Jean-Paul Bounine

Optimization of the instrumental parameters of a combined liquid chromatograph–mass spectrometer, coupled by an interface for direct liquid introduction : IV A new desolvation chamber for droplet focusing or townsend discharge ionization

Abstract A new desolvation chamber has been coupled to a liquid chromatograph-mass spectrometer interface. The shape of the drift tube was designed to focus the electrically charged droplets from the diaphragm nebulizer into the chemical ionization source. A voltage applied to the desolvation chamber influenced both the total ion current and the relative abundance of the ions when constant flow-rates of acetonitrile were nebulized. A stable but unsustained Townsend discharge occurred when the voltage on the desolvation chamber was above 140 V.

Isohydric solvents in liquid-solid column chromatography : Importance for the reproducibility of chromatographic separations and application to the experimental determination of mobile phase polarity

Abstract Isohydric solvents are defined as solvents with water contents corresponding to the same activity of the adsorbent. The influence of the water content of the mobile phase on the activity of the adsorbent and on the reproducibility of separations was studied. A practical means of determining suitable water contents of solvents and solvent mixtures is described. The use of isohydric solvents greatly improves the reproducibility of chromatographic separations. The water contents of isohydric solvents may constitute a scale of relative polarities. In mixtures of isohydric solvents, good linear relationships were obtained between solute capacity factors (k′) and the inverse of the molar fraction of water (1/NH2Oisoh).

Adsorption liquid chromatography on columns : A rational method of mobile phase optimization based on the use of isohydric solvents

Abstract In order to facilitate the use and automation of liquid column chromatography in control laboratories, we have made a classification and a rational combination of solvents. By using an experimental determination of polarity, based on the water content of previously defined isohydric solvents, we have elaborated a method for the optimization of separations that considerably reduces the operating time, gives a more accurate description of processes and greatly limits the number of systems able to solve most of the problems. Practical separations of drug formulations, barbiturates, aromatic bases and phenothiazines are considered.

High-performance liquid chromatographic stability-indicating determination of zopiclone in tablets

Abstract A high-performance liquid chromatographic method was developed for the determination of zopiclone in pharmaceutical tablets. The ion-pair reversed-phas

Spherosil for high-performance, moderate-pressure liquid chromatography

Abstract The aim of this study was to prove experimentally that an inexpensive high-performance liquid chromatography system for routine control, operating at moderate pressures as predicted by the theoretical optimization model of Martin, Eon and Guiochon, is feasible. Two improved types of Spherosil, XOA 600 and XOA 800, lead to better selectivities and efficiencies (800 plates/cm), short columns (5–10 cm), that can be operated at moderate pressures (10–30 bar) and reasonable analysis times (5–15 min). The low pressure drops are due mainly to: the spherical shape of the particles, an average particle diameter of 5–7 μm, a narrow particle-size distribution (90% of the fraction between the limits d p ± 2 μm), a high specific surface area (600 or 800 m 2 /g) (the larger the surface area the shorter is the column and consequently the lower the pressure drop) and the linear velocity of the mobile phase fixed at the minimum of the Van Deemter curve. Numerous examples of separations confirm the potential of this new trend in high-performance liquid chromatography.

Development and validation of a high-performance liquid chromatographic stability-indicating method for the analysis of Synercid® in quality control, stability and compatibility studies

A gradient high-performance liquid chromatographic (HPLC) method was developed for the analysis of Synercid freeze-dried powder in routine quality control, stability and compatibility studies. This method is suited for a simultaneous assay of drug substances and impurities. The method was validated for precision, reproducibility, linearity, accuracy and limits of detection. The robustness study that was performed according to an experimental design is described.