Gamal H. Ragab

Colorimetric determination of β-blockers in pharmaceutical formulations

Abstract A simple, accurate, precise and sensitive colorimetric method for the determination of some β-blockers as atenolol (Ateno), metoprolol (Metop), sotalol (Sot) and nadolol (Nad) is described. This method is based on the formation of charge transfer complex with 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD–Cl) in methanolic–aqueous (for Ateno and Metop) or acetone–aqueous (for Sot and Nad) medium [30% (v/v)]. The orange color products are measured at 485, 470, 465 and 462 nm for Ateno, Metop, Sot and Nad, respectively. The optimization of various experimental conditions is described. Beers law is obeyed in the range 0.4–60 μg ml−1 while that obtained applying Ringbom is 0.8–56 μg ml−1. The molar absorptivity, Sandell sensitivity, detection and quantification limits are calculated. The results obtained showed good recoveries of 99.5±1.1, 100.3±1.2, 100.5±1.0 and 99.3±1.1% with relative standard deviations of 0.74, 0.98, 1.15 and 0.87% for Ateno, Metop, Sot and Nad, respectively. Applications of the proposed method to representative pharmaceutical formulations are successfully presented.

Atomic absorption spectroscopic, conductometric and colorimetric methods for determination of fluoroquinolone antibiotics using ammonium reineckate ion-pair complex formation.

Three accurate, rapid and simple atomic absorption spectrometric, conductometric and colorimetric methods were developed for the determination of norfloxacin (NRF), ciprofloxacin (CIP), ofloxacin (OFL) and enrofloxacin (ENF). The proposed methods depend upon the reaction of ammonium reineckate with the studied drugs to form stable precipitate of ion-pair complexes, which was dissolved in acetone. The pink coloured complexes were determined either by AAS or colorimetrically at lambdmax 525 nm directly using the dissolved complex. Using conductometric titration, the studied drugs could be evaluated in 50% (v/v) acetone in the range 5.0-65, 4.0-48, 5.0-56 and 6.0-72 microg ml-1 of NRF, CPF, OFL and ENF, respectively. The optimizations of various experimental conditions were described. The results obtained showed good recoveries of 99.15 +/- 1.15, 99.30 +/- 1.40, 99.60 +/- 1.50, and 99.00 +/- 1.25% with relative standard deviations of 0.81, 1.06, 0.97, and 0.69% for NRF, CPF, OFL, and ENF, respectively. Applications of the proposed methods to representative pharmaceutical formulations are successfully presented.

HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC AND SPECTROPHOTOMETRIC DETERMINATIONS OF PIOGLITAZONE-HCl EITHER ALONE OR IN COMBINATION WITH METFORMIN-HCl

HPLC and spectrophotometric methods are described for pioglitazone-HCl determination in bulk powder and the dosage forms either alone or combined with metformin-HCl. The chromatographic method involves separation of pioglitazone-HCl and metformin-HCl on a monolithic column, using mobile phase of MeOH and 25 mM KH2PO4 at pH 4.9 in ratio of 75:25 (v/v) at flow rate of 2.7 mLmin−1, at 25°C, and at 210 nm. Total elution time is less than one minute. The method is validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, and robustness. Robustness is studied for small changes in pH, flow rate, % of MeOH, and injection volume. Limits of detection are 0.5 and 0.25 µgmL−1 for them, respectively. Recovery values of this method are between 97% and 103% and reproducibility values are within 0.99 for pioglitazone-HCl and 1.5 for metformin-HCl. Spectrophotometric method is based on oxidation of pioglitazone-HCl with excess n-bromosuccinimide followed by oxidation of metol through unreacted amount of n-bromosuccinimide and then coupling between oxidation product of metol and sulphanilic acid. Metformin-HCl does not interfere with this method. The colored compound developed in acidic medium was measured at 520 nm. Beers law is obeyed in the concentration range of 5–20 µgmL−1.

