Ahmed O. Alnajjar

Capillary electrophoresis for the determination of norfloxacin and tinidazole in pharmaceuticals with multi-response optimization

Capillary electrophoresis (CE) with UV photo-diode array detection technique was utilized to adopt new method for the analysis of norfloxacin and tinidazole in pharmaceuticals. Many CE aspects including separation, rapidity, sensitivity, ruggedness as well as the repeatability of qualitative and quantitative analyses were considered simultaneously for the purpose of optimization. Experimental design approach including factorial design and response surface methods were applied to optimize electrolyte concentration and the pH while injection time, voltage and column temperature were optimized using the univariate method. Successful results were obtained using 32.5mmoll(-l) phosphate electrolyte at pH 2.5, injection time 8.0s, voltage 25kV and column temperature 25 degrees C with detection at wavelength 301nm. The analytical characteristics including recovery, intermediate precision, linear dynamic ranges, linearity and selectivity as well as limits of detection and quantification were demonstrated and the applicability to pharmaceuticals was studied. The newly provided method enjoys the advantages of CE over HPLC with respect to rapidity, ruggedness, simplicity in reagents and sample preparation as well as saving in reagents and samples.

Capillary Electrophoresis Assay Method for Metoprolol and Hydrochlorothiazide in their Combined Dosage Form with Multivariate Optimization

The current manuscript reports the first capillary electrophoresis method for the separation and quantification of metoprolol (MET) and hydrochlorothiazide (HCT) in their combined dosage form. MET and HCT were detected at 240 and 214 nm, respectively, using a photodiode array detector. The univariate approach was used for optimizing voltage, injection time and capillary temperature. The factorial design with response surface plots, as a multivariate approach, was used to study the effect of buffer concentration and pH on resolution, peak area and migration time. The optimum conditions were 50 mmol/L phosphate at pH 9.5, injection time 10.0 s, voltage 25 kV and capillary temperature 25°C. The method was linear in the range of 2.5-250 µg/mL for both drugs with correlation coefficients above 0.9997. Additionally, acceptable recovery of the contents of MET and HCT in their formulations (96.0-100.3%) with acceptable precision (1.38-2.60 %) were achieved. Moreover, the limits of detection of MET and HCT were 0.02 and 0.01 µg/mL, respectively, which were suitable for pharmaceutical analysis.

SIMULTANEOUS DETERMINATION OF OFLOXACIN AND CEFIXIME IN TABLET FORMULATION USING CAPILLARY ELECTROPHORESIS

In the current study, the first capillary electrophoresis (CE) method for the simultaneous determination of ofloxacin (OFL) and cefixime (CEF) in their combined and single dosage forms was reported. Successful separation was achieved using 31.2 cm long × 50 µm I.D. fused-silica capillary, 10 mM phosphate electrolyte at pH 10, injection time 10.0 s, voltage 25 kV and column temperature 25°C. A photo diode array detector was used at wavelength 254 nm. The method was validated and accuracy, precision, linearity, and limits of detection and quantitation were examined. An excellent linearity was obtained at a wide concentration range (5–200 µg/mL). The method is also sensitive enough for pharmaceutical analysis. The limit of detection for OFL and CEF was 0.12 µg/mL and 0.21 µg/mL, respectively. For method application, acceptable recovery (100.2–105.3%) was obtained for all examined samples. The method has the advantages of CE over HPLC with respect to rapidity, simplicity in reagents, and sample preparation as well as saving in reagents.

A conventional HPLC-MS method for the simultaneous determination of ofloxacin and cefixime in plasma: Development and validation.

Objective: A simple, rapid, and sensitive high performance liquid chromatography-mass spectrometry (HPLC-MS) method was developed and validated for the simultaneous determination of ofloxacin (OFL) and cefixime (CEF) in human plasma using the moxifloxacin as internal standard. Methodology: Analytes were separated using an Agilent LCMS system equipped with a Zorbax eclipse XBD C18 column (150 mm × 4.6 mm i.d., 5 μm) and using a mobile phase consisting of a mixture of acetonitrile, methanol and 0.5% formic acid in a ratio of 23:10:67% v/v and flow rate was set at 0.6 mL/min. Plasma samples were extracted using the protein precipitation with acetonitrile and analyzed by positive ion mode. Results: The linearity of the proposed method was investigated in the concentration range of 4-500 ng/mL (r = 0.9996) for OFL and 40-6000 ng/mL (r = 0.9998) for CEF. The lower limits of quantification were 4 ng/mL and 40 ng/mL for OFL and CEF respectively, which reach the level of both drugs possibly found in human plasma. Further, the reported method was validated as per the ICH guidelines and found to be well within the acceptable range. Conclusion: The proposed method is simple, rapid, accurate, precise, and appropriate for pharmacokinetic and therapeutic drug monitoring in the clinical laboratories.

