Miriam F. Ayad

Validation of different spectrophotometric methods for determination of vildagliptin and metformin in binary mixture.

New, simple, specific, accurate, precise and reproducible spectrophotometric methods have been developed and subsequently validated for determination of vildagliptin (VLG) and metformin (MET) in binary mixture. Zero order spectrophotometric method was the first method used for determination of MET in the range of 2-12 μg mL(-1) by measuring the absorbance at 237.6 nm. The second method was derivative spectrophotometric technique; utilized for determination of MET at 247.4 nm, in the range of 1-12 μg mL(-1). Derivative ratio spectrophotometric method was the third technique; used for determination of VLG in the range of 4-24 μg mL(-1) at 265.8 nm. Fourth and fifth methods adopted for determination of VLG in the range of 4-24 μg mL(-1); were ratio subtraction and mean centering spectrophotometric methods, respectively. All the results were statistically compared with the reported methods, using one-way analysis of variance (ANOVA). The developed methods were satisfactorily applied to analysis of the investigated drugs and proved to be specific and accurate for quality control of them in pharmaceutical dosage forms.

New methods for amlodipine and valsartan native spectrofluorimetric determination, with factors optimization study.

Four native fluorescence methods were suggested for simultaneous determination of amlodipine (AML) and valsartan (VAL). These methods were based on excitation of both drugs at λ(ex) 300 nm, in one step, to give maximum emission at λ(em) 378 and 496 nm for AML and VAL, respectively. The first method, single λ(ex) method, was used without any additions. The sensitivity of this method was further increased by the addition of hydroxy propylmethyl cellulose (HPMC) surfactant, β-cyclodextrin, or ferric oxide magnetite nanoparticles, in the other three methods. Different types of surfactants, and different concentration levels of both β-cyclodextrin and ferric oxide nanoparticles, were scanned to determine the optimum conditions for enhancing the sensitivity. Some factors affecting the fluorescence intensity of both cited drugs, like the type and volume of the added solvent (to be used as a sensing agent), and pH of measurement were studied and optimized. The proposed methods could be used in determination of AML and VAL in bulk powder, their laboratory prepared mixtures and pharmaceutical formulations. The obtained results were statistically compared to each other and to that of some reported methods. The specificity of the developed methods was investigated, and the methods were validated according to ICH guidelines.

Investigation of different spectrophotometric and chemometric methods for determination of entacapone, levodopa and carbidopa in ternary mixture

New, simple, accurate and sensitive UV spectrophotometric and chemometric methods have been developed and validated for determination of Entacapone (ENT), Levodopa (LD) and Carbidopa (CD) in ternary mixture. Method A is a derivative ratio spectra zero-crossing spectrophotometric method which allows the determination of ENT in the presence of both LD and CD by measuring the peak amplitude at 249.9nm in the range of 1-20μgmL-1. Method B is a double divisor-first derivative of ratio spectra method, used for determination of ENT, LD and CD at 245, 239 and 293nm, respectively. Method C is a mean centering of ratio spectra which allows their determination at 241, 241.6 and 257.1nm, respectively. Methods B and C could successfully determine the studied drugs in concentration ranges of 1-20μgmL-1 for ENT and 10-90μgmL-1 for both LD and CD. Methods D and E are principal component regression and partial least-squares, respectively, used for the simultaneous determination of the studied drugs by using seventeen mixtures as calibration set and eight mixtures as validation set. The developed methods have the advantage of simultaneous determination of the cited components without any pre-treatment. All the results were statistically compared with the reported methods, where no significant difference was observed. The developed methods were satisfactorily applied to the analysis of the investigated drugs in their pure form and in pharmaceutical dosage forms.

Two smart spectrophotometric methods for the simultaneous estimation of Simvastatin and Ezetimibe in combined dosage form.

