Comparing silver and gold nanoislands' surface plasmon resonance for bisacodyl and its metabolite quantification in human plasma.

Gold and silver nanoparticles have witnessed increased scientific interest due to their colourful colloidal solutions and exceptional applications. Comparing the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles is crucial for understanding and optimizing their optical properties. This comparison informs the design of highly sensitive plasmonic sensors, aids in selecting the most suitable nanoparticles for applications like surface-enhanced infrared spectroscopy (SEIRA) and biomedical imaging, and guides the choice between gold and silver nanoparticles based on their catalytic and photothermal properties. Ultimately, the study of LSPR facilitates the tailored use of these nanoparticles in diverse scientific and technological applications. Two SEIRA methods combined with partial least squares regression (PLSR) chemometric tools were developed. This development is based on the synthesis of homogeneous, high-dense deposited metal nanoparticle islands over the surface of glass substrates to be used as lab-on-chip SEIRA sensors for the determination of bisacodyl (BIS) and its active metabolite in plasma. SEM micrographs revealed the formation of metallic islands of colloidal citrate-capped gold and silver nanoparticles of average sizes of 29.7 and 15 nm, respectively. BIS and its active metabolite were placed on the nanoparticles' coated substrates to be directly measured, then PLSR chemometric modelling was used for the quantitative determinations. Plasmonic citrate-capped gold nanoparticle substrates showed better performance than those prepared using citrate-capped silver nanoparticles in terms of preparation time, enhancement factor, PLSR model prediction, and quantitative results. This study offers a way to determine BIS and its active metabolite in the concentration range 15-240 ng/mL in human plasma using inexpensive disposable glass-coated substrates that can be prepared in 1 h to get results in seconds with good recovery between 98.77 and 100.64%. The sensors provided fast, simple, selective, molecular-specific and inexpensive procedures to determine molecules in their pure form and biological fluid.

Electrochemical sensor based on bio-inspired molecularly imprinted polymer for sofosbuvir detection.

The electropolymerized molecularly imprinted polymers (MIP) have enabled the utilization of various functional monomers with superior selective recognition of the target analyte template. Methyldopa is an attractive synthetic dopamine analogue which has phenolic, carboxylic, and aminic functional groups. In this research, methyldopa was exploited to fabricate selective MIPs, for the detection of sofosbuvir (SFB), by a simple electropolymerization step onto a disposable pencil graphite electrode (PGE) substrate. The interaction between methyldopa, as a functional monomer, and a template has been investigated experimentally by UV spectroscopy. A polymethyldopa (PMD) polymer was electrografted onto PGE in the presence of SFB as a template. X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (ESI), and cyclic voltammetry (CV) were used for the characterization of the fabricated sensor. Differential pulse voltammetry (DPV) of a ferrocyanide/ferricyanide redox probe was employed to indirectly detect the SFB binding to the MIP cavities. The sensor shows a reproducible and linear response over a dynamic linear range from 1.0 × 10-11 M to 1.0 × 10-13 M of SFB with a limit of detection of 3.1 × 10-14 M. The sensor showed high selectivity for the target drug over structurally similar and co-administered interfering drugs, and this enabled its application to detect SFB in its pharmaceutical dosage form and in spiked human plasma samples.

A chemically modified solid-state sensor for magnesium(ii) ions and esomeprazole magnesium potentiometric assay.

The use of electrochemical sensors offers a simple, affordable solution with great reliability. Magnesium is a mineral that the body requires to function properly. It encourages preserving a stable pulse, strong bones, and healthy blood pressure. Herein, a novel ion-selective electrode using esomeprazole magnesium trihydrate as an ion-association complex was developed for magnesium(ii) ion determination in mineral water, drug substances, and pharmaceutical formulations. The electrode response was optimized in terms of plasticizer type, ion exchanger concentration, and membrane composition. To find the best sensor combination, the initial optimization research was performed using eight different sensors. A membrane containing 20% esomeprazole magnesium trihydrate, 36% carbon, and 44% o-Nitrophenyl Octyl Ether (NPOE) as a plasticizer yielded the best potentiometric response. The developed sensor demonstrated a Nernstian response with a slope of 29.93 ± 0.1 mV per decade in the concentration range of 1.41 × 10-5 mol L-1 to 1 × 10-2 mol L-1. Within a pH range of 5-8, it had a low detection limit of 4.13 × 10-6 mol L-1. When compared to the official method, there are no statistically significant differences.

