Bfh Drenth

Determination of cyclodextrins in biological fluids by high-performance liquid chromatography with negative colorimetric detection using post-column complexation with phenolphthalein

A rapid and sensitive high-performance liquid chromatographic method for the analysis of beta- and gamma-cyclodextrin in aqueous biological fluids such as plasma, urine, or tissue homogenate is described. The chromatographic system consists of a microBondapak Phenyl column as stationary phase and a mobile phase of water with 10% methanol. After post-column addition of an alkaline solution of phenolphthalein, negative colorimetric detection is used. The elution solvent and post-column reagent were mixed in a capillary tubing of 1.5 m (1.0 mm I.D.). Two methods of sample treatment are given, one for large (1.0 ml) and one for small (0.1 ml) sample volumes. Both methods were shown to be linear and reproducible. The detection limit for beta-cyclodextrin was 1.0 microgram/ml (0.77 nmol/ml). The method was used in the determination of some pharmacokinetic parameters of beta-cyclodextrin in rats after intravenous injection.

A study of the separation of enantiomers of some aromatic carboxylic acids by high-performance liquid chromatography on a β-cyclodextrin-bonded stationary phase

Abstract The enantiomers of some aromatic carboxylic acids of biomedical interest were separated by high-performance liquid chromatography on a β-cyclodextin-bonded stationary phase. Evaluation of the system shows that the structure of the acids plays an important role in the possibility for separation of the enantiomers. Moreover, the pH as well as the buffer components of the mobile phase have a pronounced effect on the retention times and the selectivity of the system. In order to reduce tailing, the column temperature was increased; this resulted in better peak resolution. Anomalous behaviour was seen in the relation between retention time and sample concentration. At low amounts of injected sample the retention times increased, but this could not be ascribed to adsorption processes. This phenomenon caused great problems in the quantitative analysis of the two enantiomers with this system.

COMPARISON OF 2 BETA-CYCLODEXTRIN BONDED STATIONARY PHASES FOR HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY - ELUTION ORDER AND OPTICAL PURITY OF ENANTIOMERS OF CYCLOHEXYLPHENYLGLYCOLIC ACID

Comparaison entre colonne du commerce et du laboratoire, et entre mesure de purete optique par chromatographie ou calorimetre differentielle a balayage

The metabolic fate of the dopamine agonist 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin in rats after intravenous and oral administration II. Isolation and identification of metabolites

1. The in vivo metabolic pathways of 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin (I) in rats have been established, using in vitro metabolism as a complementary technique. 2. All identified metabolites were conjugates. Glucuronidation at the phenolic group yields the major metabolite, accounting for 50% (i.v.) or 65% (oral) of the dose. The corresponding sulphate conjugate of I is virtually absent (less than 0.2% dose). 3. Hydroxylation of I, at the ortho position to the phenolic hydroxy group, yields 6-hydroxy-I (II), accounting for about 13% (i.v.) or 9% (oral) dose. This catechol is excreted, as a glucuronide, almost exclusively into the bile. Both the 5- and the 6-glucuronide of II were detected in about equal amounts. 4. Metabolism of I in vitro showed that under oxidative conditions, depropylation of I occurred. Conjugation of 3H-I in the presence of UDPGA or PAPS, was successful in yielding the glucuronide and sulphate conjugates.

Determination of clomipramine and desmethylclomipramine in plasma by means of liquid chromatography.

A method is presented for the determination of clomipramine and its major metabolite desmethylclomipramine in plasma. After extraction with n-hexane, the components are separated by high performance liquid-solid chromatography on silica gel and detected with a UV detector. The detection limits are 2 ng/ml for clomipramine and 10 ng/ml for desmethylclomipramine. Recoveries from plasma exceed 95% for both drugs. In routine analysis, 30-40 samples can be handled in one day. The practical use of the method is shown in plasma concentration-time curves after oral and intramuscular administration of clomipramine.

The metabolic fate of the dopamine agonist 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin in rats after intravenous and oral administration I. Disposition and metabolic profiling

1. The disposition and metabolic profiling of 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin(I), a dopamine agonist, were studied in anaesthetized rats after i.v. administration and in non-anaesthetized rats after i.v. and oral dosing. No major differences due to narcosis were observed. 2. Independent of dosing route or anaesthetic, clearance of I was rapid. Bile was the main route of excretion, accounting for 88% dose, compared with 9% in urine. 3. Drug metabolic profiling revealed that I is almost completely metabolized before elimination; less than 0.5% total radioactivity in bile and urine was due to parent compound. 4. The biliary metabolic profiles after i.v. and oral administration were similar. One major metabolite was detected, accounting for 50% (i.v.) or 65% (oral) dose. The major biliary metabolite was identified as the glucuronide of I. 5. Urinary metabolic profiles were quantitatively different from those of bile. After i.v. administration one major metabolite was detected in urine, but this was not the major biliary metabolite. After oral administration, the major urine metabolite was the same as the major biliary metabolite. These differences can be explained by first-pass gastro-intestinal metabolism.

UNIVERSAL, MULTI-CHANNEL ULTRAVIOLET DETECTION IN THE PURITY ANALYSIS OF 2-ETHYL-3-(4-HYDROXYBENZOYL)INDOLIZINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Abstract The use of a multi-channel UV—visible detector coupled with high-performance liquid chromatography in purity analysis is decribed. A discussion of some advantages and disadvantages in comparison with a conventional (single-wavelength) UV detector is given. Detection and identification limits for a particular contaminant of 2-ethyl-3-(4-hydorxybenzoyl)indolizine are determined. Sensitivities for both detectors with regard to the same contaminant are derived from the calibration curves.

On-line diode array UV-visible spectrometry in screening for drugs and drug metabolites by high-performance liquid chromatography.

The direct coupling of a multi-channel diode array UV-visible spectrophotometer to a powerful reversed-phase HPLC separation system is considered, especially for use in qualitative analysis, e.g., screening/identification of drugs and drug metabolites. The approach is illustrated by the screening for metabolites of butoprozine and ticlopidine directly in human and rat bile.

PERCUTANEOUS-ABSORPTION, METABOLISM, AND ELIMINATION OF THE PENETRATION ENHANCER AZONE IN HUMANS AFTER PROLONGED APPLICATION UNDER OCCLUSION

Azone was applied undiluted to an extended area of the forearm and left in place for 12 h under occlusion in 3 volunteers. Azone was found to be absorbed in very low amounts (0.419 ± 0.259% of the applied dose) and accumulation in the body did not occur. As compared to a previous study, the new application conditions gave an increase in amount and percentage absorbed, but a decrease in flux. Absorbed material was excreted rapidly and almost exclusively through the urine after extensive metabolism to at least 3 rather polar compounds. These findings and the absence of treatment-related side-effects in the 3 volunteers suggest azone to be safe for human use when topically applied under occlusion.

Determination of enantiomeric purity of the new D-2 dopamine agonist 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin (N-0437) by reversed-phase high-performance liquid chromatography after pre-column derivatization with D(+)-glucuronic acid.

This paper describes an enzymic derivatization procedure that allows accurate determination of very small amounts of enantiomeric impurities in the D-2 dopamine agonist 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin (N-0437). After pre-column glucuronidation of the individual enantiomers, two diastereoisomers were formed which were separated by reversed-phase high-performance liquid chromatography. An enantiomeric purity of 99.84% was calculated for the (-)-enantiomer, against 99.89% for the (+)-enantiomer. The assay was validated by spiking 1% of the (-)-enantiomer in the (+)-enantiomer. A high accuracy (error 4.5%) and precision (coefficient of variation 2.9%, n = 5) of the method were established.