Resolution of verapamil from heptadeuteroverapamil and their quantitation in serum using capillary gas chromatography

Spectrophotometric method for the determination of verapamil hydrochloride in pharmaceutical formulations using N-bromosuccinimide as oxidant

A rapid, simple and sensitive validated visible spectrophotometric method has been described for the assay of verapamil hydrochloride either in pure form or in pharmaceutical formulations. The method involves the oxidation of the verapamil hydrochloride with N-bromosuccinimide in perchloric acid medium at room temperature, leading to the formation of a yellow colored product, which absorbs maximally at 415 nm. Under the optimized experimental conditions, the color is stable up to 45 min and Beer's law is obeyed in the concentration range of 10.0-200.0 microg ml(-1) with molar absorptivity and Sandell's sensitivity of 2.55 x 10(3) l mol(-1) cm(-1) and 0.192 microg cm(-2) per 0.001 absorbance unit, respectively. The method has been successfully applied to the determination of the drug in commercial dosage forms. Statistical comparison of the results with those of a reference method by means of point and interval hypothesis shows excellent agreement and indicates no significant difference in accuracy and precision. Results of analyses were optimized and validated statistically and through recovery studies. The experimental true bias of all samples is smaller than +/-2%.

Determination of the calcium antagonist SIM6080 in plasma by high-resolution gas chromatography

A sensitive and selective gas chromatographic method for the determination of the calcium antagonist SIM6080 in plasma has been developed and validated. A three-step extraction procedure is employed followed by capillary gas chromatographic analysis using nitrogen-selective detection and the programmed temperature vaporizer injection technique. The defluorinated analogue was used as the internal standard. The analysis of spiked plasma demonstrated the good accuracy and precision of the method with limit of detection of 1 ng/ml. The method has been used for pharmacokinetic studies in laboratory animals.

Chromatography of calcium channel blockers

Numerous publications during the past ten years have described the determination of various calcium channel blockers in biological fluids, using gas and liquid chromatographic techniques. Diltiazem, verapamil, flunarizine and a growing number of dihydropyridines belong to this group of drugs, which in most instances are active at low plasma concentrations. From a bioanalytical point of view these compounds have many features in common, such as high lipophilicity and favourable detection properties.

Effects of the pre-column in automated on-column injection capillary gas chromatography

In this work, we investigated the effects of pre-columns and press-fit connectors on automated cold on-column injection capillary gas chromatography. Verapamil, a calcium channel blocking vasodilator used in the treatment of angina, arrhythmias and hypertension, and norverapamil, an active metabolite, were used as model compounds in these investigations. Wide-bore fused-silica tubing deactivated with OV-1701-vinyl was also studied with respect to its suitability as pre-column material. The detector response of verapamil versus an internal standard was consistent at micrograms/ml and ng/ml levels, while that of norverapamil decreased with the amount injected. However, the decrease in response of norverapamil appeared to be unrelated to the presence of a pre-column or press-fit connector in the chromatographic system.