Rasha M. Youssef

Spectrophotometric determination of binary mixtures of pseudoephedrine with some histamine H1-receptor antagonists using derivative ratio spectrum method

A derivative spectrophotometric method is developed for the assay of three binary mixtures of pseudoephedrine with fexofenadine (mix I), cetirizine (mix II) and loratadine (mix III). The method is based on the use of the first derivative of the ratio spectrum. The ratio spectrum was obtained by dividing the absorption spectrum of the mixture by that of one of the components. The concentration of the other component was determined from its respective calibration graph treated similarly. Moreover, the influence of Deltalambda for obtaining the first derivative of the ratio spectra and the effect of the divisor concentration on the calibration graphs were studied. The described method was applied for the determination of these combinations in synthetic mixtures and dosage forms. The results obtained were accurate and precise.

Simultaneous multiresidue determination of metronidazole and spiramycin in fish muscle using high performance liquid chromatography with UV detection

An efficient multiresidue method for the simultaneous determination of metronidazole (MET) and spiramycin (SPY) in tilapia fish muscle, based on high performance liquid chromatography with UV detection (HPLC-UV), has been developed. The drugs were extracted with 0.2% orthophosphoric acid-methanol (6:4), and the extracts were cleaned up on a solid phase extraction cartridge, C18 Sep-Pak light column. The LC separation was performed on a RP stainless-steel C-18 analytical column (150 mm x 4.6 mm, 5 microm) with a gradient elution system of 0.05 M phosphate buffer adjusted to pH 2.4-acetonitrile as the mobile phase at the flow rate of 1.0 ml min(-1). A wavelength programming was applied for the UV detection of the analytes. The method not only enabled the determination of the parent drugs, MET and SPY, but also permitted the determination of their metabolites, hydroxymetronidazole (HMET) and neospiramycin (NSPY). The calibration graphs for each drug were rectilinear in the range of 0.005-1.000 microg g(-1) for MET and HMET and 0.025-1.000 microg g(-1) for SPY and NSPY. With this method, the cited drugs with their metabolites were determined in fortified fish muscle tissues at levels of 0.025, 0.1 and 1.0 microg g(-1) with good accuracy and precision. LOD and LOQ obtained for each drug were as follows: 0.002 and 0.005 microg g(-1) for MET and HMET and 0.005 and 0.025 microg g(-1) for SPY and NSPY. Utilization of the method to successfully analyze tilapia fish muscle samples incurred with MET and SPY was described.

Spectrophotometric and titrimetric determination of nizatidine in capsules.

Four simple and accurate methods are described for the determination of nizatidine (NIZ) in pharmaceutical preparations. The first method is based on the formation of an ion-pair complex between the drug and either of bromocresol purple or picric acid with subsequent measurement of the developed colors at 411 and 400 nm, respectively. The second method depends on the condensation of mixed anhydrides of citric acid/acetic anhydride, with the tertiary amino group of the drug, where the developed color is measured spectrophotometrically at 545 nm. The oxidation of nizatidine by N-bromosuccinimide was utilized as a basis for the titrimetric method for its assay in capsules. The last method depends on the oxidation of nizatidine by ammonium cerium IV sulfate in the presence of perchloric acid with subsequent measurement of the absorbance at 314 nm; this principle is adopted to develop a kinetic method for the determination of NIZ in capsules. All the reaction conditions have been studied. The detection limits were varied from 0.44 to 0.78 microg ml(-1). The proposed methods were successfully applied to the assay of nizatidine in capsules.

Bioavailability study of triamterene and xipamide using urinary pharmacokinetic data following single oral dose of each drug or their combination.

An efficient chromatographic method for the simultaneous determination of triamterene (TRI) and xipamide (XIP) in urine samples, based on high performance liquid chromatography with photodiode array detector (HPLC-DAD) has been developed. The HPLC separation was performed on a RP stainless-steel C-18 analytical column (250 mm × 4.6 mm, 5 μm) with a gradient elution system of 0.05 M phosphate buffer adjusted to pH 4.0 and methanol as the mobile phase. The method was used to determine the urinary excretion profile and to calculate different urinary pharmacokinetic parameters following oral dose of their combination compared with single oral doses of each drug and hence comparing their bioavailability. Quantitation was performed using chlorthalidone as internal standard. The calibration graphs of each drug were rectilinear in the range of 0.2-40 μg/mL urine for TRI and 0.2-15 μg/mL urine for XIP. An HPLC-DAD method was also successfully developed for the simultaneous determination of the investigated drugs in pharmaceutical preparations. The methods were validated in terms of linearity, accuracy, precision, selectivity, limits of detection and quantitation and other aspects of analytical validation.