Utility of Silver-nanoparticles for Nano Spectrofluorimetric Determination of Meropenem and Ertapenem: Bio-analytical Validation.

Bio-analytical, nano-quantitative spectrofluorimetric estimation of two non-classical ß-lactam antibiotics; meropenem (MP) and ertapenem (EP) is presented. The method is based on the enhancement of the fluorescence intensity of MP-Eu3+/EP-Eu3+ with silver nanoparticles (AgNPs). AgNPs were synthesized and characterized by UV and transmission electron microscope (TEM). The plasmon resonance produced an intense absorption maximum at 398.0 nm. TEM micrograph showed the particle morphology with an average particles size of 13.0 ± 2.95 nm. The fluorescence intensities were measured against blank reagents at λem of 396.0 nm and 405.0 nm after excitation at λex 305.0 nm and 303.0 nm for MP and EP, respectively. Under optimum conditions, the relative fluorescence intensity showed a good linear relationship with the concentration ranges of 4.0-14.0 and 4.0 -12.0 ng/mL with excellent correlation coefficients of 0.9998 and 0.9997, and limit of detection of 0.84 and 0.86 ng/mL for MP and EP, respectively. The method was successfully applied for direct analysis of MP and EP in their drug substances and pharmaceutical vials. The significant, sensitivity and practicality of the method facilitated MP detection in real plasma samples. Bio-analytical validation was performed according to FDA. The method was rectilinear over the ranges of, 5.0 -75.0 µg/mL plasma. Interestingly, this described system has a promising benefit for various applications exploiting the dramatically enhanced-fluorescence occurrence.

An electrochemical sensing platform to determine tetrahydrozoline HCl in pure form, pharmaceutical formulation, and rabbit aqueous humor.

In the pharmaceutical industry, finding cost-effective and real-time analyzers that provide valid data is a good aim. The purpose of this work was to propose a link between the pharmaceutical industry and the recent innovations in solid-contact ion-selective electrodes (SC-ISEs) for the utilization of these electrodes as real-time analyzers to evaluate the concentration of tetrahydrozoline HCl in different matrices. The backbone of these new potentiometric sensors is the conjunction of calix[6]arene and (2-hydroxypropyl)-ß-cyclodextrin as molecular recognition elements and a network of multi-walled carbon nanotubes as a solid transducer material between an ionophore-doped PVC membrane and microfabricated Cu electrodes. The proposed sensors were optimized to determine tetrahydrozoline, and their performances were assessed according to the IUPAC recommendations. The proposed solid-contact sensors were compared with liquid contact sensors, and the former sensors were found to be better than the latter sensors in terms of durability, handling, and easier adaptation to industry with comparable sensitivity. The measurements were implemented using phosphate buffer (pH: 6). The best obtained linearity range was 1 × 10-2 to 1 × 10-7 M, and the best LOD was 1 × 10-8 M. The sensors with the best performance were successfully applied to determine tetrahydrozoline in a pharmaceutical eye preparation and rabbit tears. The obtained results were statistically compared to those obtained by the official method of analysis, and no significant difference was obtained. The eco-score of the method was assessed using the eco-scale tool and also compared with that of the official method. The proposed approach was validated according to the International Council for Harmonisation (ICH) guidelines.

Stepwise optimization and sensitivity improvement of green micellar electrokinetic chromatography method to simultaneously determine some fluoroquinolones and glucocorticoids present in various binary ophthalmic formulations.