Two simple, accurate, precise, sensitive and economic spectrophotometric methods were developed for the simultaneous determination of Simvastatin and Ezetimibe in fixed dose combination products without prior separation. The first method depends on a new chemometrics-assisted ratio spectra derivative method using moving window polynomial least square fitting method (Savitzky-Golay filters). The second method is based on a simple modification for the ratio subtraction method. The suggested methods were validated according to USP guidelines and can be applied for routine quality control testing.

Application of New Spectrofluorometric Techniques for Determination of Atorvastatin and Ezetimibe in Combined Tablet Dosage Form

Two accurate, reliable, and highly sensitive spectrofluorometric methods were developed for simultaneous determination of the binary mixture of Atorvastatin and Ezetimibe without prior separation steps. The first method is based on double scan synchronous fluorescence spectrometry. Each of Atorvastatin and Ezetimibe can be determined independent of the other when scanned at Δλ=100 nm and 40 nm, respectively. The relative fluorescence intensity-concentration plots at two wavelengths, 272 (Δλ=100 nm) and 266 nm (Δλ=40 nm) were rectilinear over the range of 0.4-8 µg/mL (for Atorvastatin) and 0.6-8 µg/mL (for Ezetimibe), respectively. The second method is based on the technique of simultaneous equations (Vierodts method), in which two equations are solved simultaneously after using a single excitation wavelength of 273 nm and λEm1=380 nm of Atorvastatin and λEm2=301 nm of Ezetimibe. Under the optimum conditions, linear relationships were found between the relative fluorescence intensity and the concentrations of the investigated drugs in the range of 0.4-8 µg/mL (for Atorvastatin) 0.6-8 µg/mL (for Ezetimibe). The different experimental parameters affecting the fluorescence intensities of the two drugs were carefully studied and optimized. The proposed methods were successfully applied for the determination of the investigated drugs in pure form, dosage form and in synthetic mixtures with good recovery and the results obtained were favorably compared to those obtained with a reference method.

Optimization of Extraction, HPLC and Kinetic Studies for Determination of Some Food Tainting Compounds in Different Food Matrices

Solid-liquid extraction, ultrasonic-assisted extraction and matrix solid-phase dispersion (MSPD) were optimized and compared in terms of recoveries for the simultaneous extraction of indole (IND) and 2,4-dichlorophenol (DCP) from catfish samples and for the extraction of IND alone from potato samples. Applying high-performance liquid chromatography (HPLC-DAD) procedure using mobile phase of methanol : water (65 : 35) at 280 nm, MSPD was the method of choice for the extraction of IND and DCP from catfish and, also, for IND from potato. The extraction recoveries of MSPD were in the range (97.9-99.7%) and (99.8-100.6%); for IND and DCP, respectively, in catfish samples and (98.4-99.7%) for IND alone in potato samples. Solid-phase extraction (SPE) was chosen the method of choice for the extraction of DCP from fish farms water samples after optimization and comparison with direct sample injection and extraction recoveries were in the range (97.9-100.3%). Kinetics were further studied to follow each of production of IND in catfish during storage at different temperatures and uptake of DCP by tilapia in fish farms water samples using MSPD-HPLC and SPE-HPLC, respectively.

Simultaneous Determination of Octinoxate, Oxybenzone, and Octocrylene in a Sunscreen Formulation Using Validated Spectrophotometric and Chemometric Methods.

Accurate, reliable, and sensitive spectrophotometric and chemometric methods were developed for simultaneous determination of octinoxate (OMC), oxybenzone (OXY), and octocrylene (OCR) in a sunscreen formulation without prior separation steps, including derivative ratio spectra zero crossing (DRSZ), double divisor ratio spectra derivative (DDRD), mean centering ratio spectra (MCR), and partial least squares (PLS-2). With the DRSZ technique, the UV filters could be determined in the ranges of 0.5-13.0, 0.3-9.0, and 0.5-9.0 μg/mL at 265.2, 246.6, and 261.8 nm, respectively. By utilizing the DDRD technique, UV filters could be determined in the above ranges at 237.8, 241.0, and 254.2 nm, respectively. With the MCR technique, the UV filters could be determined in the above ranges at 381.7, 383.2, and 355.6 nm, respectively. The PLS-2 technique successfully quantified the examined UV filters in the ranges of 0.5-9.3, 0.3-7.1, and 0.5-6.9 μg/mL, respectively. All the methods were validated according to the International Conference on Harmonization guidelines and successfully applied to determine the UV filters in pure form, laboratory-prepared mixtures, and a sunscreen formulation. The obtained results were statistically compared with reference and reported methods of analysis for OXY, OMC, and OCR, and there were no significant differences with respect to accuracy and precision of the adopted techniques.

