Rapid and sensitive high-resolution procedure for digitalis glycoside analysis by derivatization liquid chromatography

Preconcentration of digoxin using a synthetic imprinted polymer deposited upon the surface of double-layered hydroxides on porous anodised aluminium wire a triple solid-phase microextraction fibre

INTRODUCTION

A new solid-phase microextraction fibre is fabricated through polymerisation of molecularly imprinted polymer on the surface of a layered double hydroxide framework that has been fabricated via the in situ synthesis on a non-porous anodic aluminium oxide/aluminium wire as both the substrate and the aluminium source.

OBJECTIVE

The synthesized SPME fiber was performed to analyze trace digoxin in real samples.

MATERIAL AND METHOD

A one-at-a-time optimization strategy was applied for optimizing the important extraction parameters such as extraction solvent, extraction time, stirring rate, pH, ionic strength, and desorption time.

RESULT

Aluminum surface before and after anodizing and LDH structure reveal that anodizing and preparation LDH increases the surface area and adsorption capacity of aluminum wire.

CONCLUSION

Under optimum conditions, the repeatability for one fibre (n = 3), expressed as relative standard deviation (RSD %), was 5.2%.

Determination of amiprilose in human plasma by high-performance liquid chromatography with fluorimetric detection

A reversed-phase HPLC method to quantify amiprilose in human plasma is described. The method involves liquid-liquid extraction of amiprilose and the internal standard from plasma. The extracted compounds are derivatized with 1,8-naphthalic dicarboxylic acid using 2-chloro-1-methylpyridinium iodide as a coupling reagent. The derivatized products are separated on a reversed-phase column and monitored fluorimetrically using 280 nm and 340 nm as excitation and emission wavelengths, respectively. The derivatized products which exhibit two peaks on chromatogram, are shown to be the interconvertible isomers. This assay has been used in pharmacokinetic studies of amiprilose in humans.

High-performance liquid chromatographic determination of alpha-acetyldigoxin in Digitalis lanata leaves

An analytical method for the determination of alpha-acetyldigoxin in Digitalis lanata leaves by HPLC has been developed. The procedure consists of extraction of dry leaf powder with 50% methanol and cleanup by a Sep-Pak C18 cartridge prior to HPLC analysis. The quantitation is carried out by the incorporation of beta-methyldigoxin as an internal standard. HPLC is performed on an octylsilyl bonded silica column with acetonitrile/methanol/water (100/11/188, v/v). The effluent is monitored by uv absorption at 220 nm. The amount of alpha-acetyldigoxin per 100 mg of dry leaf powder is estimated at 5.55 +/- 0.21 micrograms (mean +/- SD). The average recovery of alpha-acetyldigoxin from added samples is 97.2%. The present method is sensitive, reliable, and relatively simple. Application of this HPLC method to the analysis of samples obtained by fermentation of the leaf powder is also demonstrated.

Electrochemical detection of the 3,5-dinitrobenzoyl derivative of digoxin by high-performance liquid chromatography

Electrochemical detection of 3,5-dinitrobenzoyl derivatives of digoxin and its metabolites following high-performance liquid chromatography is reported. Partial resolution of derivatized digoxin and dihydrodigoxin was obtained using a Spherisorb ODS II analytical column. Both single- and dual-electrode detection were investigated and a maximum sensitivity equivalent to 0.39 ng of digoxin was found with the dual-electrode method. This system has the necessary sensitivity and selectivity for development into a therapeutic monitoring assay method.

High-performance liquid chromatographic determination of secondary cardiac glycosides in Digitalis purpurea leaves

An analytical method for the determination of secondary cardiac glycosides in Digitalis purpurea leaves by high-performance liquid chromatography (HPLC) is described. The procedure consisted of extraction of dry leaf powder with ethanol-chloroform (2:1) and clean-up by Sep-Pak cartridges prior to HPLC analysis. HPLC was performed on an octylsilyl bonded silica column, using acetonitrile-methanol-water (4:4:5) for trisdigitoxosides and acetonitrile-methanol-water (8:30:43) for strospeside; the effluent was monitored by ultraviolet detection (at 220 nm). Quantitation of these cardiac glycosides was carried out by the internal standard method. The amounts of digitoxin, gitoxin, gitaloxin and strospeside per 100 mg of dry leaf powder were estimated to be 22.6, 14.0, 54.7 and 1.9 micrograms, respectively. The method is sufficiently sensitive and reproducible to assay secondary glycosides in Digitalis purpurea leaves.

