Hayam M. Lotfy

Comparative study of novel spectrophotometric methods manipulating ratio spectra: An application on pharmaceutical ternary mixture of omeprazole, tinidazole and clarithromycin

Three simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra are developed for simultaneous determination of omeprazole (OM), tinidazole (TN) and clarithromycin (CL) in tablets. Method A, is an extended ratio subtraction one (EXRSM). Method B is a ratio difference spectrophotometric one (RDSM), while method C is mean centering of ratio spectra (MCR). The calibration curves are linear over the concentration range of 1-20 μg/mL, 10-60 μg/mL and 0.25-1.0 mg/mL for OM, TN and CL, respectively. The specificity of the developed methods is investigated by analyzing laboratory prepared mixtures of the three drugs and their combined dosage form. Standard deviation values are less than 1.5 in the assay of raw materials and tablets. The three methods are validated as per ICH guidelines and accuracy, precision, repeatability and robustness are found to be within the acceptable limits.

Novel spectrophotometric methods for simultaneous determination of timolol and dorzolamide in their binary mixture

Two smart and novel spectrophotometric methods namely; absorbance subtraction (AS) and amplitude modulation (AM) were developed and validated for the determination of a binary mixture of timolol maleate (TIM) and dorzolamide hydrochloride (DOR) in presence of benzalkonium chloride without prior separation, using unified regression equation. Additionally, simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of the binary mixture namely; simultaneous ratio subtraction (SRS), ratio difference (RD), ratio subtraction (RS) coupled with extended ratio subtraction (EXRS), constant multiplication method (CM) and mean centering of ratio spectra (MCR). The proposed spectrophotometric procedures do not require any separation steps. Accuracy, precision and linearity ranges of the proposed methods were determined and the specificity was assessed by analyzing synthetic mixtures of both drugs. They were applied to their pharmaceutical formulation and the results obtained were statistically compared to that of a reported spectrophotometric method. The statistical comparison showed that there is no significant difference between the proposed methods and the reported one regarding both accuracy and precision.

Simultaneous determination of some cholesterol-lowering drugs in their binary mixture by novel spectrophotometric methods

Four simple, specific, accurate and precise spectrophotometric methods manipulating ratio spectra were developed and validated for simultaneous determination of simvastatin (SM) and ezetimibe (EZ) namely; extended ratio subtraction (EXRSM), simultaneous ratio subtraction (SRSM), ratio difference (RDSM) and absorption factor (AFM). The proposed spectrophotometric procedures do not require any preliminary separation step. The accuracy, precision and linearity ranges of the proposed methods were determined, and the methods were validated and the specificity was assessed by analyzing synthetic mixtures containing the cited drugs. The four methods were applied for the determination of the cited drugs in tablets and the obtained results were statistically compared with each other and with those of a reported HPLC method. The comparison showed that there is no significant difference between the proposed methods and the reported method regarding both accuracy and precision.

Development and validation of a modified QuEChERS protocol coupled to LC–MS/MS for simultaneous determination of multi-class antibiotic residues in honey

LC-MS/MS assay was developed and validated according to EU guidelines for determination of nitrofuran metabolites and nitroimidazole residues in honey. Crude samples were acid-treated to liberate matrix-bound residues and a modified QuEChERS protocol was employed. Nitrofurantoin, furazolidone, furaltadone and nitrofurazone were determined via analysis of their metabolites AHD, AOZ, AMOZ and SEM, respectively while nitroimidazole residues; ronidazole (RNZ) and dimetridazole (DMZ) were determined directly. For all analytes, neat standard calibration curves, after correction for matrix effect were successfully employed. Decision limit (CCα) and detection capability (CCβ) were below the MRPL for nitrofurans (1.00 μg kg(-1)) and the recommended concentration for nitroimidazole (3.00 μg kg(-1)), respectively. The CCα, CCβ, percentage recovery and CV% ranges were 0.12-0.74 μg kg(-1), 0.21-1.27 μg kg(-1), 90.96-104.80% and 2.65-12.58%, respectively. This work is part of the national initiative for establishing a national monitoring program for drug residues in Egyptian honey.

A comparative study of novel spectrophotometric methods based on isosbestic points; application on a pharmaceutical ternary mixture

This work represents the application of the isosbestic points present in different absorption spectra. Three novel spectrophotometric methods were developed, the first method is the absorption subtraction method (AS) utilizing the isosbestic point in zero-order absorption spectra; the second method is the amplitude modulation method (AM) utilizing the isosbestic point in ratio spectra; and third method is the amplitude summation method (A-Sum) utilizing the isosbestic point in derivative spectra. The three methods were applied for the analysis of the ternary mixture of chloramphenicol (CHL), dexamethasone sodium phosphate (DXM) and tetryzoline hydrochloride (TZH) in eye drops in the presence of benzalkonium chloride as a preservative. The components at the isosbestic point were determined using the corresponding unified regression equation at this point with no need for a complementary method. The obtained results were statistically compared to each other and to that of the developed PLS model. The specificity of the developed methods was investigated by analyzing laboratory prepared mixtures and the combined dosage form. The methods were validated as per ICH guidelines where accuracy, repeatability, inter-day precision and robustness were found to be within the acceptable limits. The results obtained from the proposed methods were statistically compared with official ones where no significant difference was observed.

Successive spectrophotometric resolution as a novel technique for the analysis of ternary mixtures of pharmaceuticals.

A novel spectrophotometric technique was developed for the simultaneous determination of ternary mixtures, without prior separation steps. This technique was called successive spectrophotometric resolution technique. The technique was based on either the successive ratio subtraction or successive derivative subtraction. The mathematical explanation of the procedure was illustrated. In order to evaluate the applicability of the methods a model data as well as an experimental data were tested. The results from experimental data related to the simultaneous spectrophotometric determination of lidocaine hydrochloride (LH), calcium dobesilate (CD) and dexamethasone acetate (DA); in the presence of hydroquinone (HQ), the degradation product of calcium dobesilate were discussed. The proposed drugs were determined at their maxima 202 nm, 305 nm, 239 nm and 225 nm for LH, CD, DA and HQ respectively; by successive ratio subtraction coupled with constant multiplication method to obtain the zero order absorption spectra, while by applying successive derivative subtraction they were determined at their first derivative spectra at 210 nm for LH, 320 nm or P(292-320) for CD, 256 nm or P(225-252) for DA and P(220-233) for HQ respectively. The calibration curves were linear over the concentration range of 2-20 μg/mL for both LH and DA, 6-50 μg/mL for CD, and 3-40 μg/mL for HQ. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs with no interference from other dosage form additives. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with those of the official BP methods for LH, DA, and CD, and with the official USP method for HQ; using student t-test, F-test, and one way ANOVA, showing no significant difference with respect to accuracy and precision.

Simultaneous determination of 200 pesticide residues in honey using gas chromatography-tandem mass spectrometry in conjunction with streamlined quantification approach.

A sensitive, accurate and reliable multi-class GC-MS/MS assay protocol for quantification and confirmation of 200 common agricultural pesticides in honey was developed and validated according to EU guidelines. A modified extraction procedure, based on QuEChERS method (quick, easy, cheap, effective, rugged and safe) was employed. Mass spectrophotometric conditions were individually optimized for each analyte to achieve maximum sensitivity and selectivity in MRM mode. The use of at least two reactions for each compound allowed simultaneous identification and quantification in a single run. The pesticides under investigation were separated in less than 31 min using the ultra-inert capillary column (DB-35MS). For all analytes, neat standard calibration curves in conjunction with correction for matrix effect were successfully employed. The detection limits of the assay ranged from 1.00 to 3.00 ng mL(-1) for the studied pesticides. The developed assay was linear over concentration range of 10.00-500.00 ng mL(-1), with correlation coefficient of more than 0.996. At the LOQ, 81% of the studied pesticides were efficiently recovered in the range of 70.00-120.00%, with CV% less than 15.00% while 99.3% compounds had mean percentage recovery of 60.00-140.00%, with CV% less than 21.00% (N=18, over three different days). The proposed assay was successfully applied for the analysis of the studied pesticide residues in one PT sample and 64 commercial honey samples collected over 1 year from different districts around Egypt. Results revealed that only one honey sample out of the 64 analyzed samples was contaminated with tau-Fluvalinate (10.00 μg kg(-1)). This wide scope assay protocol is applicable for monitoring pesticide residues in honey by national regulatory authorities and accredited labs; that should help ensure safety of such widely used product.

Development and validation of simultaneous spectrophotometric and TLC-spectrodensitometric methods for determination of beclomethasone dipropionate and salbutamol in combined dosage form

Spectrophotometric and TLC-spectrodensitometric methods were developed and validated for the simultaneous determination of beclomethasone dipropionate (BEC) and salbutamol (SAL). The spectrophotometric methods include dual wavelength, ratio difference, constant center coupled with a novel method namely, spectrum subtraction and mean centering with mean percentage recoveries and RSD 99.72±1.07 and 99.70±1.12, 100.25±1.12 and 99.89±1.12, 99.66±1.85 and 99.19±1.32, 100.74±1.26 and 101.06±0.90 for BEC and SAL respectively. The TLC-spectrodensitometric method was based on separation of both drugs on TLC aluminum plates of silica gel 60 F254, using benzene: methanol: triethylamine (10:1.5:0.5 v/v/v) as a mobile phase, followed by densitometric measurements of their bands at 230 nm. The mean percentage recoveries and RSD were 99.07±1.25 and 101.35±1.50 for BEC and SAL respectively. The proposed methods were validated according to ICH guidelines and were applied for the simultaneous analysis of the cited drugs in synthetic mixtures and pharmaceutical preparation. The methods were found to be rapid, specific, precise and accurate and can be successfully applied for the routine analysis of BEC and SAL in their pharmaceutical formulation with no need for prior separation. The results obtained were statistically compared to each other and to that of the reported HPLC method. The statistical comparison showed that there is no significant difference regarding both accuracy and precision.

Univariate versus Multivariate Spectrophotometric Methods for Simultaneous Determination of Complex Binary Mixtures with Overlapped Spectra: A Comparative Study

Two novel simple and accurate univariate spectrophotometric methods were described for the determination of a binary mixture of Sodium cromoglicate (SCG) and Fluorometholone (FLU) namely; ratio subtraction coupled with extended ratio subtraction (RS-EXRSM) and constant center (CCSM) spectrophotometric methods. The methods were able to recover the zero order absorption spectra of both drugs from their binary mixture through simple mathematical calculations. The linearity ranges were found to be (2.5–25 µg/mL) and (4- 25 µg/mL) for SCG and FLU, respectively. A comparative study was conducted between the proposed univariate methods versus multivariate ones, based on using principle component regression (PCR) and partial least squares (PLS-2). Upon applying the methods for the determination of SCG and FLU in laboratory prepared mixtures, the (CCSM and PLS-2) proved to be of higher predictive ability rather than (RS-EXRSM and PCR) in prediction of mixtures containing low concentration of one of the components. The proposed methods were validated in compliance with the ICH guidelines. These methods could be alternative to different HPLC techniques in quality control laboratories lacking the required facilities for those expensive techniques

Validated Stability Indicating Spectrophotometric Methods for the Determination of Lidocaine Hydrochloride, Calcium Dobesilate, and Dexamethasone Acetate in their Dosage Forms

Abstract Simple, specific, accurate and precise spectrophotometric methods were developed for determination of lidocaine hydrochloride, and calcium dobesilate in their binary mixture, or combined with dexamethasone acetate as a ternary mixture; in the presence of hydroquinone, the degradation product of calcium dobesilate without prior separation. In binary mixture lidocaine hydrochloride was determined using novel mathematical methods namely amplitude subtraction and amplitude factor, in addition to ratio subtraction coupled with first derivative. While dexamathasone acetate was assayed by first derivative method. Lidocaine and dexamethasone in ternary mixture could be determined by a novel resolution technique namely successive spectrophotometric resolution; including successive ratio subtraction coupled with either first derivative, or extended ratio subtraction for dexamethasone and ratio subtraction coupled with first derivative for lidocaine hydrochloride; and finally the calcium dobesilate could be determined by first derivative, derivative ratio and the novel modified amplitude subtraction methods. The calibration curves are linear over the concentration range of 2-20 µg mL-1 for both lidocaine hydrochloride and dexamethasone acetate, 2-19 µg mL-1 or 6-50 µg mL-1 for calcium dobesilate. The proposed methods could be successfully applied to commercial pharmaceutical preparations of the cited drugs. The proposed methods were validated according to the ICH guidelines. The obtained results were statistically compared with those of the reference reported methods using student t-test, F-test, and one way ANOVA, showing no significant difference with respect to accuracy and precision.AbstractSimple, specific, accurate and precise spectrophotometric methods were developed for determination of lidocaine hydrochloride, and calcium dobesilate in their binary mixture, or combined with dexamethasone acetate as a ternary mixture; in the presence of hydroquinone, the degradation product of calcium dobesilate without prior separation. In binary mixture lidocaine hydrochloride was determined using novel mathematical methods namely amplitude subtraction and amplitude factor, in addition to ratio subtraction coupled with first derivative. While dexamathasone acetate was assayed by first derivative method. Lidocaine and dexamethasone in ternary mixture could be determined by a novel resolution technique namely successive spectrophotometric resolution; including successive ratio subtraction coupled with either first derivative, or extended ratio subtraction for dexamethasone and ratio subtraction coupled with first derivative for lidocaine hydrochloride; and finally the calcium dobesilate could be ...