Enhanced spectrophotometric determination of two antihyperlipidemic mixtures containing ezetimibe in pharmaceutical preparations

Two spectrophotometric methods are presented for the simultaneous determination of ezetimibe/simvastatin and ezetimibe/atorvastatin binary mixtures in combined pharmaceutical dosage forms without prior separation. The first is the derivative ratio method where the amplitudes of the first derivative of the ratio spectra ((1) DD) at 299.5 and 242.5 nm were found to be linear with ezetimibe and simvastatin concentrations in the ranges 0.5-20 µgml(-1) and 1-40 µgml(-1) , respectively, whereas the amplitudes of the first derivative of the ratio spectra ((1) DD) at 289.5 and 288 nm were selected to determine ezetimibe and atorvastatin in the concentration ranges 5-50 µgml(-1) and 1-40 µgml(-1) , respectively. The second is the H-point standard additions method; absorbances at the two pairs of wavelengths, 228 and 242 nm or 238 and 248 nm, were monitored while adding standard solutions of ezetimibe or simvastatin, respectively. For the analysis of ezetimibe/atorvastatin mixture, absorbance values at 226 and 248 nm or 212 and 272 nm were monitored while adding standard solutions of ezetimibe or atorvastatin, respectively. Moreover, differential spectrophotometry was applied for the determination of ezetimibe in the two mixtures without any interference from the co-existing drug. This was performed by measurement of the difference absorptivities (ΔA) of ezetimibe in 0.07 M 30% methanolic NaOH relative to that of an equimolar solution in 0.07 M 30% methanolic HCl at 246 nm. The described methods are simple, rapid, precise and accurate for the determination of these combinations in synthetic mixtures and dosage forms.

Simultaneous determination of montelukast and fexofenadine using Fourier transform convolution emission data under non- parametric linear regression method.

New hybrid chemometric method has been applied to the emission response data. It deals with convolution of emission data using 8-points sin xi polynomials (discrete Fourier functions) after the derivative treatment of these emission data. This new application was used for the simultaneous determination of Fexofenadine and Montelukast in bulk and pharmaceutical preparation. It was found beneficial in the resolution of partially overlapping emission spectra of this mixture. The application of this chemometric method was found beneficial in eliminating different types of interferences common in spectrofluorimetry such as overlapping emission spectra and self- quenching. Not only this chemometric approache was applied to the emission data but also the obtained data were subjected to non-parametric linear regression analysis (Theil’s method). The presented work compares the application of Theil’s method in handling the response data, with the least-squares parametric regression method, which is considered the de facto standard method used for regression. So this work combines the advantages of derivative and convolution using discrete Fourier function together with the reliability and efficacy of the non-parametric analysis of data. Theil’s method was found to be superior to the method of least squares as it could effectively circumvent any outlier data points.New hybrid chemometric method has been applied to the emission response data. It deals with convolution of emission data using 8-points sin xi polynomials (discrete Fourier functions) after the derivative treatment of these emission data. This new application was used for the simultaneous determination of Fexofenadine and Montelukast in bulk and pharmaceutical preparation. It was found beneficial in the resolution of partially overlapping emission spectra of this mixture. The application of this chemometric method was found beneficial in eliminating different types of interferences common in spectrofluorimetry such as overlapping emission spectra and self- quenching. Not only this chemometric approache was applied to the emission data but also the obtained data were subjected to non-parametric linear regression analysis (Theil’s method). The presented work compares the application of Theil’s method in handling the response data, with the least-squares parametric regression method, which is considered the de facto standard method used for regression. So this work combines the advantages of derivative and convolution using discrete Fourier function together with the reliability and efficacy of the non-parametric analysis of data. Theil’s method was found to be superior to the method of least squares as it could effectively circumvent any outlier data points.

Experimental design and machine learning strategies for parameters screening and optimization of Hantzsch condensation reaction for the assay of sodium alendronate in oral solution

An experimental design was adopted to attain the optimum reaction parameters of chemical derivatization of anhydrous sodium alendronate in an oral solution formula via Hantzsch condensation reaction. All reaction controlling variables, namely, time of reaction, temperature, reagent ratio and volume and buffer type, pH and volume were studied using the Plackett–Burman screening design to determine significant variables. Reaction temperature and pH of the buffer solution were found to be significant variables. Optimization was performed using the central composite design to get the optimum levels of these variables. Moreover, a comparison was made with artificial neural networks and support vector machines. The same results were obtained with low percentage relative error. After carrying out the spectrophotometric analysis, interferences from oral solution excipients were eliminated with a simple extraction procedure before measuring the absorbance at 340 nm. Satisfactory results of sample analysis were obtained and they were in good agreement with the label claim. A linear calibration graph of absorbance versus concentration was obtained with very low value of intercept and high value of correlation coefficient (0.9999) in the range of 2.44–34.10 μg mL−1. The proposed spectrophotometric method was fully validated in accordance with ICH guidelines. Statistical comparison with a reported reference method showed similar results with respect to accuracy and precision.

