Reversed-phase columns properties

Prediction of Starting Conditions from Analyte Structures and Reversed-phase Column Properties... 

Some of the characteristic column volumes outlined in the previous argument were determined by Alhedal et al (11) in the examination of a commercially available reverse phase column packing, Zorbax Cs. These authors examined the exclusion properties of the interstitial volume of the column by measuring the retention volume of a number of salts of different molecular volume.The substances used, in ascending order of ion volume, were as follows,... 

Separation of diastereoisomeric peptides by HPLC is more common. Since each diastereo-isomer has different physicochemical and biological properties, this is of great interest. Separations of diastereoiosomeric di- and tripeptides have usually been performed on reversed-phase columns. Cahill et al. (119) separated diastereoisomeric amino acids and derivatized dipeptides using esters of the /V-hydroxysuccinamide of f-butyl carbonyl-L-amino acid on Cl8 and C8 columns. Linder et al. (120) separated amino acid and peptide derivatives on an RP-C8 column, adding a metal chelate. Mixtures of DL and LD-dipeptides can be separated by RP-HPLC into two peaks, one containing LL- and DD-isomers, the other containing LD and DL-isomers. Sep-... 

One of the major applications of SEC is polymer characterization. As many of the properties that characterize a polymer, including hardness, brittleness, and tensile strength, are related to the molecular weight distribution, GPC can be used to identify subtle differences between polymer materials. The GPC technique can also be used as an alternative to reversed-phase LC for samples, such as creams, ointments, and lotions. These samples contain high levels of hydrophobic materials, such as triglycerides, which could bind strongly to the reversed-phase column and cause column fouling. 

A wide variety of reverse-phase columns obtained from different manufacturers can be used. We found that the best results were obtained with columns that have already been used for some time (6 mo) for lipid analyses. These columns revealed separation properties different to those of new columns. 

In addition to GC properties, Kurz [4] has investigated HPLC retention of 106 PCDE congeners. Retention indexes (RI) were measured on three reversed phase columns having phenyl, cyanopropyl, and octadecyl phases. Like HRGC retention, HPLC retention of PCDEs depends on the structure. LC data of PCDEs have been used to determine water solubility and octanol-water partition coefficients [66]. 

Smitz et al. [ 114] subjected to multivariate analysis the retention data of 9 selected test analytes determined on 26 reversed-phase columns. By PCA the columns were grouped in three classes of similar properties. The authors were able to detect the deviation of some columns from the typical trend observed for RP-8, RP-18 or polymer-coated materials. The deviation could be explained in terms of the extreme physicochemical properties of the column. 

Mixtures for specific property tests of reversed-phase columns a = separation factor, k = retention factor and As = asymmetry factor... 

The HPLC method uses the procedure described in the section on the separation of collagenase digest—a reversed-phase column (normal pore Cig) eluted by a water-acetonitrile gradient with formic acid as the additive. Alternatively, formic acid can be substituted with trifluoroacetic acid (due to its ion-killing properties at lower concentrations, e.g., 3 mM). Separation and resolution is slightly better with trifluoroacetic acid as the ionpairing agent. 

An HPLC method is attractive for flavor fractionation since it uses a different set of physical properties for separation than GC does. A flavor isolate may be separated by adsorption or reverse/normal phase chromatography. Adsorption chromatography is a good initial choice since it has the greatest column capacity and can handle the widest range of types of compounds [53]. Fractions based on adsorption affinity could then be further fractionated on a normal or reverse phase column [54]. 

The hydrophobic properties of a series of 5-aIl l-, 5-alkenyl- and 5-alI yl-substituted deoxyuridines were defined from their retention behaivour on silica and reversed-phase columns. Zeatin and its riboside were determined in plant tissues by solid-phase extraction and cation-exchange h.p.l.c. Sugar and nucleoside H-phosphonates have been separated by anion-exchange h.p.l.c., and by flow injection analysis in which the components are hydrolysed, oxidised and the orthophosphate so generated is detected colorimetrically. ... 

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