Abdalla A. Elbashir

Determination of aminoglutethimide enantiomers in pharmaceutical formulations by capillary electrophoresis using methylated-β-cyclodextrin as a chiral selector and computational calculation for their respective inclusion complexes

A capillary electrophoretic method for the separation of the aminoglutethimide (AGT) enantiomers using methylated-beta-cyclodextrin (M-beta-CD) as chiral selector is described. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 9 min with resolution factor Rs=2.1, using a fused-silica capillary and a background electrolyte (BGE) of tris-phosphate buffer solution (50 mmol L(-1), pH 3.0) containing 30 mgm L(-1) of M-beta-CD. The separation was carried out in normal polarity mode at 25 degrees C, 16 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy/recovery were included. The proposed method was successfully applied to the assay of AGT enantiomers in pharmaceutical formulations. The computational calculations for the inclusion complexes of the R- and S-AGT-M-beta-CD rationalized the reasons for the different migration times between the AGT enantiomers.

Validated Stability Indicating Assay of Gemifloxacin and Lomefloxacin in Tablet Formulations by Capillary Electrophoresis

Abstract A capillary zone electrophoretic (CZE) method has been developed for the determination of gemifloxacin and lomefloxacin in pharmaceutical tablet formulations. The CZE separation was performed using a 75 µm×35 cm fused silica capillary under the following conditions: 25°C; applied voltage, 12 kV; 25 mM H3PO4‐NaOH running buffer (pH 8.5). The detection wavelength was 254 nm. Flumequine was used as internal standard. The method was suitably validated with respect to linearity, limit of detection and quantification, accuracy, precision, specificity, and robustness. The calibration was linear from 5 to 50 µg mL−1 for gemifloxacin and 10 to 60 µg mL−1 for lomefloxacin, and the limit of detection and quantification were 2.93, 4.91 µg mL−1, and 3.87, 8.93 for gemifloxacin and lomefloxacin, respectively. Recoveries ranging from 94.4–108.6% were obtained for both drugs. The method was successfully applied to the determination of gemifloxacin and lomefloxacin in pharmaceutical tablets. Excipients present in the tablets and degraded products from different stress conditions did not interfere in the assay.

Capillary electrophoretic separation and computational modeling of inclusion complexes of β-cyclodextrin and 18-crown-6 ether with primaquine and quinocide

The antimalarial drug primaquine (PQ) and its contaminant, the positional isomer quinocide (QC) have been successfully separated using capillary electrophoresis with either beta-cyclodextrin (beta-CD) or 18-crown-6 ether (18C6) as chiral mobile phase additive. The interactions of the drugs with cyclodextrins and 18C6 were studied by the semiempirical method (Parametric Model 3) PM3. Theoretical calculations for the inclusion complexes of PQ and QC with alpha-CD, beta-CD and 18C6 were performed. Data from the theoretical calculations are correlated and discussed with respect to the electrophoretic migration behavior. More stable complexes are predicted for the PQ-beta-CD and PQ-18C6 complexes. The coelution of PQ and QC when alpha-CD was used as buffer additive can be explained by their comparable stabilities of the inclusion complex formed, while significant differences in the complexation stabilities of the drugs with beta-CD is responsible for their separation. The stronger hydrogen bonding in PQ-18C6 system is responsible for the separation between PQ and QC when 18C6 was used as chiral mobile phase additive.

Determination of Ofloxacin Enantiomers in Pharmaceutical Formulations by Capillary Electrophoresis

Abstract A capillary electrophoretic method for the separation of the enantiomers of ofloxacin using carboxymethyl‐β‐cyclodextrin (CM‐β‐CD) as chiral selector is described. The effect of the type of cyclodextrin and its concentration, buffer concentration, and its pH, as well as instrumental parameters, such as applied voltage and temperature were systematically studied. The highest resolution of ofloxacin enantiomers obtained was around 2.8. This was achieved using Tris‐citrate buffer (pH 4.5) that contained 3 mg mL−1 CM‐β‐CD and using UV detection (254 nm), applied voltage (12 kV), and capillary temperature of 25°C. Acceptable validation criteria for selectivity, precision, linearity, limit of detection, and quantitation were also included. Recoveries between 98.3–103.4% were obtained when the method was used to determine the enantiomers of ofloxacin that were spiked to placebos. The proposed method is fast, sensitive, inexpensive, and its usefulness was demonstrated for the analysis of five pharmaceutical preparations, two of which just contained the S‐ofloxacin while the other three contained both isomers as racemic mixtures.

Determination of quinocide as impurity in primaquine tablets by capillary zone electrophoresis.