Developing new method for quantifying pindolol by sequential injection analysis

An inexpensive, rapid, safe and green method for pindolol assay in medicines was developed using sequential injection analysis (SIA) technique. The method was based on the oxidation of pindolol by dichromate in sulfuric acid media. A chromogenic form of pindolol was spectrophotometrically detected at 640 nm. The 33 full-factorial design approach was applied to optimize acid concentration, pindolol volume and reaction time. The automation of SIA and the optimization process offered satisfactorily selectivity to the method. The recovery of pindolol in the presence of clopamide as a companion drug, besides excipients usually found in tablet formulation, was in the range of 96.5–98.4%. The automation also provided good repeatability, with a relative standard deviation value of 2.2% for seven replicates. Additionally, the miniaturization of SIA rendered the method reagent-saving (the total consumed reagent volumes was 120 μL) and environ-mentally-friendly (the total waste volume was 1320 μL). Furthermore, both the automation and miniaturization offered a rapid procedure (the sample frequency was 22 samples/h). On the other hand, the chemometric optimization improved the detectability of the method with the limits of detection and quantification of 0.57 and 1.9 μg/mL, respectively.

Multi-response optimization of sequential injection chromatographic method for determination of lisinopril and hydrochlorothiazide

Recently, a more efficient sequential injection chromatograph (SIC) with a high pressure selection valve has been developed at our laboratory. In the current work, the newly developed SIC system was exploited to optimize and validate a new method for the separation and quantification of lisinopril and hydrochlorothiazide in pharmaceutical preparations. A multi-response optimization study was conducted to screen the effect of mobile phase composition on resolution, reagent consumption, retention time, peak symmetry, peak height and baseline. The factorial design approach was adopted and the effect factors were determined. The SIC method has proven to be a competitor to high performance liquid chromatographic methods with respect to sample frequency, reagent consumption and safety for the environment, besides instrumentation benefits with respect to inexpensiveness, simplicity and portability. Short C18 monolithic columns (30 × 4.6 mm) were used to offer a rapid and reagent-saving procedure. Miniaturized fiber optic spectrometric devices were coupled with the SIC system to provide more instrumentation portability. Satisfactory separation, peak symmetry and theoretical plates were achieved. The SIC method was also accurate (the recovery range was 98.8–101.8%), precise (the RSD range was 0.95–2.29) and sensitive (the limits of detection were below 1.5 μg mL−1).

Development of a CZE Method for the Quantification of Pseudoephedrine and Cetirizine

Pseudoephedrine and cetirizine have been combined in dosage forms with more therapeutic benefits when compared with single-drug treatment. The current manuscript reports the development of the first capillary zone electrophoresis (CZE) assay method for that combination. The effects of pH and buffer concentration on resolution, noise, migration time and peak area were examined employing experimental design approach. The analytes were electropherographed into a 50.2 cm-long and 50 µm i.d. fused-silica capillary column using 10 mmol/L borate at pH 8.3 with a potential of 25 kV at 25°C and UV detection at 214 nm. The method was successfully validated in order to verify its suitability for pharmaceutical analysis for the purposes of quality control. Over previous high-performance liquid chromatographic methods, the current CZE method features the benefits of the use of cost-effective electrolyte, besides high sample throughput (11 samples/h). Furthermore, other analytical results including linear dynamic ranges, recovery (96.9-98.1%), intra- and interday precision (relative standard deviation ≤ 1.70%) as well as the limits of detection and quantification (≤2.65 µg/mL) were all satisfactory for the intended purpose.

Quadruple Response Factorial Design Optimization of Capillary Zone Electrophoresis Assay Procedure for Metformin and Sitagliptin Combination

The metformin–sitagliptin combination has been recently approved in 2012 for its better efficacy and safety for diabetes than using single drugs. The current manuscript describes an assay method for this recent combination by capillary zone electrophoresis (CZE). The factorial design optimization of electrolyte composition for quadruple response of resolution, migration time, peak area, and peak symmetry was conducted. The univarite method was applied for optimizing other electrophoretic conditions. The optimum electrolyte composition was 10 mM borate at pH 6.4. Sufficient separation with a resolution of 6.7 and peak symmetry of 0.932 and 0.985 were obtained. Satisfactory repeatability of migration time, peak area, peak height, and peak symmetry (RSD 0.16–2.4%) was obtained. The validation parameters were acceptable in terms of recovery, linearity, inter-mediate precision, limits of detection, and limits of quantification. The use of CZE provides reagent-saving and fast method comparing with reported HPLC methods.

High-throughput sequential injection assay method for chlorpromazine

This manuscript reports the optimization and validation of a new, rapid, reagent-saving and environmentally-safe method for chlorpromazine assay in pharmaceutical formulations utilizing sequential injection analysis (SIA) technique. Despite its benefits over univariate approach, chemometrics has been rarely exploited for optimizing SIA methods. Moreover, in those methods, some conditions have not been considered in optimization process. In the current study, more conditions, namely volumes and concentrations of reagents, have been optimized by chemometrics for the first time. A developing oxidation reaction of chlorpromazine by permanganate in acidic media was adopted. A spectrophotometric detection of the reduction of permanganate was applied at 526 nm using miniaturized fiber optic devices. The 24 full-factorial design and response surface approaches were exploited for method optimization. The method was validated and realized by a British Pharmacopoeia method. Experimental conditions and analytical aspects of the current SIA method were compared with those of a previous SIA method. Some analytical aspects were comparable while other aspects demonstrated better results from the current method than those from the previous one. The current method is rapid with a sample frequency of 51.4 samples/h. It is also reagent-saving with a total volume of consumed reagents and sample of 260 μL as well as environmental-safety with a total volume of waste production of 1260 μL. The method is therefore efficient for industrial-scale pharmaceutical analysis.