An online approach based on reversed-phase principles has also been described for isolation of chloramphenicol residues from swine kidney by an automated column switching system (63). Use of a protein exclusion column (Hisep) has been also suggested in an online trace-enrichment method for the determination of chloramphenicol in animal tissues (52). By employing a column-switching system, all chloramphenicol that eluted from the protein exclusion column was trapped at the entry of a 5 m Supelcosil LC-18 preconcentration column, to be subsequently back-flashed into the analytical column. 

In this case, a binary gradient is used, which is meant mainly to yield a better resolution of glycolipid classes. When the lipid extracts do not contain glycolipids, this phase of the separation can be omitted, and hence an isocratic mobile phase can be used. Also, for extracts poor in molecular species, the silica gel column may be omitted, for the diol column on its own provides resolution of the major phospholipid classes. 

JKG Kramer, L Blais, RC Fouchard, RA Melnyk, KMR Kallury. A rapid method for the determination of vitamin E forms in tissues and diet by high-performance liquid chromatography using a normal-phase diol column. Lipids 32 323-330, 1997. 

Berge and Deye studied the effect of column surface area on the retention of polar solutes [18]. They found that there was a linear relationship between retention and the surface area. 4-Hydroxy benzoic acid was used as a model acidic compound, and sulfamethazine, sulfanilamide, sulfi-somidine, and sulfapyridine were used as the model basic compounds. The separations were carried out on a packed Nucleosil Diol column with a methanol-modified carbon dioxide as the mobile phase. The UV detector was used for the analysis. It was observed that 0.1% acetic acid for the acidic solutes and 0.1% isopropylamine for basic solutes was required in the methanol to achieve the separations. The efficiency was found to be similar for 100-, 300-, and 500-A packing materials. 

Diastereomeric complexes can also be formed by ion-pairing of an enantiomer with a chiral counterion. In order to form this diastereomeric complex, it has been postulated that at least three interaction points between the ion pair are required [250]. Nearly all of these form weak complexes in aqueous mobile phases. Consequently, the chromatographic methods that have been developed have been either silica or diol columns with low-polarity mobile phases. Enantiomeric amines, such as the beta-blockers, have been optically resolved when (-l-)-lO-camphorsulfonic acid was used as the chiral counterion [251]. Enantiomers of norephedrine, ephedrine, pseudoephedrine, and phenyramidol have all been resolved from their respective enantiomers with n-dibutyltartrate [252]. Enantiomers of naproxen, a chiral carboxylic acid, are resolved from each other by either using quinidine or quinine in the mobile phase [253]. In these studies, silica... 

Antibiotics represent a chemically quite heterogenous category of compounds, for which the Cl 8 phases appear sorbents of the first choice. A group of these compounds (tetracyclines) was successfully separated by open tubular capillary electrochromatography using Cl8 modified capillaries. The results reported to be obtained in this system were better than those obtained with either monolithic columns or open diol columns [123] (Fig. 10.26). 

G. Sworn, W. M. Marrs, and R. J. Hart, Characterisation of carrageenans by high-performance size-exclusion chromatography using a LiChrospher 1000 DIOL column, J. Chromatogr., 403 (1987) 307-311. 

NP-HPLC Normal-phase liquid chromatographic methods applying Diol-columns or common silica columns are well suited for the analysis of the total steryl ferulate content. They require very little sample preparation, as total lipid extracts can frequently be directly injected into the column without purification or fractionation. Run times for SFs are also relatively short, and a good separation from other lipid components can be obtained in less than 10 min in traditional HPLC systems. Depending on the column type and the sample, SFs elute as one or two peaks. Two peaks are obtained from the separation of SFs, which have ferulic acid both in cis- and trans- configuration (Nystrom et ah, 2008). The relative retention time (obtained with a silica column and hexane/ethyl acetate 97 3 as eluent) of the cis- form is about 0.5 smaller than that of steryl irans -ferulates (Akihisa et al., 2000). 

Figure 11.2 Normal-phase separation of Ts and T3 with a Diol column and three different mobile phases. A. hexane/MTBE, 96 4, B. hexane/isopropanol, 99 1, C. hexane/1-4 dioxane, 96 4. (Kamel-Eldin et al., 2000).

The anhydride was formed as a side product in this reaction impacting yield. However, in an RP mobile phase, both the mesylate and anhydride would revert back to the carboxylic acid. Derivatization would produce the same product for both the mesylate and the anhydride. The reaction components were separated and quantihed under NP conditions using a diol column with a 0.1v/v% TFA in heptane/THF mobile phase (Figure 14-2). This method was used monitor the reaction such that the level of the carboxylic acid intermediate was less than 0.5% in the reaction mixture. 

Fig. 11.4. Plm of log/t predicied by Eq. (II.14 against cxporiincnial data determined on a diol column for 36 ehalcone derivatives with heptane eluent containing O.Sfif tetrahydrofuran. dioxane. ethanol, propanol, trctanol or dimeihylformamide. (Reprinted with permission from K. A//aoui and L. Morin-Allory. Chromatographia. 42 (1996). 389. Copyright Friedr. Vieweg and. Sohn.)...

I. Ehman-Borjesson and M. Harrod, Analysis of nonpolar hpids by HPLC on a diol column, J. High Resolut. Chromatogr. 20 516 (1997). 

Fig. 1 Separation of benzylamines (a) On a Deltabond Octyl column (100 X 2 mm, 5 tm) using pure carbon dioxide (0.5 mL/min) at 40°C and 180 bar (b) on a Diol column (100 X 2 mm, 7 tm) using 5% methanol in carbon dioxide (0.5 mL/min) at 40°C and 182 bar (c) on a Diol column (250 X 4.6 mm, 5 tm) using 10% methanol (containing 0.6% isopropylamine) in carbon dioxide (2 mL/min) at 40°C and 200 bar. Reprinted from /. Chromatogr. A Vol. 785, T. A. Berger, Separation of polar solutes by packed column supercritical fluid chromatography, p. 9. Copyright 1997, with permission from Elsevier Science.)...

Basic solutes such as amines, ethers, esters, and ketones are preferentially retained on amino and diol columns when compared to cyano columns [14,15]. The amino phase is a good alternative to the cyano column for a change in selectivity. When analyzing ketones and aldehydes, the aminopropyl phase should be carefully used due to the possible reactivity of the amino group with these substances. This may lead to the formation of imines and the bonded phase maybe easily oxidized [13],... 

Figure 3. LC/MS selected ion current profiles of a low standard containing 0.5 ng/ml 13-cis, 0.5 ng/ml all trans and 20 ng/ml tetradeuterated 13-cis retinoic acid. Stationary phase Diol column (1 x 250 mm) mobile phase 15% toluene...

Kramer, J.K.G., Blais, L., Fouchard, R.C., Melnyk, R.A., and Kallury, K.M.R. 1997. A Rapid Method for the Determination of Vitamin E Forms in Tissues and Diet by High-Performance Liquid Chromatography Using a Normal-Phase Diol Column. Lipids. 32 323-330. 

To change selectivity based on the strong solvent, isopropanol may be replaced with methylene chloride, methyl t-butyl ether, or ethyl acetate (separate k optimization is required). However, note should be made of the relatively high UV cutoffs of these solvents when UV detection is to be used. As an alternative to cyano columns, diol columns may be investigated as before. Other stationary phases are also available, but generally provide poorer stability. Triethylamine or acetic acid may be added to the mobile phases to curtail tailing problems. 

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