Statistical optimization of a reversed-phase liquid chromatographic method for the analysis of amiloride and hydrochlorothiazide in tablets.

A method has been developed for the separation of hydrochlorothiazide and amiloride by high-performance liquid chromatographic (HPLC) method on a C18 column with detection at 280 nm. The optimal conditions of separation were determined with the aid of 'window diagram' technique of Laub and Purnell. The effect of simultaneously varying the pH, proportion aqueous acetic acid and methanol in the mobile phase were studied to optimize the separation. A response surface diagram was used to optimize the experimental conditions for the separation. The mobile phase composition that provides an acceptable resolution hydrochlorothiazide and amiloride in a short elution time is water:methanol (60:40) and pH 3.2 (pH adjusted to 3.2 with CH3COOH). A method is applied for the quantitative analysis of Moduretic tablets (Merck Sharp & Dokme International). The powdered tablets are extracted with methanol, containing caffeine as the internal standard, and assayed by comparison of peak areas after liquid chromatography.

Statistical optimization of a reversed-phase liquid chromatographic method for the determination of amiloride and methyclothiazide in tablets.

A quantitative high-performance liquid chromatographic method in which amiloride is separated from methyclothiazide on a C18 column with detection at 286 mm was developed with the aid of the 'window diagram' technique of Laub and Purnell. The effect of simultaneously varying the pH and methanol to water ratio in the mobile phase were studied to optimize the separation. The method was applied to the quantitative analysis of Lometazid tablets. The powdered tablets were extracted with methanol, containing phenacetin as the internal standard, and assayed by comparison of peak heights after liquid chromatography.

High-performance liquid chromatographic determination of tilidine in pharmaceutical dosage forms.

A reversed-phase high performance liquid chromatographic method for the determination of tilidine in bulk drug and its liquid and solid dosage forms is described. The method uses reversed-phase column RP-8 with methanol -0.2% water solution of ammonium carbonate (75:25,v/v) as the mobile phase and UV detector. The time taken for separation is 6.17 min. The response is linear up to 3.6 mmol/l, with recovery levels ranging from 98.2 to 101.2%. The present method is rapid, simple and reproducible.

Spectrophotometric study of polythiazide-palladium (II) complex.

A quantitative spectrophotometric method using Pd(II) chloride as analytical reagent for the determination of polythiazide in pharmaceutical preparations is described in this study. It has been found that polythiazide reacts with Pd(II) chloride in the pH range 3.6-5.8, forming a red, water-soluble (1:1) complex with maximum absorbance at 527 nm. At the optimum pH of 4.8 and an ionic strength mu = 0.1 M, the conditional stability constant of the complex is found to be log K' = 4.77. The molar absorptivity at 527 nm is 3.2 x 10(3) l mol-1 cm-1. Good agreement with Beer's law was found for polythiazide concentrations up to 2.2 mmol l-1. The nominal percent recovery of polythiazide was 99.5% (n = 20). The simplicity, selectivity and sensitivity of the method described is suitable for rapid and accurate determinations of polythiazide in tablets.