Hisham Hashem

Effect of chromatographic conditions on liquid chromatographic chiral separation of terbutaline and salbutamol on Chirobiotic V column

In this study, a method for enantioseparation of terbutaline and salbutamol was established using Chirobiotic V column as a stationary phase. Polar ionic mode applying mobile phase containing ammonium nitrate in 100% ethanol, pH 5.1 was found to give the best separation. The salt concentration in the mobile phase and pH value were found to be the most important chromatographic factors affecting separation. Separation of enantiomers of these two basic analytes was complete in less than 10 min without applying ammonium trifluoroacetate (ATFA) or triethylamine (TEA) salts.

Spectophotometric methods for determination of cefdinir in pharmaceutical formulations via derivatization with 1,2-naphthoquinone-4-sulfonate and 4-chloro-7-nitrobenzo-2-oxa-1, 3-diazole

Two new simple, sensitive, accurate, and precise spectrophotometric methods have been developed and validated for the determination of cefdinir (CFD) in bulk drug and in its pharmaceutical formulations. The first method was based on the reaction of CFD with 1, 2- napthaquinone-4- sulfonic acid sodium (NQS) in an alkaline medium (pH 11) to form an orange-coloured product that was measured at 490 nm. The second method depends on hydrolysis of CFD using 0.5 M NaOH at 100 °C and subsequent reaction of the formed sulfide ions with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) to form a yellow-coloured chromogen measured at 390 nm. Different variables affecting the reactions of CFD with both NQS and NBD-Cl (e.g. NaOH concentration, hydrolysis time, NQS or NBD-Cl concentration and diluting solvent) were studied and optimized. Under optimum conditions, good linear relationships with good correlation coefficients (0.9990-0.9999) were found in the range of 10-80 and 5.0-30 µg ml(-1) for NQS and NBD-Cl, respectively. The limits of assay detection and quantitation ranged from 1.097 and 0.280 and 3.656 and 0.934 µg ml(-1) for NQS and NBD-Cl, respectively. The accuracy and precision of the proposed methods were satisfactory. The proposed method is simple, rapid, precise and convenient and was successfully applied for analysis of CFD in its pharmaceutical formulations and the recovery percentages ranged from 99.25 to 100.20%.

COMPARISON BETWEEN CALIXARENE AND CONVENTIONAL HPLC-STATIONARY PHASES CONCERNING WITH SEPARATION OF ANTIHYPERTENSIVE DRUGS

In this article, the effect of changes in different process variables such as pH, buffer type and concentration, column temperature, injection volume, as well as type and contents of organic modifier on retention behavior of seven antihypertensive drugs from two different categories (Angiotensin II receptor blockers and Diuretics) was investigated. Conventional RP-C18 column (Intersil® ODS-3) and calixarene column (Caltrex BIII®) were used as stationary phases. Calixarene-based stationary phases differ from the conventional RP-C18 in that they are as cyclodextrins in having cavities. The results showed that the examined conditions had different effects on the analytes retention on both columns, for example the elution order had changed and resolution between different analytes took variable behaviors. This can be attributed to the different chemical structures of both stationary phases used. The obtained results indicate that the used stationary phases behave as reversed phases packing and the hydrophobic interaction is main factor having a role in the retention of antihypertensive drugs. The chemical structure and properties of the analytes were found to have an effective role in their separation.

DEVELOPMENT AND VALIDATION OF A RAPID STABILITY INDICATING CHROMATOGRAPHIC DETERMINATION OF CEFDINIR IN BULK POWDER AND DOSAGE FORM USING MONOLITHIC STATIONARY PHASE

A simple, rapid, and accurate, routine-HPLC method is described for quantitation of Cefdinir in bulk powder and dosage form. The chromatographic separation was carried out on Chromolith Performance RP-18e column, a relatively new packing material consisting of monolithic rods of highly porous silica, using isocratic binary mobile phase of MeOH and 25 mM KH2PO4 pH 3.0 in the ratio of 10:90 at flow rate of 5 mL/min and 40°C. A diode array detector was used at 214 nm for detection. The elution time of Cefdinir was found to be 2.183 ± 0.003 minutes. The method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability, and robustness. The robustness study was done for small changes in KH2PO4 concentration and pH, temperature, flow rate, wavelength of detection, % of MeOH in mobile phase, and injection volume. Stability tests were done through exposure of the analyte solution for four different stress conditions: Reflux with 1 N HCl, reflux with 1 N NaOH, reflux with 30% H2O2 and exposure to UV radiation. The limits of detection and quantification were 0.313 and 0.625 µgmL−1, respectively. The recovery value of this method was 98.00% and the reproducibility was within 2.98.

Comparison of the chromatographic behavior of tricyclic neuroleptics on calixarene-bonded, monolithic and conventional RP-HPLC columns.