A sensitive micellar electrokinetic chromatography method is presented to simultaneously quantify ofloxacin, gatifloxacin, dexamethasone sodium phosphate and prednisolone acetate. The method has the advantages of being rapid, accurate, reproducible, ecologically acceptable and sensitive. The electrophoretic separation utilized 20 mm borate buffer as background electrolyte with pH 10.0 ± 0.1 and 50 mm sodium dodecyl sulfate as a micelle forming molecule. A capillary tube (50 µm i.d., 33 cm) of fused silica was used and on-column diode array detection at 243 nm for dexamethasone sodium phosphate and prednisolone acetate, and 290 nm for ofloxacin and gatifloxacin. Various factors were optimized such as the background electrolyte (type, concentration and pH), addition of sodium dodecyl sulfate and its concentration, detection wavelength, applied voltage and injection parameters. The studied drugs were efficiently separated in 6.2 min, at 20 kV with high resolution. The greenness of the method was estimated using an eco-scale tool and the presented method was found to have excellent green characteristics. The method was validated in conformance with International Conference on Harmonization guidelines, with acceptable accuracy, precision and selectivity. The suggested method can be employed for the economic analysis of the four drugs in dissimilar binary combinations of eye drops saving solvents and chemicals.

Simultaneous determination of phenazopyridine HCl and trimethoprim in presence of phenazopyridine HCl impurity by univariate and multivariate spectrophotometric methods - Quantification of phenazopyridine HCl impurity by univariate methods.

Three univariate and two multivariate spectrophotometric methods were developed and subsequently validated to determine phenazopyridine HCl (PHZ) and trimethoprim (TMP) in the presence of 2,6-Diaminopyridine (2,6-DAP). The first univariate method depends on direct determination of phenazopyridine by measuring its absorbance at 412 nm and performed in concentration range of 1.00-10.00 µg/mL. Then the contribution of phenazopyridine is removed by dividing the mixture spectrum with PHZ divisor (5 µg/mL) after that the constant is mathematically subtracted and finally the generated spectrum is multiplied with the PHZ divisor. These steps eliminate PHZ contribution and the recovered spectrum is that of TMP and 2,6-DAP only where different methods can be applied to determine TMP and 2,6-DAP through this binary mixture spectrum. The first method to determine both components depends on measuring both TMP and 2,6-DAP through their first derivative (1DD) spectra at 244.70 and 259.60 nm for TMP and 2,6-DAP, respectively with concentration ranges of 4.00-24.00 µg/mL TMP and 4.00-26.00 µg/mL 2,6-DAP. The second method depends on application of the isoabsorptive method which was used for TMP determination at its isoabsorptive point with 2,6-DAP at 242.64 nm with concentration range 1.00-20.00 µg/mL for TMP. The developed univariate methods were successfully applied to determine PHZ, TMP and PHZ impurity (2,6-DAP). Two multivariate methods were applied for determination of PHZ and TMP in presence of 2,6-DAP namely, Principle Component Regression (PCR) and Partial Least Squares (PLS). The results of the two models show that simultaneous determination of PHZ and TMP in presence of PHZ impurity can be performed in the concentration ranges of 6.00-14.00 µg/mL PHZ and 24.00-56.00 µg/mL TMP. All the proposed methods were successfully applied to analyze PHZ and TMP in pharmaceutical formulations without interference from the dosage form additives and the results were statistically compared with the reported method.

A Two-Step Optimization Approach: Validated RP-HPLC Method for Determination of Gatifloxacin and Dexamethasone in Ophthalmic Formulation.

The growing technology of stationary phase chemistry has a great impact on the chromatographic system performance and analysis economics. In this context, a simple rapid reversed phase high-performance liquid chromatography method development is presented for the analysis of gatifloxacin (GFN) and dexamethasone sodium phosphate (DSP) in their ophthalmic formulation. A two-step optimization approach has been conducted using optimum chromatographic conditions as well as proper selection of stationary phase. The chromatographic separation was carried out using sodium phosphate buffer pH 3.0 ± 0.1 and acetonitrile 72:28 v/v, respectively, with flow rate 1 mL min-1 and simultaneous detection at 243 nm. Three different column technologies were investigated at the optimum set of the chromatographic conditions: Xbridge® bridged ethylene hybrid silica, Kinetex™ Core-Shell and the Onyx™ Monolithic stationary phase. The monolithic column has shown better chromatographic separation, based on system suitability testing as well as shorter analysis time and sensitivity. The proposed method was validated according to International Conference on Harmonization guidelines. The linearity was achieved for GFN and DSP in the range 0.58-120 µg mL-1 and 0.50-120 µg mL-1, respectively, with acceptable accuracy, precision and selectivity.

Effect of Genetic Algorithm-Based Wavelength Selection as a Preprocessing Tool on Multivariate Simultaneous Determination of Paracetamol, Orphenadrine Citrate, and Caffeine in the Presence of p-Aminophenol Impurity.