Enhanced LC–MS/MS analysis of alogliptin and pioglitazone in human plasma: Applied to a preliminary pharmacokinetic study

A new fast LC-MS/MS method was developed for determination of alogliptin and pioglitazone in human plasma. Linearity ranges of 10-400ngmL-1 for alogliptin and 25-2000ngmL-1 for pioglitazone, were found to be suitable for their bioanalysis covering the Cmin and Cmax values of the drugs. Direct precipitation technique was used for simultaneous extraction of the drugs successfully from human plasma samples. Chromatographic separation was achieved on a BEH C18 column (50mm×2.1mm, 1.7μm) with 0.1% aqueous formic acid: acetonitrile (40:60, v/v) at a flow rate of 0.3mLmin-1. The validated method was applied to a preliminary pharmacokinetic study on human volunteers. Monitoring the transition pairs of m/z 340.18 to 116.08 for alogliptin and m/z 356.99 to 133.92 for pioglitazone, using triple quadrupole mass spectrometer with multiple reaction monitoring, was achieved in the positive mode. The validated method is accurate and suitable for further clinical applications and possible bioequivalence studies.

Validated chemometrics-assisted spectrophotometric methods for simultaneous determination of bisphenol-A-diglycidyl ether and some of its reaction products in canned foods in the Egyptian market

Two multivariate calibration methods, namely principal component regression (PCR) and partial least squares (PLS-2) have been developed, validated and compared for the simultaneous determination of bisphenol-A-diglycidyl ether (BADGE) and some of its reaction products, including BADGE·HCl·H2O, BADGE·H2O and BADGE·2HCl. Chemometrics allowed rapid, accurate and precise simultaneous quantification of the analytes of interest which was not possible by other spectrophotometric methods due to their severe spectral overlap. PCR and PLS-2 techniques successfully quantified BADGE, BADGE·HCl·H2O, BADGE·H2O and BADGE·2HCl in the ranges of 1.4-3.4, 1-5, 1-4.2 and 1-7 μg mL-1, respectively. The constructed models were validated according to the International Conference on Harmonization guidelines and successfully applied for the determination of these compounds in pure form, laboratory prepared mixtures and in various types of canned foods following the limits and regulations of the European Union (EU) where satisfactory recovery results were obtained.

Mimicking new receptors based on molecular imprinting and their application to potentiometric assessment of 2,4-dichlorophenol as a food taint

Innovative host-tailored polymers were prepared, characterized and used as recognition elements in potentiometric transducers for the selective quantification of 2,4-dichlorophenol (DCP).The polymer beads were synthesized using DCP as a template molecule, acrylamide (AM),methacrylic acid (MAA) and ethyl methacrylate (EMA) as functional monomers and divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA) as cross-linkers. The sensors were fabricated by the inclusion of MIPs in plasticized polyvinyl chloride (PVC) matrix. Response characteristics of the proposed sensors revealed anionic slopes of -59.2, -49.7 and -80.6 mV/decade with detection limits of 5.6 × 10-5,5.9 × 10-5 and 13.2 × 10-5 mol/L for MIP/AM/DVB, MIP/MAA/DVB and MIP/EMA/EGDMA membrane based sensors, respectively. Good selectivity was observed over common inorganic/organic anions. Validation of the assay method according to IUPAC recommendations was justified ensuring the synthesis of good reliable novel sensors for DCP determination. The method was successfully applied for routine analysis of food taint in fish and fish farms water samples.