The effect of different chromatographic conditions, such as buffer concentration and type of organic modifier, on the retention behavior of nine tricyclic neuroleptics on three different RP-HPLC columns was investigated. Two recently developed columns, calixarene-bonded (CALTREX) AIII) and monolithic (Chromolith) Performance RP-18e) columns, were compared with a conventional RP-C18 HPLC column (LiChrospher). The results showed how the mobile phase conditions had different effects on the analyte retention on these three columns. For example, the elution order of some analytes and the initiation of separation of the geometric isomers of the three analytes--which have E/Z-isomers (cis/trans-isomers)--could be altered by changing the conditions and the column type. Under identical conditions, a calixarene-bonded phase was the best for this separation, a monolithic phase gave comparable results and the conventional RP-column was the least effective. Concerning the geometric isomers separation, the Chromolith Performance RP-18e was superior.

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.

SIMULTANEOUS HPLC-DETERMINATION OF NORTRIPTYLINE AND FLUPHENAZINE IN ONE MINUTE USING MONOLITHIC STATIONARY PHASE

A simple, fast, robust, and accurate high-performance liquid chromatography (HPLC) method is described for simultaneous quantification of nortriptyline and fluphenazine in bulk powder and dosage forms. The chromatographic separation was carried out in less than one minute on Chromolith® Performance RP-18e column, which consists of monolithic rods of highly porous silica, using isocratic binary mobile phase of MeOH and 25 mM KH2PO4 pH 4.5 in the ratio of 70: 30 at 5 mL min−1 flow rate and 40°C. The high porosity of stationary phase enables it to be used at high flow rates without problems concerning backpressure, these high flow rates in turn lead to strong reduction of analysis time. A diode array detector was used at 254 nm for detection. The method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, and robustness. LOD were found to be 0.40 and 0.78 µg mL−1 for nortriptyline and fluphenazine, respectively. LOQ was 3.125 µg mL−1 for both analytes. Recovery values of this method were 98.50 and 98.00% for nortriptyline and fluphenazine, respectively, and reproducibility was within 2.36%. Robustness study was done for small changes in KH2PO4 concentration and pH, temperature, flow rate, wavelength of detection, % of MeOH in mobile phase, and injection volume.

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.

Development and validation of a rapid stability indicating HPLC-method using monolithic stationary phase and two spectrophotometric methods for determination of antihistaminic acrivastine in capsules

Simple, rapid and accurate high performance liquid chromatographic (HPLC) and spectrophotometric methods are described for determination of antihistaminic acrivastine in capsules. The first method (method A) is based on accurate, sensitive and stability indicating chromatographic separation method. Chromolith® Performance RP-18e column, a relatively new packing material consisting of monolithic rods of highly porous silica, was used as stationary phase applying isocratic binary mobile phase of ACN and 25 mM NaH2PO4 pH 4.0 in the ratio of 22.5:77.5 at flow rate of 5.0 mL/min and 40°C. A diode array detector was used at 254 nm for detection. The elution time of acrivastine was found to be 2.080±0.032. The second and third methods (methods B and C) are based on the oxidation of acrivastine with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilic acid (λmax: 520 nm) or amaranth dye (λmax: 530 nm). The reacted oxidant corresponds to the drug content. Beers law is obeyed over the concentration range 1.563-50, 2.0-20 and 1.0-10 μg mL(-1) for methods A, B and C, respectively. The limits of detection and quantitation were 0.40, 0.292 and 0.113 μg mL(-1) and 0.782, 0.973 and 0.376 μg mL(-1) for methods A, B and C, respectively. The HPLC method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability and robustness. Stability tests were done through exposure of the analyte solution for four different stress conditions and the results indicate no interference of degradants with HPLC-method. The proposed methods was favorably applied for determination of acrivastine in capsules formulation. Statistical comparison of the obtained results from the analysis of the studied drug to those of the reported method using t- and F-tests showed no significant difference between them.

DEVELOPMENT AND VALIDATION OF RAPID STABILITY INDICATING HPLC-DETERMINATIONS OF ANTIEPILEPTIC DRUGS PHENOBARBITAL IN SUPPOSITORIES AND PHENYTOIN IN CAPSULES AS WELL AS IN URINE SAMPLE

Two simple, rapid, accurate, and stability indicating HPLC methods are described for quantitation of Phenobarbital and Phenytoin in bulk powders, dosage forms, or urine. Chromatographic quantitation of Phenobarbital was developed on Chromolith® Performance RP-18e column, using isocratic binary mobile phase of MeOH and H2O (38: 62, V/V) at flow rate of 3 mLmin−1. Determination of Phenytoin was achieved using a conventional RP C-18, applying isocratic binary mobile phase of ACN and H2O (25: 75, V/V) at flow rate of 1 mL min−1. The elution times of Phenobarbital and Phenytoin are 1.397 ± 0.039 and 5.604 ± 0.013 min, respectively. Each method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability, and robustness. Stability tests were done through exposure of the analyte solutions to four different stress conditions: reflux with 1 N HCl, reflux with 1 N NaOH, reflux with 30% H2O2, and exposure to UV radiation. Limits of detection and quantitation were 0.125 and 0.250 µgmL−1 as well as 0.250 and 0.500 µgmL−1 for Phenobarbital and Phenytoin, respectively. Due to the short separation time of Phenobarbital, the method was applied for dissolution study in presence of beta-cyclodextrin. The proposed methods can be used for routine samples or stability studies.