Quantitative alterations of steroid urinary profiles associated with diabetes mellitus.

Capillary gas chromatography was used for the acquisition of quantitative metabolic profiles of urinary steroids from normal subjects and diabetic patients. Structures of 70 steroid metabolites have been assigned tentatively through mass spectrometry. Quantitative differences between the groups of normal and pathological samples (both males and females) are seen primarily for androsterone, etiocholanolone, dehydroepiandrosterone, 11-oxygenated 17-ketosteroids, corticosteroid metabolites, and a newly discovered metabolite, recently identified as a C26 pentol. The only significant difference between two different age groups of normal males was shown by androsterone.

Investigation of pharmaceutical high-performance liquid chromatography assay bias using experimental design.

This article presents a systematic approach to investigate, document, and eliminate pharmaceutical HPLC assay bias using experimental design. This is the first article to describe the application of experimental design in the area of assay bias. It is found that both formulation and analytical variables can contribute to pharmaceutical HPLC assay bias using model compounds and formulations.

Separation of diastereoisomers of DuP 105, a novel oxazolidinone antibacterial agent, by supercritical fluid chromatography on a Chiralcel OD column.

Oxazolidinones are a novel class of synthetic, orally-active antibacterial agents. DuP 105, which is representative of this class of compounds, is synthesized as a racemic mixture of two diastereoisomers. To ensure lot-to-lot consistency, separation and quantitation of these diastereoisomers is essential. Separation by reverse phase LC has not been achieved. This paper presents a supercritical fluid chromatography method using a Chiralcel OD column to resolve these diastereoisomers. A retention mechanism is briefly elaborated, based on the effects of temperature, pressure, percent modifier and type of modifier on resolution.

Comparison of liquid chromatography, capillary electrophoresis and super-critical fluid chromatography in the determination of Losartan Potassium drug substance in Cozaar tablets.

Reversed phase liquid chromatography, micellar electrokinetic chromatography, and packed column supercritical fluid chromatography were used to measure the amount of Losartan Potassium drug substance in pharmaceutical tablets. Tablet extract samples were analyzed and results were used to compare accuracy, precision, and linearity of calibration of the instrumental techniques. All three techniques have satisfactory precision (less than 1% RSD) and accuracy to be used for the analysis of the drug substance in tablets and the advantages of each technique are discussed.

Determination of a novel bile acid sequestrant in rodent diet by near-infrared spectroscopy.

DMP 504 is a high molecular weight polymer currently under development by The DuPont Merck Pharmaceutical Company as a novel bile acid sequestrant to lower serum cholesterol. To assess its safety, DMP 504 is incorporated into rodent diet for oral administration to rats and mice. An analytical method was developed to determine the accuracy and homogeneity of the blends. Since a physical separation or extraction of DMP 504 from the diet was not feasible, near-infrared spectroscopy (near-IR) was employed. The near-IR method provides accurate and precise results for blends containing 1.5-8.0% of DMP 504. Comparison of results at the 1.5% level with a cholate binding referee method is also presented. Both methods provided equivalent results for the 1.5% level.

Effects of starvation and refeeding on the excretion of urinary steroid metabolites in mice with different genetic background.

Gas chromatographic steroid metabolic profiling procedures have been applied to investigations of the effects of starvation and refeeding in mice. Urinary steroid metabolites were quantitatively followed during the starvation-refeeding experiments for mice with different genetic backgrounds. Some quantitative alterations were noted for certain congenic strains of mice. The metabolites which exhibited such quantitative variations were tentatively identified by means of combined gas chromatography-mass spectrometry.

New biochemical separations using precolumn derivatization and microcolumn liquid chromatography.

Microcolumn liquid chromatography with slurry-packed capillary columns has been used to resolve mixtures of biologically important steroids and prostaglandins. In order to enhance detection sensitivity, the samples are first derivatized with a suitable chromophore-yielding agent. Hydroxy steroids were derivatized with either benzoyl chloride or 7-(chlorocarbonylmethoxy)-4-methylcoumarin, while Dns hydrazine was employed to react with the ketonic groups of certain steroidal conjugates. Bile acids can also be derivatized with bromomethylcoumarin to yield fluorescent products. The use of microcolumns permits both a high degree of component resolution and enhanced detection sensitivity.

Degradation of a fluoropyridinyl drug in capsule formulation: degradant identification, proposed degradation mechanism, and formulation optimization.

The purpose of this paper was to investigate the degradation chemistry of a fluoropyridinyl drug candidate in capsule formulation and to optimize the formulation based on a proposed degradation mechanism. Small developmental batches of capsules were made by tituration of drug substance and excipients using a mortar and pestle, followed by manual encapsulation. Degradants were identified by LC-MS/MS and LC-photodiode array detector (PDA) and were monitored by LC-ultraviolet detector (UVD) during stability studies. It was found that the drug could undergo a nucleophilic substitution reaction in which hydroxyl groups replace the fluorine substituents on the pyridine rings. The initial degradation rate is independent of the drug concentration but dependent on the temperature, the pH of the microenvironment, and the excipient type. On the basis of these experimental results, a nucleophilic substitution reaction mechanism for the degradation was proposed and a successful capsule formulation was developed.