HPLC method for determination of 3,4-diaminopyridine in the presence of related substances and degradation products formed under stress conditions

3,4-Diaminopyridine is used to treat some symptoms met in Lambert Eaton myasthenia syndrome. It was shown efficient to reduce a form of variable muscle weakness and fatigability typical of the disease and correlated to a block of acetylcholine release. A high performance liquid chromatographic method for the determination of 3,4-diaminopyridine in the presence of related substances and its degradation products is described. The method is based on the use of a C18 bonded phase column and a mobile phase composed of 10 volumes of acetonitrile and 90 volumes of an aqueous solution containing 1 g L-1 sodium octanesulfonate and 0.77 g L-1 ammonium acetate. The pH of the aqueous solution was adjusted to 1.9 with trifluoracetic acid. All peaks are eluted in <40 min. The method was demonstrated to be precise, accurate and specific even though a major part of the drug is decomposed. The results indicate that the proposed method could be used in stability assays. © 2006 Friedr. Vieweg & Sohn/GWV Fachverlage GmbH.link_to_subscribed_fulltex

Sensitive quantification of diphemanil methyl sulphate in human plasma by liquid chromatography-tandem mass spectrometry

A simple detection system with a high-performance liquid chromatography (HPLC) with positive ionisation-tandem mass spectrometry (ESI-MS/MS) for determining diphemanil methylsulphate (DMS) levels in human plasma using 4-diphemanylmethylene,1-methylpiperidine as an internal standard (I.S.), is proposed. The acquisition was performed with the multiple reactional monitoring (MRM) mode, by monitoring the transitions: m/z 278 > 262 for DMS and m/z 263 > 247 for the I.S. The method involved a simple single-step deproteinisation with acetonitrile. The analyte was chromatographed on a Zorbax® C18 reversed-phase chromatographic column by isocratic elution with 10-3 M ammonium acetate and 10-3 M hexafluorobutyric acid, adjusted to pH 7.0 with ammoniac/acetonitrile (40/60, v/v). The results were linear over the studied range (0.5-50.0 ng mL-1) and the total analysis time for each run was 10 min. The mean extraction apparent recoveries expressed at the 95% intervals of confidence were 94-104% for DMS and 92-106% for the I.S. The intra- and inter-assay precisions were 4.6-8.4% and 2.9-10.6%, respectively. The limit of quantification was 0.15 ng mL-1. The devised assay was successfully applied to the residual concentrations monitoring in infant. © 2006 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

Determination of A 3,4-diaminopyridine in plasma by liquid chromatography with electrochemical detection using solid-phase extraction

In order to quantify a small amount of a drug, 3,4-diaminopyridine (3,4-DAP), in animal plasma samples, an analytical method was developed. It involved an extraction of 3,4-DAP and phenylephrine, used as internal standard (IS), from plasma with solid-phase extraction (SPE) on C18 cartridges. This analytical method is a hyphenated technique based on high-performance liquid chromatography with electrochemical detection (HPLC-EC) whose purpose is to obtain first a sensitive method and second a satisfying separation between 3,4-DAP and phenylephrine. The analytical method is accurate, specific, and linear between 10 and 500 μg of 3,4-DAP per litre. The recovery of 3,4-DAP is estimated at 70.8% with a 95% confidence interval of (66.0-75.6%). Intermediate precision was evaluated on three quality control samples; the intra-day precision was estimated at 13.5, 9.1, 7.8% and the inter-day precision at 17.9, 8.4, 9.3%. The limit of quantification of the method was evaluated at 10 μg l-1. First toxicokinetic parameters determined on dogs plasma samples after one 3,4-DAP oral administration of 1 mg kg-1 were: C max=395.7 μg l-1; Tmax=15 min; t 1/2=113.6 min; Clearance/F=16.8 ml kg-1 min-1 and Vd/F=2.7 l kg-1. © 2004 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex