Mohamed R. Elghobashy

Simultaneous determination of metformin hydrochloride and pioglitazone hydrochloride in binary mixture and in their ternary mixture with pioglitazone acid degradate using spectrophotometric and chemometric methods

In this work two well known oral hypoglycemic drugs that are administered in combination for patients with type-II diabetes were simultaneously determined. Several spectrophotometric methods were developed and validated for the determination of metformin hydrochloride (MET), pioglitazone hydrochloride (PIO) and pioglitazone acid degradate (PIO Deg). Derivative, ratio derivative, isosbestic and chemometric-assisted spectrophotometric methods were developed. The first derivative (D(1)) method was used for the determination of MET in the range of 5-30 microg x mL(-1) and PIO in the range of 10-90 microg x mL(-1) by measuring the peak amplitude at 247 nm and 280 nm, respectively. The concentration of PIO was calculated directly at 268 nm. The first derivative of ratio spectra (DD(1)) method used the peak amplitudes at 238 nm and 248.6 nm for the determination of MET in the range of 5-30 microg x mL(-1). In the isosbestic point method (ISO), the total mixture concentration was calculated by measuring the absorbance at 254.6 nm. Classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS-2) were used for the quantitative determination of MET, PIO and PIO Deg. The methods developed have the advantage of simultaneous determination of the cited components without any pre-treatment. Resolution and quantitative determination of PIO degradate with a minimum concentration of 3 microg x mL(-1) in drug samples was done. The proposed methods were successfully used to determine each drug and the acid degradate in a laboratory-prepared mixture and pharmaceutical preparations. The results were statistically compared using one-way analysis of variance (ANOVA). The methods developed were satisfactorily applied to the analysis of the two drugs in pharmaceutical formulations.

Application of Membrane-Selective Electrodes for the Determination of Pioglitazone Hydrochloride in the Presence of Its Acid Degradant or Metformin Hydrochloride in Tablets and Plasma

Abstract Polyvinyl chloride (PVC) membrane sensors for the determination of pioglitazone hydrochloride (PIO) and metformin hydrochloride (MET) were described by using the ion association complexes between these drugs with either sodium tetraphenyl-borate (TPB) or ammonium reineckate (RNC) counter ions. The performance characteristics of the sensors were evaluated according to IUPAC recommendations, reveal a fast, stable and linear response over the concentration range 3.162 × 10−5 − 1 × 10−2 M for PIO and 1 × 10−3 − 1 × 10−1 M for MET. The sensors are used for determination of PIO and MET in tablets and plasma. The developed method was found to be simple, accurate and precise when compared with the reported method.

Spectrophotometric Methods for Simultaneous Determination of Sofosbuvir and Ledipasvir (HARVONI Tablet): Comparative Study with Two Generic Products

Sofosbuvir and ledipasvir are the first drugs in a combination pill to treat chronic hepatitis C virus. Simple, sensitive, and rapid spectrophotometric methods are presented for the determination of sofosbuvir and ledipasvir in their combined dosage form. These methods were based on direct measurement of ledipasvir at 333 nm (due to the lack of interference of sofosbuvir) over a concentration range of 4.0-14.0 µg/mL, with a mean recovery of 100.78 ± 0.64%. Sofosbuvir was determined, without prior separation, by third-derivative values at 281 nm; derivative ratio values at 265.8 nm utilizing 5.0 µg/mL ledipasvir as a divisor; the ratio difference method using values at 270 and 250 nm using 5.0 µg/mL ledipasvir as a divisor; and the ratio subtraction method using values at 261 nm. These methods were found to be linear for sofosbuvir over a concentration range of 5.0-35.0 µg/mL. The suggested methods were validated according to International Conference on Harmonization guidelines. Statistical analysis of the results showed no significant difference between the proposed methods and the manufacturers LC method of determination with respect to accuracy and precision. These methods were used to compare the equivalence of an innovator drug dosage form and two generic drug dosage forms of the same strength.

Successive ratio subtraction coupled with constant multiplication spectrophotometric method for determination of hydroquinone in complex mixture with its degradation products, tretinoin and methyl paraben.

