Perchlorate Buffer Research Articles

Enantiomeric separation of six 2-arylpropionic acids after pre-column derivatization with various amines and alcohols on a cellulose-based chiral stationary phase

A large number of mono-, bi- and tricyclic amines and alcohols were used for the derivatization of six 2-arylpropionic acids. The effect of the bonded aromatic portion on the enantiomeric separation using a tris(4-methylbenzoate)cellulose column was studied. Small modifications of the bonded groups close to the chiral centre pointed out their predominant steric effect to the chiral recognition process rather than electronic influence. Varying ratios of methanol and perchlorate buffer composing the mobile phase were applied to elute the different series within comparable analysis times.

Comparative Study on the Enantiomeric Separation of Several Non-Steroidal Anti-Inflammatory Drugs on Two Cellulose-Based Chiral Stationary Phases

Two cellulose-based chiral stationary phases were compared on their feasibility to resolve a representative number of 2-arylpropionic acids : a new experimental phase (Tolylcellulose, EXP B101) manufactured by Bio-Rad RSL and the Chiralcel OJ phase by Daicel. Both columns were tested under normal phase conditions, applying a n-hexane:isopropanol mobile phase. The Bio-Rad column was also assayed under reversed phase conditions using a methanol and perchlorate buffer system. Enantiomeric separation without prior derivatization of most 2-arylpropionic acids was far better on the Chiralcel OJ column than on the Bio-Rad column, the latter performing somewhat better under reversed phase conditions. Prior derivatization of the carboxylic acid group with an amine (naphthylmethylamine, (2-methyl)benzylamine) or an alcohol (benzylalcohol) permitted to separate the tested drugs to different extents on both columns.

Separation of 2-arylpropionic acids on a cellulose based chiral stationary phase by RP-HPLC

The enantiomers of eight 2-arylpropionic acids, a group of chiral non steroidal antiinflammatory drugs, were resolved as their benzylamide derivatives on a high-performance liquid chromatographic chiral stationary phase consisting of a covalently bound tris (4-methylbenzoate) cellulose layer on silica gel. The column was used under reversed-phase conditions using methanol as the main mobile phase component, with a perchlorate buffer pH 2.0. A compromise for derivatization with a water soluble carbodiimide and 1-hydroxybenzotriazole of a group of eight analytes was obtained. The derivatives were identified by IR- and MS-spectroscopy.

Simultaneous determination of tropatepine and its major metabolites by high-performance liquid chromatographic—mass spectrometric identification : Application to metabolic and kinetic studies

Tropatepine is used to combat against extrapyramidal syndrome induced by neuroleptic drugs. A high-performance liquid chromatographic method was proposed for the simultaneous determination of tropatepine and its potential metabolites in biological fluids. After double extraction of compounds in hexane and back-extraction in hydrochloric acid, the chromatographic separation was performed on a reversed-phase column with an acetonitrile—perchlorate buffer mixture as mobile phase. Compounds were detected at 229 nm and the detection limit was about 15 ng/ml. The method was applied to bile and urine samples collected in rats, after a single high oral dose of 100 mg/kg of tropatepine hydrochloride. Gas chromatography—mass spectrometry was used for identification of the potential metabolites. Nortropatepine and tropatepine S-oxide were identified in this way, and it seemed that tropatepine was subjected to a large and intense metabolic process. The analytical procedure and the results of the metabolic investigation were applied to a preliminary pharmacokinetic study in patients undergoing long-term oral therapy with tropatepine.

Studies on the reaction of aromatic bases with epoxides, and anucleophilic buffer for the acid-catalysed hydrolysis of epoxides

The rates of nucleophillic reaction of pyridine and pyrazine with propylene and isobutylene oxides have been measured and compared with related data. No nucleophilic activity can be detected for tetramethylpyrazine, and this base forms an effective buffer in the pH range 3–4. A precision of 3–4% may be attained when rates of epoxide hydrolysis are measured in tetramethylpyrazine–perchlorate buffer solutions at pH 3·5. The rate coefficient for the acid-catalysed hydrolysis of 0·1M-aqueous isobutylene oxide at 25·7° is within the range 7·35 ± 0·24 I mol–1 s–1.