Analysis of digoxin at therapeutic concentrations using high-performance liquid chromatography with post-column derivatization

A high-performance liquid chromatographic (HPLC) procedure has been developed for the analysis of digoxin in plasma at therapeutic concentrations. The assay method provides resolution of digoxin from its metabolites using a 15 cm X 4.6 mm HPLC column containing 3-micron octadecylsilane-bonded stationary phase. The effluent of the column is passed through a post-column reactor in which a fluorescent derivative is formed by the co-addition of hydrochloric acid and dehydroascorbic acid. Detection of the derivative is accomplished in a fluorometer with excitation at 336 nm and emission at 425 nm. The extraction efficiency for recovery of digoxin from plasma samples was 70% using chloroform-isopropanol (9:1) following a pre-wash with isooctane to remove endogenous substances. The calibration curve was linear (r = 0.9999) over the range 0.5-4 ng/ml digoxin in plasma using digitoxigenin as internal standard. The minimum detectable quantity of digoxin in plasma was 0.5 ng/ml at a signal-to-noise ratio of 4:1. Split-samples of digoxin control sera were assayed by the HPLC procedure and by the prescribed radioimmunoassay procedure. Excellent correlation was observed between the two methods (r = 0.999). No interference was noted when a selection of commonly co-prescribed drugs were evaluated for chromatographic co-elution or interference in detection with that of digoxin or the internal standard.

Digoxin and metabolites in urine and feces: a fluorescence derivatization--high-performance liquid chromatographic technique

A high-performance liquid chromatography method is described for the determination of digoxin and its metabolites digoxigenin, digoxigenin monodigitoxoside, digoxigenin bis-digitoxoside and dihydrodigoxin (20S and 20R) excreted in urine and feces. The urine sample or fecal supernatant is extracted with methylene chloride in the presence of digitoxigenin or digitoxin as internal standard. Pre-column derivatization is achieved using 1-naphthoyl chloride with subsequent separation of the derivatized compounds on either a normal- or reversed-phase system with fluorescence detection. Recoveries for digoxin and all metabolites from fecal samples were in the range 60-74%, which is comparable to that previously determined for urine samples. Standard curve data revealed linearity over a wide range of concentrations. Coefficients of variation for the analysis were less than 10% for all compounds over a range of 5-125 ng per ml urine and 10-250 ng per 200 mg feces. Peaks for digoxin and metabolites in urine and feces were obtained when human excreta were analyzed.

Digoxin and metabolites in urine: a derivatization--high-performance liquid chromatographic method capable of quantitating individual epimers of dihydrodigoxin

A high-performance liquid chromatographic method is described for the determination of digoxigenin, digoxigenin monodigitoxoside, digoxigenin bis-digitoxoside, digoxin, and dihydrodigoxin as the 3,5-dinitrobenzoyl esters. The method is applied to a 10 ml urine sample by adding digitoxigenin as internal standard, extracting with methylene chloride, derivatizing with 3,5-dinitrobenzoyl chloride in pyridine, chromatographing with a normal-phase system and detecting at 254 nm. Derivatized digoxigenin, digoxigenin mono- and bis-digitoxoside, and digoxin each yielded one symmetrical peak with the limit of sensitivity of the method being approximately 100 ng/ml. Analysis of a commercially obtained sample of dihydrodigoxin resulted in two well-separated, symmetrical peaks that represent the two epimers of derivatized dihydrodigoxin. Data indicate rapid and complete esterification of all primary and secondary alcohol moieties in the various molecules and the derivatives are shown to be stable in chloroform for at least four days. The procedure appears to be suitable for metabolic investigations and as a prototype for future analytical developments.

Correlation between the retention of cardiac glycosides in reversed-phase high-performance liquid chromatography with a diphenylsilyl stationary phase, the structure of their molecules and their biological activity

The separation of mixtures of cardiac glycosides by reversed-phase high-performance liquid chromatography on silica gel with chemically grafted diphenylsilyl groups using water-ethanol as the eluent was carried out. It is shown that the configuration and conformation of the glycoside molecules, and the hydrophilic properties of their aglycones and glycones, influence the separation. The hydrophilic properties of the aglycones are more important than those of the glycones. The glycosides with more hydrophilic aglycones have higher biological activity. This is probably related to the easier transport of these glycosides to the receptor.

High-performance liquid chromatography of cardiac glycosides

Highly efficient, short columns have been prepared for the separation of mixtures of cardiac glycosides at relatively small pressure drops. The selectivities of silica adsorbents with different chemically modified surface layers for cardiac glycosides were determined. The influence of the structure of cardiac glycoside molecules on their retention characteristics in liquid chromatography was investigated. The relative number of hydrophobic and hydrophilic groups in the glycoside molecules as well as the configurations are very important for the separation.

High-pressure liquid chromatography of steroids

After a brief discussion of the merits and limitations of high-pressure liquid chromatography (HPLC) relative to other chromatographic methods, special problems in the application to steroids are discussed. Publications on HPLC of steroids are then discussed under the headings of individual classes, arranged generally in the order of increasing polarity.

A comparison of reversed-phase and partition high-performance liquid chromatography of some digitalis glycosides

Comparison of the data for adsorption and reversed-phase chromatography of digitalis glycosides shows the complementary nature of the two modes of separation. The correct choice for a particular problem should make possible a rapid and good separation with simple isocratic systems. Detection limits vary between 10 and 100 ng per injection and permit the analysis of by-products even in low-dosage pharmaceutical formulations. Quantitation is easily possible with both chromatographic techniques using external standardization. The reproducibility for repetitive chromatograms is about 1% relative standard deviation for manual injections by loop injectors and is even significantly better for automatic injection. Reversed-phase chromatography can offer some advantages with regard to sample preparation of pharmaceutical formulations.