BACKGROUND: The utilization of selection methods such as genetic algorithm (GA) aims to construct better partial least squares (PLS) and principal component regression (PCR) models than those established from the full-spectrum range. OBJECTIVE: Determination of paracetamol (PAR), orphenadrine citrate (Or.cit), and caffeine (CAF) in the presence of PAR nephrotoxic impurity [p-aminophenol (PAP)]. GA was applied to select the optimum wavelengths used. METHODS: A calibration set was prepared in which the three drugs, together with PAP, were modeled by multilevel multifactor design. This calibration set was used to build the PLS and PCR models, either with or without preprocessing the data using GA. RESULTS: Results were compared with and without preprocessing, and this revealed that GA can find an optimized combination of spectral wavelengths, yielding a lower root mean square error of prediction as well as a lower number of latent variables used. The results of the two models show that simultaneous determination of the aforementioned drugs can be performed in the concentration ranges of 20-60, 3-11, and 1-9 µg/mL for PAR, Or.cit, and CAF, respectively. CONCLUSIONS: The proposed models were applied for the determination of the three drugs in their pharmaceutical formulations, and the results were verified by the standard addition technique. HIGHLIGHTS: GA can be useful as a wavelength selection tool before applying multivariate PLS and PCR methods. GA gives an improvement in the predictive ability of the models with lower RMSEP and less number of latent variables (LVs). The proposed PLS, PCR, GA-PLS, and GA-PCR spectrophotometric methods were able to determine paracetamol, orphenadrine citrate, and caffeine in the presence of p-aminophenol and severe spectral overlapping.

Development and Validation of Chromatographic Methods for Simultaneous Determination of Paracetamol, Orphenadrine Citrate and Caffeine in Presence of P-aminophenol; Quantification of P-aminophenol Nephrotoxic Impurity Using LC-MS/MS.

Three chromatographic methods were developed, optimized and validated for Paracetamol (PAR), Orphenadrine citrate (Or.cit) and Caffeine (CAF) determination in their mixture and in presence of PAR toxic impurity; P-aminophenol (PAP) in tablets. The first method is based on a thin layer chromatography combined with densitometry. Separation was achieved using silica gel 60 F254 TLC plates and dichloromethane:methanol:acetone:glacial acetic acid (9:1:0.5:0.3, v/v/v) as a developing system at 230 nm. The second method is based on high-performance liquid chromatography with diode array detection. The proposed compounds are separated on a reversed phase C18 analytical column using phosphate buffer (pH 9; 0.05 M) and methanol (80:20, v/v) at 1.2 mL/min. Linear regressions are obtained in the range of 1-500 µg/mL, 25-1000 µg/mL and 1-400 µg/mL for PAR, Or.cit and CAF, respectively. Quantification of the toxic PAP is carried out using LC-MS-MS by electrospray ionization in the positive mode using triple quadrupole mass spectrometry. The limit of quantification for PAP is 1 ng/mL. All methods are validated according to the ICH guidelines and successfully applied to determine PAR, Or.cit, CAF and PAP in pure powder and in combined tablets dosage form without interference from excipients.

A Validated Ultra-Performance Liquid Chromatographic Method for the Simultaneous Determination of Nadifloxacin, Mometasone Furoate and Miconazole Nitrate in Their Combined Dosage Form and Spiked Human Plasma Samples.

Nadifloxacin, mometasone furoate and miconazole nitrate are formulated together as a topical antifungal dosage form. In this work, a reversed-phase ultra-performance liquid chromatographic method coupled with a diode array detector (RP-UPLC-DAD) was developed and validated to determine nadifloxacin, mometasone furoate and miconazole nitrate simultaneously in their bulk powder, in pharmaceutical preparation and in spiked human plasma samples. Separation was achieved on an ACQUITY UPLC C18 column of 2.2 µm particle size (2.1 × 100 mm) via isocratic elution using a mobile phase consisting of methanol, acetonitrile and water with ratio (50:20:30; v/v/v) and 0.1 g ammonium acetate, then pH was adjusted to (7.00) using acetic acid, flow rate 0.6 mL/min, temperature 30°C and UV detection at 220 nm. The method is linear in a range from 5 to 400 µg/mL for both nadifloxacin and miconazole nitrate and from 20 to 500 µg/mL for mometasone furoate. The method was validated according to the ICH guidelines then applied successfully to determine the mentioned drugs in their pharmaceutical preparation and spiked human plasma samples. For plasma samples, the results showed that the method can determine nadifloxacin, mometasone furoate and miconazole nitrate in human plasma samples with high accuracy and precision.

