Two liquid chromatographic approaches for the simultaneous determination of xipamide and its degradation product (2,6-xylidine) using time-programmed fluorescence detection.

A study of the performance of reversed-phase chromatography with a programmable multiwavelength fluorimetric technique using either conventional hydro-organic or micellar eluent is established for the determination of xipamide (XIP) in the presence of its degradation product, 2,6-xylidine (XY). In conventional liquid chromatography (CLC), the analyses were carried out on a Promosil ODS 100 Å column (250 mm × 4.6 mm i.d., 5 µm) using a mobile phase consisting of methanol/0.1 M phosphate buffer (65: 35, v/v) at pH 4.0. For micellar liquid chromatography (MLC), a short Spherisorb column (150 mm × 4.6 mm i.d., 5 µm) was employed in conjunction with a greener mobile phase (pH 5.0) containing 0.1 M sodium dodecyl sulfate and 15% n-propanol. CLC proved to be superior to MLC in terms of sensitivity for the determination of the degradation product because it could detect trace amounts down to 10.0 ng/ml of XY as a degradation product in XIP. However, MLC represents an eco-friendly approach for the simultaneous determination of XIP and XY. In addition, the opportunity for the direct introduction of biological matrices into the chromatographic system is one of the distinctive benefits of MLC. The proposed methods were applied for the determination of XIP in its tablets, human urine and content uniformity testing. The results of the proposed methods were statistically compared with those obtained using the comparison fluorimetric method, revealing no significant differences in the performance of the methods regarding accuracy and precision.

Stability-Indicating Spectrofluorimetric Methods for the Determination of Metolazone and Xipamide in Their Tablets. Application to Content Uniformity Testing.

A highly sensitive, simple and rapid stability-indicating spectrofluorimetric method was developed for the determination of metolazone (MET) and xipamide (XPM) in their tablets. The proposed method is based on the measurement of the native fluorescence of MET in methanol at 437 nm after excitation at 238 nm and XPM in alkaline methanolic solution at 400 nm after excitation at 255 nm. The fluorescence-concentration plots were rectilinear over the range of 2.0- 20.0 ng/mL for MET and 0.2- 2.0 µg/mL for XPM, with lower detection limits (LOD) of 0.35 ng/mL and 0.02 µg/mL and a lower quantification limit (LOQ) of 1.05 ng/mL and 0.07 µg/mL for MET and XPM, respectively. The method was successfully applied to the analysis of MET and XPM in their commercial tablets and the results were in good agreement with those obtained using the official and comparison methods, respectively. Furthermore, content uniformity testing of the studied pharmaceutical tablets was also conducted. The application of the proposed method was extended to stability studies of MET and XPM after exposure to different forced degradation conditions, such as acidic, alkaline, oxidative and photolytic degradation conditions, according to ICH Guidelines. Moreover, the method was utilized to investigate the kinetics of the alkaline, acidic and photolytic degradation of MET. The apparent first-order rate constants and half-life times were calculated. Proposals for the degradation pathways for both MET and XPM were postulated.

Spectrophotometric and spectrodensitometric determination of triamterene and xipamide in pure form and in pharmaceutical formulation.

Sensitive and validated UV-spectrophotometric, chemometric and TLC-densitometric methods were developed for determination of triamterene (TRM) and xipamide (XIP) in their binary mixture, formulated for use as a diuretic, without previous separation. Method A is the isoabsorptive point spectrophotometry, in which TRM concentration alone can be determined at its λ(max) while XIP concentration can be determined by measuring total concentration of TRM and XIP at their isoabsorptive point followed by subtraction. Method B is the ratio subtraction spectrophotometry, where XIP can be determined by dividing the spectrum of the mixture by the spectrum of TRM (as a divisor) followed by subtracting the constant absorbance value of the plateau region, then finally multiplying the produced spectrum by the spectrum of the divisor, while TRM concentration can be determined at its λ(max). Method C is a chemometric-assisted spectrophotometry where classical least squares, principal component regression, and partial least squares were applied. Method D is a TLC-densitometry; this method depends on quantitative densitometric separation of thin layer chromatogram of TRM and XIP using silica gel plates at 254 nm. The proposed methods were successfully applied for the analysis of TRM and XIP in their pharmaceutical formulation and the results were statistically compared with the established HPLC method.

Experimental design optimization of a capillary zone electrophoresis method for the screening of several diuretics and ACE inhibitors.

Experimental design methodologies are applied to the development of a capillary zone electrophoretic method for the separation of the angiotensin-converting enzyme inhibitor enalapril and its derivative enalaprilat and the diuretics xipamide and hydrochlorothiazide. The effects of pH, buffer concentration, proportion of boric acid in the mixed boric acid-potassium dihydrogen phosphate background electrolyte, temperature, applied voltage, and percentage of organic modifier are studied. Critical factors are identified in a screening design (a 2(6-2) fractional factorial design), and afterwards, optimal conditions for the separation are reached by means of an optimization design (a 2(2) + 2 x 2 + k central composite design). The studied response is the resolution between peaks. The four studied compounds can be separated in less than 3.5 min using an electrolyte of 20mM boric acid-potassium dihydrogen phosphate (75:25, v/v) with 5% MeOH adjusted to pH 8.0 with KOH, at a potential of 30 kV. The detection wavelength and temperature are 206 nm and 35 degrees C, respectively.

[Studies on Xipamide (4-chloro-5-sulfamoyl-2',6'-salicyloxylidide). Part 1: Physico-chemical and chemical properties (author's transl)]. / Untersuchungen mit Xipamid (4-Chlor-5-sulfamoyl-2',6'-salicyloxylidid). Teil I: Physikalisch-chemische und chemische Eigenschaften.

The saluretic agent xipamide (4-chloro-5-sulfamoyl-2',6'-salicyloxylidide; Aquaphor) is a lipophilic substance as demonstrated by solubilities and partition coefficients. In the physiological pH-range, however, xipamide forms an anion which has an octanol-water partition coefficient of approx. 1. Two steps of ionization were investigated photometrically. The first one gives rise to a phenolate anion; pKa1 = 4.75. In the second one, ionization of the sulfamoyl group occurs; pKa2 = 10. Xipamide is stable in acidic as well as in basic media at room temperature. But when xipamide is acted upon by strong alkali and elevated temperature, 2,6-xylidine is formed by hydrolysis. For analytic use UV-photometric, colorimetric and TLC data of xipamide are given.