GLC determination of warfarin in human plasma

Developing a GC-EI-MS/MS method for quantifying warfarin and five hydroxylated metabolites generated by the Fenton reaction

Since the 1950s, Warfarin has been used globally as both a prescription drug and a rodenticide. Research has shown that warfarin and other rodenticides are present in the environment and food chain. However, emerging contaminants are subject to degradation by biotic and abiotic processes and advanced oxidation processes. In some cases, detecting the parent compound may not be possible due to the formation of structurally changed species. This approach aims to identify hydroxylated transformation products of warfarin in a laboratory setting, even after the parent compound has undergone degradation. Therefore, the Fenton reaction is utilized to insert hydroxylation into the parent compound, warfarin, by hydroxyl and hydroperoxyl radicals generated by Fe2+/Fe3+ redox reaction with hydrogen peroxide. Using multiple reaction monitoring, a GC-MS/MS method, incorporating isotopically labeled reference compounds, is used to quantify the expected derivatized species. The analytes are derivatized using trimethyl-3-trifluoromethyl phenyl ammonium hydroxide, and the derivatization yield of warfarin is determined by using isotopically labeled reference compounds. The method has a linear working range of 30 to 1800 ng/mL, with detection limits ranging from 18.7 to 67.0 ng/mL. The analytes are enriched using a C18-SPE step, and the recovery for each compound is calculated. The Fenton reaction generates all preselected hydroxylated transformation products of warfarin. The method successfully identifies that 4'-Me-O-WAR forms preferentially under the specified experimental conditions. By further optimizing the SPE clean-up procedures, this GC-MS-based method will be suitable for detecting transformation products in more complex matrices, such as environmental water samples. Overall, this study provides a better understanding of warfarin's degradation and offers a robust analytical tool for investigating its transformation products.

Electrooxidation of iodide in the presence of 4-hydroxycoumarin: application to a simple coulometric titration of 4-hydroxycoumarin

The electrochemical oxidation of iodide ion in the presence of 4-hydroxycoumarin (1) was studied using cyclic voltammetry and controlled-potential coulometry. The result indicates that the resulting iodine takes part in a halogenation reaction and reacts with 4-hydroxycoumarin (1). According to the obtained results, a new and simple coulometric titration method with potentiometric end-point detection for the determination of 4-hydroxycoumarin (1) is presented. In the presented method, 2-200 micromol of 4-hydroxycoumarin (1) was successfully determined.

Determination of warfarin in drinking water by high-performance liquid chromatography after solid-phase extraction

A method for the determination of 0.1 micrograms/l of warfarin in drinking water involving concentration by solid-phase extraction is described. A 1000-ml volume of drinking water is aspirated through a solid-phase extraction column and warfarin is eluted to 1.0 ml. The eluate is analysed by reversed-phase high-performance liquid chromatography with UV detection. The detection limit is 0.02 micrograms/l. Recoveries of greater than 90% were obtained when tap water was spiked with warfarin.

Drug level monitoring: chromatography of some minor groups of drugs

Some important facts about the chromatographic separation of a number of selected categories of drugs are summarized. The data refer to the chromatographic method of choice, stationary phase, mobile phase (carrier gas), detection procedure and (where available) method sensitivity. Also, fundamental instrumental parameters, namely injector, column and detector temperature, carrier gas and mobile phase flow-rate and gradient set-up are reported here. In all cases also the source material used for analysis is specified. The data are presented in table form, each table dealing with a particular category of drugs. The following categories of drugs are being dealt with: anthelmintics, antiarteriosclerotics, antibacterials, anticholinergics and cholinergics, anticoagulants, antidiabetics, antiemetics, antimycotics, antihistamines, antimalarials, antiparasitics, antiparkinsonics, antitussives, antiulcer drugs, antiviral compounds, appetite depressants and immunosuppressives.

High-performance liquid chromatographic strategies for the determination and confirmation of anticoagulant rodenticide residues in animal tissues

A comprehensive approach to the analysis of anticoagulant rodenticide residues in animal tissues based on high-performance liquid chromatography (HPLC) has been developed. Residues of warfarin, coumatetralyl, difenacoum, brodifacoum, bromadiolone, diphacinone and chlorophacinone were extracted with chloroformacetone (1:1, v/v). Extracts were cleaned-up by an integrated gel permeation and adsorption chromatographic procedure which divided the rodenticides into two groups. Residues were then determined and confirmed using normal-phase, ion-pair and weak ion-exchange HPLC techniques. Ion-pair gradient separation resolved all seven rodenticides in a single chromatographic analysis. UV detection methods were employed for all seven rodenticides. Use of a diode array detection system permitted additional confirmation of residues down to 0.1 mg kg-1 by matching UV spectra and derivatives of spectra. Sensitive fluorescence detection was possible for the coumarin-based rodenticides but not for diphacinone and chlorophacinone. Post-column pH-switching fluorescence detection methods were shown to be superior to other methods of fluorescence detection of coumarin-based rodenticides. Recoveries from spiked liver tissue were around 90% at levels from 0.05 to 1 mg kg-1. Detection limits of around 0.002 mg kg-1 for most rodenticides and of 0.01 mg kg-1 for warfarin could be achieved with animal tissue extracts.

Comparison of the bioavailabilities and anticoagulant activities of two warfarin formulations

Changes in the British Pharmacopoeia dissolution time requirements have necessitated reformulation of warfarin sodium ('Marevan'). The old and new formulations were compared with each other in eight healthy volunteers given a single 15 mg dose of each in a cross-over study and also in 19 patients receiving warfarin therapy. In the volunteer study, a significant but small increase in bioavailability was observed for the new formulation. However, the effects of the two formulations on the prothrombin ratio and on clotting factors II, VII, IX and X were not significantly different. Irrespective of formulation, the greatest changes in factors II, VII and X were observed after the first dose of warfarin. With factor IX, the greatest response was observed after the second dose. The clinical study in patients confirmed that the old and new formulations of Marevan are interchangeable on a dose for dose basis. A sensitive semi-automated warfarin assay technique is described.