Rapid quantitative GLC analysis of digoxin

Separation of cardiac glycosides by micellar electrokinetic chromatography and microemulsion electrokinetic chromatography

The interest of micellar electrokinetic chromatography (MEKC) and microemulsion electrokinetic chromatography (MEEKC) for the resolution of four cardiac glycosides is demonstrated. First, the influence of some parameters on the resolution of the solutes in MEKC such as the concentration of the surfactant, pH, addition of organic modifiers and urea is discussed. Then, results are compared with those obtained in MEEKC using different microemulsion compositions. Results indicate that MEEKC possesses several advantages over MEKC for the separation of relatively hydrophobic compounds such as digitalic compounds. First, microemulsions allow a better manipulation of the migration time window and of the retention of the solutes. Moreover, efficiency is improved with shorter analysis time.

High-performance thin-layer chromatographic determination of digoxin and related compounds, digoxigenin bisdigitoxoside and gitoxin, in digoxin drug substance and tablets

A high-performance thin-layer chromatographic (HPTLC) method for the determination of digoxin and its related compounds digoxigenin bisdigitoxoside (DBD) and gitoxin in digoxin drug substance and tablets was developed. Separation of the three compounds was accomplished on a C18 wettable reversed-phase plate using water-methanol-ethyl acetate (50:48:2, v/v/v) as the mobile phase. The analytes were determined by densitometry using absorbance for digoxin and fluorescence for the two related compounds. All peaks were quantified by peak-height analysis. Linear regression analysis of the data was performed for all three compounds. The calibration range for digoxin was set at 320-480 ng per 5-mm band, equivalent to 80-120% (w/w) of a 400-ng band load, that for DBD was set at 4-12 ng per 5-mm band, equivalent to 1-3% (w/w) of the digoxin load, and that for gitoxin was set at 0.4-1.6 ng per 5-mm band, equivalent to 0.1-0.4% (w/w) of the digoxin load. The limit of quantification (LOQ) for digoxin was 64 ng per 5-mm band with a limit of detection (LOD) of 8 ng per 5-mm band. The LOQs for both DBD and gitoxin were 0.12 ng per 5-mm band with LODs of 0.4 ng per 5-mm band. The linearity range for the digoxin peak height in the absorbance mode was 0-5000 ng per 5-mm band. The linearity range for DBD and gitoxin peak heights in the fluorescence mode was 0-2000 ng per 5-mm band.

Micro high-performance liquid chromatographic determination of cardiac glycosides in beta-methyldigoxin and digoxin tablets

A micro high-performance liquid chromatographic (micro-HPLC) method has been developed for the assay of beta-methyldigoxin and digoxin tablets. Quantitation of cardiac glycosides in tablets was carried out by the incorporation of dexamethasone as an internal standard. The procedure consisted of disintegration of tablets, extraction with acetone-ethanol (9:1) and injection for micro-HPLC on an ODS micro column, using acetonitrile-water (28:72) for beta-methyldigoxin tablets and methanol-water (1:1) for digoxin tablets; the effluent was monitored by UV detection at 220 nm. The average values of the contents in beta-methyldigoxin and digoxin tablets were 99.6 and 100.2% of the labelled amounts, respectively. The proposed method is sufficiently precise and sensitive to examine the content uniformity of tablets.

Comparison of high-performance liquid chromatography and radioimmunoassay in the determination of content uniformity of digoxin tablets

Digoxin 0.25-mg tablets were dissolved and assayed by the standard high-performance liquid chromatography (HPLC) method specified in USP XX and by a radioimmunoassay (RIA) method modified for the assay of tablet solutions. For the RIA method, the filtrate was diluted to a theoretical concentration of 5 ng/ml. Aliquots of this dilution were then assayed for digoxin content using a commercial digoxin 125I RIA kit. Results from both methods were extrapolated to total tablet content and compared with the labeled amount for 20 individual tablets. All tablet assay results were within the USP standards for content uniformity of individual tablets. The individual tablet deviations from labeled amount by the RIA method were smaller when compared with the USP XX-specified HPLC method. Comparison of individual tablet assays show the RIA method to be both as precise and as accurate as the USP XX-specified HPLC method.

High-performance liquid chromatographic analysis of digoxin formulations

A rapid, selective, and simple high-performance liquid chromatographic (HPLC) assay for digoxin formulations is described. The method utilizes a conventional octadecyl bonded phase column with detection at 220 nm. The analytical procedure has been applied for the quantitation of digoxin in tablets, elixir, and injectable formulations with a resulting relative standard deviation of 1.45, 1.70, and 1.80%, respectively. The method is sufficiently sensitive to monitor content uniformity of individual tablets. Potential impurities or degradation products are resolved from the digoxin peak in a total chromatographic time of less than 15 min.