Mobile phase and temperature studies in the reversed-phase liquid chromatography of inosine and guanosine compounds

Analysis of purines and pyrimidines by mixed partition-adsorption normal-phase high-performance liquid chromatography

This paper summarizes the results in the development of mixed partition-adsorption (MPA) normal-phase high-performance liquid chromatography published in the last 10 years. The MPA normal-phase systems are an alternative approach not only to the adsorption normal-phase mode but also to the most widely used reversed-phase mode in the separation area of purine and pyrimidine derivatives. It is shown that the MPA systems are applicable in analytical practice.

Application of mixed partition-adsorption systems in high-performance liquid chromatography of purines and pyrimidines

Separation of the test mixtures of some purine and pyrimidine derivatives on silicas (types A and B) in adsorption normal-phase (A-NP) and mixed partition-adsorption normal-phase (MPA-NP) mode has been studied. When the A-NP mode is used the peak shapes are unsatisfactory (especially on type A silica). At the same time MPA-NP systems show a good peak symmetry on all silica types. The findings have demonstrated that the MPA-NP mode offers a specific selectivity. This allows MPA-NP systems to supersede reversed-phase systems in some application areas.

Normal-phase high-performance liquid chromatographic separations using ethoxynonafluorobutane as hexane alternative. I. Analytical and chiral applications

A novel, environmentally friendly, fluorinated solvent--ethoxynonafluorobutane--has been used to replace n-hexane in normal-phase HPLC applications. Fast gradients of methanol in ethoxynonafluorobutane on a cyano column have been successfully applied to the separation of steroids, benzodiazepines, NSAIDs, tricyclic antidepressants, beta-adrenergic blocking agents and mixtures of purines and pyrimidines. Small amounts of triethylamine and trifluoroacetic acid added to such gradients significantly improved peak shape and column performance for basic and acidic solutes. Ethoxynonafluorobutane and its mixtures with methanol have also been demonstrated to have a unique selectivity in chiral HPLC applications.

Separation of purines and pyrimidines by normal-phase high-performance liquid chromatography using dimethyl sulfoxide in binary and ternary eluents

Chromatographic systems with a silica sorbent and mobile phases containing dimethyl sulfoxide have been studied. It has been established that the substitution of isopropanol by dimethyl sulfoxide in binary eluents results in a specific selectivity of the chromatographic system and shows an improvement of the peak shape for the solutes under study. When mobile phases consisting of hexane, isopropanol and dimethyl sulfoxide (solvents with a limited mutual solubility) are used, changes in retention characteristics and peak symmetry are caused by a transition from adsorption to partition sorption mechanism. The stationary liquid phase is generated dynamically in the pores of silica, even in the mobile phases not saturated with a polar component. If the phase ratio of the column reaches 0.1, partition dominates over adsorption and such mixed partition-adsorption (MPA) systems show very good peak symmetry for the solutes under study. The investigation has shown that dimethyl sulfoxide-containing MPA systems are applicable in analytical practice.

Chromatographic properties of cytosine, cytidine and their synthetic analogues

A direct reversed-phase high-performance liquid chromatographic (RP-HPLC) assay was used for the study of the effects of methanol concentration, pH, flow-rate of the mobile phase and column temperature on the retention of the natural nuclei acid components cytosine and cytidine and their synthetic 1-beta-D-arabinofuranosyl, 5-aza and 6-aza analogues. The pKa values were also determined. The greatest changes were observed with changes in pH. The relationship between the capacity factors and the hydrophobicity of the compounds studied was also investigated.

Correlation of structure and retention behaviour in reversed-phase high-performance liquid chromatography. II. Methionine-enkephalin-related glycoconjugates

Reversed-phase high-performance liquid chromatographic elution data for methionine-enkephalin-related glycoconjugates were analysed as a function of the identity and position of the sugar-peptide linkage. It was shown that binding to the column could be correlated with the degree of sugar moiety protection. Replacement of either the phenylalanine or methionine residue in the peptide backbone of the glycoconjugates with its D-enantiomer leads to a considerably stronger retention on a reversed-phase column. The dependence of retention times on the methanol concentration in the mobile phase suggested that, under the conditions studied, there are different retention mechanisms for glycopeptides containing unprotected sugar moieties in the molecule.

Determination of purine nucleosides and their bases by high-performance liquid chromatography using co-immobilized enzyme reactors

A selective and sensitive assay of inosine, guanosine, hypoxanthine, guanine and xanthine by high-performance liquid chromatography with immobilized enzyme reactors was developed. The separation was achieved on a Capcell Pak C18 column (15 cm x 0.46 cm I.D.) with a mobile phase of 0.1 M phosphate buffer (pH 8.0) containing 7 mM sodium 1-hexanesulphonate and 0.1 mM p-hydroxyphenylacetic acid. The fluorimetric detection of hydrogen peroxide using immobilized peroxidase and p-hydroxyphenylacetic acid was applied to the assay of these compounds, which were oxidized to yield hydrogen peroxide in the presence of immobilized enzyme (purine nucleoside phosphorylase, guanase and xanthine oxidase). Enzyme reactions occurred sufficiently without post-column addition of reagents. Enzymes that catalysed the conversion of purine compounds were co-immobilized on aminopropyl controlled-pore glass packed in stainless-steel tubing. The detection limits were 30-200 pg per injection.

DNA-nitrosourea interactions. High-performance liquid chromatography of cross-linked dinucleosides and substituted deoxynucleosides

A reconstituted mixture of five cross-linked dinucleosides possibly involved in DNA-nitrosourea interactions, and of their degradation products (nucleobases, deoxynucleosides and mono- or disubstituted deoxynucleosides), was analysed by reversed-phase high-performance liquid chromatography using C18 columns and an diode-array detector. The chromatographic conditions for separating the twenty-one investigated compounds were optimized, and the compounds were identified by both their retention times and their UV spectra. A structure-retention time relationship was observed under suitable conditions and is discussed. Its validity was confirmed by the prediction of the retention time of a new cross-linked dinucleoside synthesized for this purpose.

Reversed-phase high-performance liquid chromatography of nucleoside analogues. Simultaneous analysis of anomeric D-xylo- and D-lyxofuranonucleosides and some other D-pentofuranonucleosides

Reversed-phase high-performance liquid chromatography using a C18 column was applied to the analysis of reconstituted mixtures of previously synthesized alpha, beta D-xylo- and D-lyxofuranonucleosides as well as a number of commercially available D-ribo- and D-arabinofuranonucleosides. From a detailed study of various parameters (size of support particles, nature and pH of the mobile phase, temperature), optimized conditions were established. Correlations between the retention times and structures of the bases, the orientations of the secondary hydroxyl groups of the sugar moiety and the anomeric configurations of the nucleosides are also reported.