A sensitive and selective stability-indicating successive ratio subtraction coupled with constant multiplication (SRS-CM) spectrophotometric method was studied and developed for the spectrum resolution of five component mixture without prior separation. The components were hydroquinone in combination with tretinoin, the polymer formed from hydroquinone alkali degradation, 1,4 benzoquinone and the preservative methyl paraben. The proposed method was used for their determination in their pure form and in pharmaceutical formulation. The zero order absorption spectra of hydroquinone, tretinoin, 1,4 benzoquinone and methyl paraben were determined at 293, 357.5, 245 and 255.2 nm, respectively. The calibration curves were linear over the concentration ranges of 4.00-46.00, 1.00-7.00, 0.60-5.20, and 1.00-7.00 μg mL(-1) for hydroquinone, tretinoin, 1,4 benzoquinone and methyl paraben, respectively. The pharmaceutical formulation was subjected to mild alkali condition and measured by this method resulting in the polymerization of hydroquinone and the formation of toxic 1,4 benzoquinone. The proposed method was validated according to ICH guidelines. The results obtained were statistically analyzed and compared with those obtained by applying the reported method.

Novel ratio difference at coabsorptive point spectrophotometric method for determination of components with wide variation in their absorptivities.

Different methods have been introduced to enhance selectivity of UV-spectrophotometry thus enabling accurate determination of co-formulated components, however mixtures whose components exhibit wide variation in absorptivities has been an obstacle against application of UV-spectrophotometry. The developed ratio difference at coabsorptive point method (RDC) represents a simple effective solution for the mentioned problem, where the additive property of light absorbance enabled the consideration of the two components as multiples of the lower absorptivity component at certain wavelength (coabsorptive point), at which their total concentration multiples could be determined, whereas the other component was selectively determined by applying the ratio difference method in a single step. Mixture of perindopril arginine (PA) and amlodipine besylate (AM) figures that problem, where the low absorptivity of PA relative to AM hinders selective spectrophotometric determination of PA. The developed method successfully determined both components in the overlapped region of their spectra with accuracy 99.39±1.60 and 100.51±1.21, for PA and AM, respectively. The method was validated as per the USP guidelines and showed no significant difference upon statistical comparison with reported chromatographic method.

Application of normal fluorescence and stability-indicating derivative synchronous fluorescence spectroscopy for the determination of gliquidone in presence of its fluorescent alkaline degradation product

Simple, smart and sensitive normal fluorescence and stability-indicating derivative synchronous spectrofluorimetric methods have been developed and validated for the determination of gliquidone in the drug substance and drug product. Normal spectrofluorimetric method of gliquidone was established in methanol at λ excitation 225nm and λ emission 400nm in concentration range 0.2-3μg/ml with LOD equal 0.028. The fluorescence quantum yield of gliquidone was calculated using quinine sulfate as a reference and found to be 0.542. Stability-indicating first and third derivative synchronous fluorescence spectroscopy were successfully utilized to overcome the overlapped spectra in normal fluorescence of gliquidone and its alkaline degradation product. Derivative synchronous methods are based on using the synchronous fluorescence of gliquidone and its degradation product in methanol at Δ λ50nm. Peak amplitude in the first derivative of synchronous fluorescence spectra was measured at 309nm where degradation product showed zero-crossing without interference. The peak amplitudes in the third derivative of synchronous fluorescence spectra, peak to trough were measured at 316,329nm where degradation product showed zero-crossing. The different experimental parameters affecting the normal and synchronous fluorescence intensity of gliquidone were studied and optimized. Moreover, the cited methods have been validated as per ICH guidelines. The peak amplitude-concentration plots of the derivative synchronous fluorescence were linear over the concentration range 0.05-2μg/ml for gliquidone. Limits of detection were 0.020 and 0.022 in first and third derivative synchronous spectra, respectively. The adopted methods were successfully applied to commercial tablets and the results demonstrated that the derivative synchronous fluorescence spectroscopy is a powerful stability-indicating method, suitable for routine use with a short analysis time. Statistical comparison between the results obtained by normal fluorescence and derivative synchronous methods and the official one using students t-test and F-ratio showed no significant difference regarding accuracy and precision.

Stability-indicating chromatographic determination of hydroquinone in combination with tretinoin and fluocinolone acetonide in pharmaceutical formulations with a photodegradation kinetic study

Two sensitive and selective stability-indicating methods were developed for simultaneous determination of the active pharmaceutical ingredient hydroquinone in combination with tretinoin and fluocinolone acetonide in their pure forms and within the pharmaceutical formulation. Method A was based on a gradient elution liquid chromatographic (HPLC) determination of the active ingredients, their degradation products (hydroquinone polymer, 1,4-benzoquinone, isotretinoin and fluocinolone acetonide photodegradation) and in the presence of the preservatives methyl and propyl parabens found in pharmaceutical formulations. Method B was a thin layer chromatography (TLC)-densitometry method using a chiral developing system for the separation and determination of the active ingredients, isotretinoin, the preservatives and 1,4-benzoquinone. The molecular weight of the hydroquinone polymer formed from its alkali degradation was characterized by gel permeation chromatography. The mechanism of fluocinolone acetonide photodegradation in acetonitrile at 254 nm was studied using single crystal X-ray diffraction. The degradation products, hydroquinone polymer and isotretinoin, were found in one batch of the pharmaceutical formulation analyzed near its expiry date. The proposed HPLC method was also used for a comparative kinetic study of the photodegradation of the active ingredients. Hydroquinone showed reversible zero order kinetics, tretinoin and fluocinolone acetonide followed complex kinetic reactions in acetonitrile within two hours. The results obtained were statistically analyzed and compared with those obtained by applying the manufacturers method.

