Chiral separations of transition metal complexes using capillary zone electrophoresis.

Several buffer additives that may facilitate chiral separation for optically active transition metal (TM) systems are investigated using capillary zone electrophoresis. The TM complexes evaluated exhibit considerable heterogeneity with respect to total complex charge (0 to 4+), ligand type, and identity of the central metal including Ru2+, Ni2+, Cr3+, and Co3+, threo-D[+]-Isocitrate, potassium antimonyl-d-tartrate and dibenzoyl-L-tartrate are identified as the most efficient chiral selectors. Interestingly, TM complexes exhibiting a (3+) total complex charge exhibit a reversal of enantiomer elution order versus all other complexes when separated using the tartrate additives. Operating parameters including pH, temperature, and capillary length are discussed, and chiral separations of complex mixtures are demonstrated.

Hydrophobic interaction electrokinetic chromatography for the separation of polycyclic aromatic hydrocarbons using non-aqueous matrices.

Capillary electrophoresis methodology is developed to provide a rapid, inexpensive and robust technique for screening polycyclic aromatic hydrocarbons (PAHs) in water using additive complexation. A series of conventional RPLC ion-pairing agents are investigated in three different totally non-aqueous separation solvents, and the relative role of hydrophobic interaction versus electrostatic association is evaluated. Methanol is found to provide optimal selectivity when coupled with the tetrahexylammonium cation providing total analysis times of approximately 15 min for the analysis of thirteen 2-7-ring PAH pollutants. Solid-phase microextraction is demonstrated to be an effective sample preparation technique for extraction/preconcentration of PAHs from water into methanol run buffer prior to injection.

Innovative techniques in lower extremity revascularization.

Revascularization of the ischemic foot remains a significant challenge for even the most experienced vascular surgeons. Lower extremity revascularization can be accomplished by endarterectomy, endovascular techniques, or bypass. In experienced hands, excellent results have been reported with endarterectomy. However, this technique has limited application because of the diffuse nature of infrainguinal atherosclerotic disease. Endovascular techniques, such as atherectomy and laser-assisted balloon angioplasty, gained enormous popularity initially because they were less invasive than standard techniques. Unfortunately, the long-term results with these techniques have been disappointing.

Phase transitions of reversed-phase stationary phases. Cause and effects in the mechanism of retention.

We provide a somewhat historical perspective on the work that has been accomplished that supports the suggestion of phase transitions in reversed-phase liquid chromatographic bonded phases. In addition to this general review, we consider from both a practical and theoretical viewpoint the implications of such transitions in the rational design of improved reversed-phase separations. Analytical theory and molecular simulation approaches to chromatographic stationary phases and related systems are reviewed. Initial results are presented on the temperature, density and chain length dependences of stationary phase properties. The role of computer simulation in analyzing transition behavior and retention processes is discussed.

Determination of metabolically derived nitroprocainamide in the urine of procainamide-dosed humans and rats by liquid chromatography with electrochemical detection.

The N-oxidized metabolites of the antiarrhythmic procainamide have previously been implicated as inciting agents in the autoimmune condition drug-related lupus. Although much data have been collected with respect to the in vitro behavior of these metabolites, relatively little has been accomplished in vivo because of their extreme reactivity. The determination of nitroprocainamide (NPA), a stable decomposition product of the reactive hydroxylamine and nitroso species, in the urine of rats dosed with procainamide is reported here using the sensitive and selective method of HPLC with electrochemical detection. For orally and i.v.-dosed animals, up to microgram amounts of NPA were excreted over 24 hr from an initial dose of 66-100 mg procainamide/kg body weight. Also, the apparent elimination of microgram quantities of NPA in the urine specimens of 9 of 11 patients undergoing treatment with procainamide was observed. This suggests that N-oxidation of the aromatic ring of procainamide is occurring at sufficient levels to result in the formation of significant amounts of the reactive hydroxylamine and nitroso metabolites in vivo, and may have direct implications in the diverse and widespread symptomatology associated with procainamide-induced drug-related lupus.

Effects of procainamide hydroxylamine on generation of reactive oxygen species by macrophages and production of cytokines.

A series of experiments was conducted to examine the effects of the N-oxidized metabolite of procainamide, procainamide hydroxylamine (PAHA), on reactive oxygen species (ROS) production by macrophages in vitro, as well as on the release of the cytokine interleukin-1 (IL-1). Results with PAHA were compared with those from the parent compound, procainamide, and in some cases with other procainamide metabolites such as N-acetylprocainamide or nitrosoprocainamide. The effects of PAHA on ROS production by mouse and rat macrophages were complex, resulting in both stimulatory and inhibitory activity depending upon the PAHA concentration and whether macrophages were resting or elicited. The primary effect of PAHA appeared to be a stimulation of ROS production. Monocytes pretreated with PAHA (20 microM) depressed the responsiveness of lymphocytes in co-culture to a T-cell mitogen (conconavalin A) but not a B-cell mitogen (lipopolysaccharide). This effect was inhibited when monocyte pretreatment with PAHA was accompanied by the antioxidants, catalase or superoxide dismutase. IL-1 production by rat adherent splenocytes was unaffected by PAHA in concentrations that were not cytotoxic. These observations suggest that the oxidative metabolism of procainamide to PAHA may result in enhanced production of ROS by macrophages contributing its toxicity to lymphocytes.

Electrochemical investigations of immunologically reactive procainamide metabolites.

As a result of the implication of N-oxidized procainamide metabolites in drug-related lupus (DRL), the electrochemical behaviour of these compounds was investigated and a coulometric synthesis of the nitroso derivative developed using a previously described carbon packed bed bulk electrolysis flow cell. The electrochemical characterization of the parent p-substituted aromatic amine and the N-oxidized derivatives was achieved through systematic comparison with previously well described aromatic amine and nitro systems using cyclic voltammetry and liquid chromatography with electrochemical detection (LC-EC). Chromatographically assisted hydrodynamic voltammetry indicated current limiting plateau potentials of 0.45 and -0.2 V versus Ag/AgCl, respectively, for synthetically prepared procainamide hydroxylamine and electrolytically prepared nitrosoprocainamide. Reaction characterization and binding behaviour is described for each of the procainamide metabolites following in vitro incubations with cysteine, glutathione, ascorbic acid and mouse haemoglobin.

Electrochemical determination of N-oxidized procainamide metabolites and functional assessment of effects on murine cells in vitro.

Because of the implication of N-oxidized metabolites of procainamide in the induction of drug-related lupus, we have studied the electrochemical behavior of these metabolites and developed an electrochemical synthesis of nitrosoprocainamide. This synthesis was developed using procainamide hydroxylamine as the starting material which was oxidized to the nitroso species at an applied potential of 700 mV vs Ag/AgCl using a carbon packed bed bulk electrolysis flow cell. Conversion efficiencies of greater than 95% were achieved with this method. Subsequent studies with a chemically diverse series of biocompounds were used to investigate possible reactions between the procainamide hydroxylamine and nitroso species and these selected molecules. Only antioxidants such as cysteine, glutathione and ascorbic acid were found to react with the nitroso compound as determined by electrochemical methods, and this reaction was characterized as primarily a simple redox reaction at physiological pH. Animal studies conducted with murine spleen cells incubated with mitogens and various procainamide compounds demonstrated that the N-oxidized metabolites are the active immunopharmacologic agents.