Development and validation of spectrophotometric and HPTLC methods for simultaneous determination of rosiglitazone maleate and metformin hydrochloride in the presence of interfering matrix excipients

Abstract Two simple methods have been developed and validated for the simultaneous determination of rosiglitazone maleate (ROS) and metformin hydrochloride (MET) in synthetic mixtures and coated tablets in a ratio of 1:250 (ROS:MET). The first method was a spectrophotometric one. The minor component, ROS was determined by measuring the values of absorbance at λmax 312 nm and the D1 amplitudes at 331 nm where MET shows no absorption contribution. However, absorbance interferences from tablet excipients were successfully corrected by D1 at 331 nm zero-crossing technique. Study of spectral interference from tablet excipients was included in the text. Standard curves for Amax and D1 methods were in the concentration range 20.0–80.0 μg mL−1. The major component, MET was determined both in binary mixtures and tablets by measuring its Amax at 236 nm. Extensive dilution eliminated any absorption contribution from the coexisting ROS or tablet matrix. Standard curves showed linearity in the concentration range 4.0–12.8 μg mL−1. The second method was based on high performance thin layer chromatography (HPTLC) separation of the two drugs followed by densitometric measurements of their spots at 230 nm. The separation was carried out on Merck HPTLC aluminium sheets of silica gel 60 F254 using methanol:water:NH4Cl 1% w/v (5:4:1 v/v/v) as the mobile phase. Linear calibration graphs of peak area values were obtained versus concentrations in the range of 0.4–2.0 μg band−1 and 20.0–100.0 μg band−1 for ROS and MET, respectively. According to International Conference on Harmonisation (ICH) guidelines, different validation parameters were verified for the two methods and presented.

High-performance thin-layer chromatographic assay of metformin in urine using ion-pair solid-phase extraction: Application for bioavailability and bioequivalence study of new microbeads controlled release formulation

A sensitive high-performance thin-layer chromatographic (HPTLC) method was developed for the estimation of metformin in human urine. The drug was extracted from urine using ion-pair solid-phase extraction (IPSPE). Separation was carried out on Merck HPTLC aluminum sheets of silica gel 60 F254 using a mixture of chloroform-methanol-ammonia 27% w/v (5:5:0.2, v/v) as a mobile phase. This system was found to give dense and compact spots for metformin (retardation factor, RF, 0.25) following densitometric measurements of the spots at 237 nm. The proposed method was applied to generate urinary excretion data for metformin after administration of two metformin formulations (500 mg extended release, XR, Formulation R, and microbeads controlled release, Formulation T) to six healthy human volunteers in a two-treatment, crossover design. Various pharmacokinetic parameters like peak excretion rate ((dAU/dt)max), cumulative amount (Ae0–24) of metformin excreted, elimination half-life (t1/2), and terminal elimination rate constant (kel) were calculated for both the formulations. Statistical comparison of various pharmacokinetic parameters of Formulation T with that of Formulation R revealed that Formulation T is bioequivalent with Formulation R.

Development of a stability indicating HPLC-DAD method for the simultaneous determination of mometsone furoate and salicylic acid in an ointment matrix

A validated stability-indicating method has been developed for the simultaneous determination of mometsone furoate (MOM) and salicylic acid (SAA) in a combined dosage form. This method is based on the reversed-phase high performance liquid chromatographic (HPLC) separation of the cited drugs. The HPLC separation was performed on a RP Zobrax Eclipse XDB-C8 analytical column (150 × 4.6 mm, 5 μm) with isocratic elution with a mobile phase of methanol and 0.02 M aqueous phosphate buffer (70 : 30) adjusted to pH 2.3 and a flow rate of 1.5 mL min−1. Quantitation was achieved by means of photodiode array detection (DAD) at 260 nm. The calibration graphs for each drug were rectilinear in the range of 0.25–15 and 12.5–750 μg mL−1 for MOM and SAA, respectively using dexamethasone acetate as the internal standard. The proposed HPLC-DAD method was successfully applied in the determination of the investigated drugs in ointment. The method was validated in compliance with ICH guidelines, in terms of linearity, accuracy, precision, robustness, limits of detection and quantitation and specificity.