A capillary zone electrophoretic method has been developed and validated for the determination of the impurity quinocide (QC) in the antimalarial drug primaquine (PQ). Different buffer additives such as native cyclodextrins and crown ethers were evaluated. Promising results were obtained when either beta-cyclodextrin (beta-CD) or 18-crown-6 ether (18C6) were used. Their separation conditions such as type of buffer and its pH, buffer additive concentration, applied voltage capillary temperature and injection time were optimized. The use of 18C6 offers slight advantages over beta-CD such as faster elution times and improved resolution. Nevertheless, migration times of less than 5 min and resolution factors (R(s)) in the range of 2-4 were obtained when both additives were used. The method was validated with respect to selectivity, linearity, limits of detection and quantitation, analytical precision (intra- and inter-day variability) and repeatability. Concentrations of 2.12 and 2.71% (w/w) of QC were found in pharmaceutical preparations of PQ from two different manufacturers. A possible mechanism for the successful separation of the isomers is also discussed.

Recent Developments of Enantioseparations for Fluoroquinolones Drugs Using Liquid Chromatography and Capillary Electrophoresis

Fluoroquinolones antibiotics are more effective pathogens resistant to other antibacterial, thus being regularly prescribed drugs in human and veterinary medicine. Many fluoroquinolones posses one or two stereogenic centers giving rise to enantiomers whose pharmacological properties and toxicity are often different. At the successive stages of drug discovery, the enantiomers of any chiral molecule must be isolated and analyzed and their enantiomeric purity determined. The present review summarizes recent developments on chiral separation of fluoroquinolones using chromatographic and electrophoretic techniques.

Simultaneous Determination of Atenolol and Chlorthalidone in Pharmaceutical Preparations by Capillary-Zone Electrophoresis

Abstract A capillary zone electrophoresis (CZE) method for the simultaneous determination of the β-blocker drugs atenolol and chlorthalidone in pharmaceutical formulations has been developed. The CZE separation was performed under the following conditions: capillary temperature, 25°C; applied voltage, 25 kV; 20 mM H3PO4–NaOH running buffer (pH 9.0); and detection wavelength, 198 nm. Phenobarbital was used as internal standard. The method was validated and showed not only good precision and accuracy but also good robustness. The method has been successfully applied to the simultaneous determination of both atenolol and chlorthalidone in pharmaceutical tablets.

Enantioselective analysis of primaquine and its impurity quinocide by capillary electrophoresis.

A capillary electrophoretic (CE) method for the baseline separation of the enantiomers of primaquine diphosphate (PQ) and quinocide (QC) (a major contaminant) in pharmaceutical formulations is proposed. Both components were separated under the following conditions: 50 mm tris phosphate buffer (pH 3.0) containing 15 mm hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as background electrolyte; applied voltage, 16 kV; capillary temperature, 25 degrees C; detection wavelength, 254 nm; hydrostatic injection, 10 s. The separations were conducted using a 35 cm length and 50 microm i.d. uncoated fused silica capillary column. Under the optimized conditions, the components were successfully separated in about 5 min. Intraday precision of migration time and corrected peak areas when expressed as relative standard deviation ranged from 0.17 to 0.45 and 2.60 to 3.94%, respectively, while the interday precision ranged from 2.59 to 4.20 and 3.15 to 4.21%, respectively. After the validation exercise, the proposed method was applied for the determination of QC impurity in PQ formulations.

Development and Validation of a Capillary Zone Electrophoresis Method for the Determination of Ofloxacin in Tablets

Abstract A capillary zone electrophoresis (CZE) method has been developed for the determination of the antibiotic ofloxacin in tablets. The CZE separation was performed using 75 µm × 35 cm fused silica capillary under the following conditions: 25°C; applied voltage, 12 kV; 25 mM H3PO4-NaOH running buffer (pH 8.5). The detection wavelength was 254 nm. Flumequine was used as internal standard. The method was suitably validated with respect to linearity, limit of detection and quantification, accuracy, precision, specificity, and robustness. The calibration was linear from 5 to 50 µg mL−1 and the limit of detection and quantification were 1.24 and 4.01 µg mL−1, respectively. Recoveries ranging from 99.71–102.4% were obtained in the determination of ofloxacin that were spiked to placebos. Excipients in the commercial tablets and degraded products from different stress conditions did not interfere in the assay. The method was successfully applied to the determination of ofloxacin in pharmaceutical tablets.

Development and Validation of Spectrophotometric Methods for the Determination of Mesalazine in Pharmaceutical Formulation

Two simple, accurate and precise spectrophotometric methods for the quantitative analysis of mesalazine (MSZ) in pharmaceutical formulation have been described. The first method (A) is based on the charge transfer reaction with alizarin red sulphonate (ARS) in the solution of pH 8.0 to form a violet product showing maximum absorbance at 600 nm. The second method (B) is a derivatisation method involving reaction of MSZ with 1,2-naphthoquinone-4- sulphonate (NQS) in alkaline medium at pH 12.0 to form an orange product exhibiting maximum absorbance at 470 nm. All variables affecting the reactions were studied and optimized. Beers law was obeyed in the concentration ranges of 15-97.5 and 2-22 μg/mL for methods A and B, respectively. The molar absorptivity, Sandell sensitivity, detection and quantification limits were calculated. The two methods were successfully applied to the determination of MSZ in pharmaceutical formulation.