Simple Atomic Absorption Spectroscopic and Spectrophotometric Methods for Determination of Pioglitazone Hydrochloride and Carvedilol in Pharmaceutical Dosage Forms

This study represents simple atomic absorption spectroscopic and spectrophotometric methods for determination of pioglitazone hydrochloride (PGZ-HCl) and carvedilol (CRV) based on formation of ion-pair associates between drugs and inorganic complex, bismuth(III) tetraiodide (Method A) and between drugs and organic acidic dyes, fast green and orange G (Method B). Method A is based on formation of ion-pair associate between drugs and bismuth(III) tetraiodide in acidic medium to form orange-red ion-pair associates, which can be quantitatively determined by two different procedures. The formed ion-pair associate is extracted by methylene chloride, dissolved in acetone, dried, and then decomposed by hydrochloric acid, and bismuth content is determined by direct atomic absorption spectrometric technique (Procedure 1) or extracted by methylene chloride, dissolved in acetone, and quantified spectrophotometrically at 490 nm (Procedure 2). Method B is based on formation of ion-pair associate between drugs and either fast green dye or orange G dye in acidic medium to form ion-pair associates. The formed ion-pair associate is extracted by methylene chloride and quantified spectrophotometrically at 630 nm (for fast green dye method) or 498 nm (for orange G dye method). Optimal experimental conditions have been studied. Both methods are applied for determination of the drugs in tablets without interference.

Sensitive Spectrophotometric and Conductometric Methods for the Determination of Candesartan Using Acidic Dyes

Two simple, sensitive, accurate, rapid spectrophotometric and conductometric methods were developed for the determination of candesartan (CAND) in raw material and in its pharmaceutical preparation. The proposed methods depend upon the reaction of bromocresol green (BCG) or bromocresol purple (BCP) with candesartan in phosphate buffered solution to form stable colored ion-pair complex, which was extracted in chloroform. The yellow colored complexes were determined at λmax 415, 405 nm with BCG, BCP, respectively. Using conductometric titration, candesartan could be evaluated in acetone. The optimizations of various experimental conditions were described. The results obtained showed good recover of 100.14 (n=6) with relative standard deviation of 0.62 (n=6). Applications of the proposed methods to representative pharmaceutical formulations are successfully presented compared with official methods.

Validated, Ultra High Efficiency RP-HPLC and Stability Indicating Method for Determination of Tranylcypromines Sulphate in Bulk and in Tablet Dosage Forms

at 30 ° C, using simple isocratic mobile phase of acetonitrile - orthophosphoric acid 0.1 % (10: 90, v/v). The flow rate was 1.0 mL/min and the detection was performed at 220 nm. The retention time of the drug was 2 min while for the reported method was 6.7 min. The method was validated according to International Conference on Harmonization (ICH) guidelines. Tranylcypromine was subjected to the stress conditions of hydrolytic acidic, basic, oxidative, and photolytic degradation. The assay was linear over the concentration range of 3-150 µg mL -1 and the correlation coefficient was 1. The RSD% of inter and intraday precision was less than 1 %. The % recoveries were found to be 100.58 % proved that the proposed method is sufficiently accurate and precise. The method distinctly separates the drug from its degradation products within 2 min and total run time of 8 min.

Application of non-steroidal anti-inflammatory drugs for palladium determination

A highly sensitive spectrophotometric method for palladium determination using piroxicam and tenoxicam as new chromogenic reagents has been developed. In the presence of sodium lauryl sulfate (SLS), palladium reacts with piroxicam (PX) or tenoxicam (TX) to form stable yellow orange complexes in an acetate buffer solution of pH 5.0 at 424 nm and 426 nm with molar absorptivity of 7.16 × 104 L mol−1 cm−1 and 1.20 × 105 L mol−1 cm−1, respectively. Sandell sensitivity, detection, and quantitation limits were also calculated. Optimum conditions were evaluated considering pH, reagent concentration, time, temperature, and surfactant concentration. The complex system conforms to Beer’s law over the range of 0.07–1.28 μg mL−1 palladium. The stoichiometric ratio and stability constant were also evaluated. Tolerance limits of many cations and anions were determined. Finally, the proposed method was applied successfully in the determination of palladium in jewellery, anode mud, synthetic mixtures, catalysts, and alloy samples.