Analysis of combinatorial chemistry samples by micellar electrokinetic chromatography.

A micellar electrokinetic chromatography (MEKC) method has been developed that can evaluate the purity of samples generated in combinatorial chemistry libraries. This method uses an open tube capillary (27 cm x 50 microm) along with a run buffer composed of sodium dodecyl sulfate (SDS), hydroxypropyl-beta-cyclodextrin, and sodium tetraborate coupled with UV detection. Neutral compounds and compounds that were insoluble in aqueous buffers could be analyzed under these conditions in approximately 3 min. The concentration of SDS and the concentration of hydroxypropyl-beta-cyclodextrin effected the separation. The affect on selectivity resulting from the addition of an organic modifier to the run buffer was examined. The low background absorbency of the run buffer made for easy detection of compounds that absorbed at low UV wavelengths. The quick analysis time made this suitable for analysis of combinatorial chemistry samples.

Quantitative determination of dipalmitoylphosphatidylcholine and palmitic acid in porcine lung surfactants used in the treatment of respiratory distress syndrome.

A high-performance liquid chromatography (HPLC) method was developed that can separate and quantify dipalmitoylphosphatidylcholine and its degradation product, palmitic acid from various phospholipids contained in a porcine lung surfactant used in the treatment of respiratory distress syndrome, which was recently approved for use by the FDA. The method used a C8 reversed-phase HPLC column with a (50:45:10) acetonitrile/methanol/acetic acid mobile phase, and refractive index detection. The active component of the lung surfactant, dipalmitoylphosphatidylcholine (DPPC) and palmitic acid (PA), could be quantified following a liquid-liquid extraction procedure along with an internal standard, dimyristoylphosphatidylcholine (DMPC). The assay was validated for linearity, accuracy, precision, reproducibility and ruggedness. Column stability was measured by performing the assay over time and monitoring the system suitability parameters. The extraction procedure has a 90% recovery and the assay is linear over a range of 5 microg/ml to 300 microg/ml. The assay is used to release commercial product and monitor stability of existing lots of material.

The separation of ipratropium bromide and its related compounds.

Ipratropium bromide, the active component in ipratropium bromide metered dose inhalers (MDI), is used as a bronchodilator for the maintenance and treatment of bronchospasms associated with chronic obstructive pulmonary disease (COPD). The separation of ipratropium bromide, tropic acid, N-isopropyl-nor-atropine (NINA), 8-s ipratropium bromide, apo-ipratropium bromide and the excipients found in the formulation is important for analyzing raw materials and stability samples. We now report a reversed-phase HPLC method that can be used for separating ipratropium bromide and its related compounds, using an acetonitrile/potassium phosphate buffer (100 mM, pH 4.0) gradient mobile phase. Previous methods used for separating ipratropium bromide from its related compounds involved reversed-phase ion-pairing HPLC with UV detection. These methods exhibited less reproducibility, less ruggedness and required a high flow rate. The reported method is linear from 10 to 1000 micrograms ml-1 with a limit of detection of 60 ng ml-1. In addition, analysis of samples subjected to accelerated stability conditions showed that all degradants are resolved from the active component, resulting in stability-indicating assay. This assay also saved mobile phase and eliminated problems associated with ion-pairing reagents.

The structural analysis of a levan produced by Streptococcus salivarius SS2.

The structure of a water-soluble levan produced by Streptococcus salivarius SS2 has been determined by means of various chemical and instrumental methods. Methylation and periodate oxidation studies demonstrate that the levan is comprised of D-fructofuranosyl backbone residues linked beta-(2----6) (about 70%) with beta-(2----1) branches (about 30%). 13C-N.m.r. spectral analysis of the polymer is consistent with the structure determined by chemical means.