Smart electrochemical sensing platform for the simultaneous determination of psychotic disorder drugs isopropamide iodide and trifluoperazine hydrochloride

A novel, simple and highly sensitive sensor for the simultaneous determination of isopropamide iodide (ISP) and trifluoperazine hydrochloride (TFP) was developed. A carbon paste electrode was modified with m-cresol purple (MCP) and carboxylated multiwalled carbon nanotubes (MWCNTs). Different techniques were used to characterize the nanostructure and performance of the sensor. Under the optimized experimental conditions, ISP and TFP showed linear responses over the ranges of 5.50 × 10−6–1.70 × 10−4 and 5.00 × 10−7–1.34 × 10−3 mol L−1, respectively. The detection limits for ISP and TFP were found to be 9.91 × 10−7 mol L−1 and 1.10 × 10−7 mol L−1, respectively. Satisfactory recoveries of analytes from these samples were demonstrated, indicating that the suggested sensor is highly suitable for clinical analysis, quality control and routine determination of ISP and TFP in pharmaceutical formulations and human fluids.

Comparative stability-indicating chromatographic methods for determination of 4-hexylresorcinol in pharmaceutical formulation and shrimps

Graphical abstract Figure. No Caption available. HighlightsHPLC, UPLC–MS/MS and TLC‐densitometric determination of 4‐Hexylresorcinol in presence of degradation products.Methods applied in pharmaceuticals and shrimps.Impurities determined by HPLC.Degradation mechanism studied and identified by LC–MS/MS. Abstract Three chromatographic stability‐indicating methods were developed for determination of 4‐hexylresorcinol in pure form and in a pharmaceutical formulation. Method A was based on a gradient elution liquid chromatographic HPLC determination of 4‐hexylresorcinol, its related impurities and in presence of its degradation products. UPLC–MS/MS (Method B) was described for determination of the cited drug in presence of its degradation products. Method C was a thin‐ layer chromatography (TLC)‐densitometry method for the separation and determination of the active ingredient, one of its related impurities and in presence of its degradation products. The mechanism of alkali, oxidative and photodegradation of 4‐hexylresorcinol was studied according to ICH guidelines. The degradation products were characterized by the LC–MS/MS method. Methods A and B were applicable for determination of 4‐hexylresorcinol residues in shrimp meat. The studied drug was easily degraded in alkali medium giving toxic compounds. The results obtained by the proposed methods were statistically analyzed and compared with those obtained by applying a reported method.

Chromatographic Determination of Aminoacridine Hydrochloride, Lidocaine Hydrochloride and Lidocaine Toxic Impurity in Oral Gel

Two sensitive and selective analytical methods were developed for simultaneous determination of aminoacridine hydrochloride and lidocaine hydrochloride in bulk powder and pharmaceutical formulation. Method A was based on HPLC separation of the cited drugs with determination of the toxic lidocaine-related impurity 2,6-dimethylaniline. The separation was achieved using reversed-phase column C18, 250 × 4.6 mm, 5 µm particle size and mobile phase consisting of 0.05 M disodium hydrogen phosphate dihydrate (pH 6.0 ± 0.2 adjusted with phosphoric acid) and acetonitrile (55 : 45, v/v). Quantitation was achieved with UV detection at 240 nm. Linear calibration curve was in the range of 1.00-10.00, 13.20-132.00 and 1.32-13.20 µg mL(-1) for aminoacridine hydrochloride, lidocaine hydrochloride and 2,6-dimethylaniline, respectively. Method B was based on TLC separation of the cited drugs followed by densitometric measurement at 365 nm on the fluorescent mode for aminoacridine hydrochloride and 220 nm on the absorption mode for lidocaine hydrochloride. The separation was carried out using ethyl acetate-methanol-acetic acid (65 : 30 : 5 by volume) as a developing system. The calibration curve was in the range of 25.00-250.00 ng spot(-1) and 0.99-9.90 µg spot(-1) for aminoacridine hydrochloride and lidocaine hydrochloride, respectively. The results obtained were statistically analyzed and compared with those obtained by applying the manufacturers method.