High-performance liquid chromatography of biologically important pyrimidine derivatives with ultraviolet—voltammetric—polarographic detection

Reversed-phase high-performance liquid chromatography of pyrimidine bases and nucleosides. Application of solvophobic theory

The chromatographic behaviour of some natural and modified pyrimidine bases and nucleosides on an octadecyl stationary phase was studied. The retention and selectivity parameters of the separation of the compounds studied were derived on the basis of solvophobic theory. The mechanism of base and nucleoside interactions with the surface of the hydrocarbonaceous stationary phase is discussed. The best separation is observed at pH 3.5 for the bases and at pH 4.8-5.2 for the nucleosides. An increase in the solute surface tension results in an increased selectivity of separation. When the surface tension and the ionic strength of the mobile phase are not kept constant, there are considerable deviations in retention from that predicted by solvophobic theory.

Determination of melamine in air by high-performance liquid chromatography with ultraviolet detection

An air sampling and liquid chromatographic separation method for melamine is described. Collection efficiency on 13-mm glass fibre filters was determined. No breakthrough was detected under a contamination level of 0.4 mg/m3 for 40-1 air samples. The detection limit for a 60-1 air sample at 215 nm is 450 ng/mg. Retention behaviour of melamine on four different reversed-phase columns is described. Column packings tested are Spherisorb ODS, Supelcosil ODS, Spherisorb CN and PRP-1. Results of electrochemical detection studies are discussed.

Optimization of a high-performance liquid chromatographic method for the determination of nucleosides and their catabolites. Application to cat and rabbit heart perfusates

A high-performance liquid chromatographic method is described for the separation of nucleosides and related compounds in a single isocratic run. The separation of a standard mixture of at least thirteen compounds is achieved within 15 min on a new type of reversed-phase column 25 cm long, filled with 5-micron particles of Select B. Pre-treatment of the silica particles before silanization has given this type of reversed-phase material unique characteristics for basic and acidic compounds. Chromatograms are shown to compare the effectiveness of the Select B column for the separation of nucleosides with that of other C18 and C8 phases. The separation is achieved with 0.3 M ammonium dihydrogen phosphate (pH 4.00) and a mixture of methanol, acetonitrile and tetrahydrofuran. Detection is carried out with a variable-wavelength UV detector at 254 nm. Sample preparation and the influence of the organic solvents, pH and buffer concentration are described. To illustrate the applicability of the method, representative chromatograms are shown of perfusates of Langendorff preparations and the working hearts of cats and rabbits. Remarkable differences were obtained before and after ischaemia and before and after treatment with a nucleoside transport inhibitor. Baseline separation of cytosine, orotic acid, cytidine, uracil, uric acid, hypoxanthine, xanthine, inosine, guanosine, xanthosine, allopurinol, thymine and adenosine was achieved. The detection limit for these compounds was less than 1 ng per injection.