Comparing the predictability of different chemometric models over UV-spectral data of isoxsuprine and its toxic photothermal degradation products.

Isoxsuprine (ISX) is widely used for cerebral and peripheral vascular diseases. A comparative study was held among different multivariate calibration models for selective determination of a complex mixture of Isoxsuprine and four of its toxic photothermal degradation products that impair kidney and liver functions. The Partial Least Squares (PLS) and Artificial Neural Network (ANN) models were applied on the specific spectrum and on selected wavelengths using genetic algorithm (GA) technique as an efficient variable selection tool. The effect of GA on the model construction and performance was evaluated. The multilevel multifactor experimental design was adopted for the construction of the calibration set. Optimized parameters were used for the development of the different models. The performances of the developed models were assessed by predicting the concentration of eight different mixtures composing the validation set. Results were compared to one another and to the official method using one-way ANOVA statistical test to assure the validity of the constructed models. The lower chance of overfitting offered by ANN minimized the RMSEP relative to the PLS. On the other hand, the application of GA prior to model implementation affected the number of latent variables the prediction ability of both PLS and ANN models. The validated models were successfully applied as stability indicating assay methods for the selective determination of ISX and its photothermal degradation products in ISX raw material and market formulations.

Simultaneous Quantification of Chlorpheniramine, Phenylephrine, Guaifenesin in Presence of Preservatives with Detection of Related Substance Guaiacol in their Cough Syrup by RP-HPLC and TLC-Densitometric Methods.

Two sensitive chromatographic methods have been developed, and validated for chlorpheniramine maleate (CM), phenylephrine (PE) and guaifenesin (GF) determination in their mixture and in presence of GF related substance guaiacol (GL) and preservative namely; sodium benzoate (NaB). The first method was based on thin layer chromatographic separation (TLC) followed by densitometric determination of the separated spots. The separation was achieved using silica gel 60 F254 TLC plates and ethyl acetate: methanol: toluene: ammonia (7:1.5:1:0.5, by volume) as a developing system. Densitometric quantification of the three drugs was carried by the reflectance mode at 270 nm. The second method was based on the use of high-performance liquid chromatography with diode array detection, by which the proposed components were separated on a reversed phase C18 analytical column using phosphate buffer pH 2.9 (containing 0.1 g Heptane-1-sulphonic acid sodium salt) and acetonitrile (85:15, v/v) at 0.8 mL/min for 4 minutes then 1 mL/min till end of the run using flow rate online switching technique. Both methods were validated according to the ICH guidelines and successfully applied for the determination of CM, PE, and GF in pure powder and in combined cough syrup without interference from the excipients.

Analytical Eco-Scale for Assessing the Greenness of a Developed Potentiometric Method for Lomefloxacin Hydrochloride Determination in its Different Dosage Forms, Plasma, and Dissolution Medium.

Background: Traditional methods for Lomefloxacin hydrochloride (LOM) determination involve pretreatment steps, which extend analysis time and use hazardous chemicals. Objective: The ability to provide a rapid route without sample pretreatment for quantitative determination of compounds via a low-cost instrument is a challenging task. In this work, a simple potentiometric method was developed to determine the antibacterial LOM via in-house fabricated ion selective electrodes. Methods: Different sensors were fabricated using a poly vinyl chloride-based membrane, potassium tetrakis(4-chlorophenyl) borate as a cation exchanger, and 2-Nitrophenyl octyl ether as a plasticizer (sensor 1). To increase the selectivity of sensor 1, a selective molecular recognition component 2-hydroxypropyl-ß-cyclodextrin was used as ionophore (sensor 2). Results: The proposed method was validated according to International Union of Pure and Applied Chemistry recommendations, in which the proposed sensors show a linear dynamic range from 1 × 10-5 to 1 × 10-2 mol/L, with Nernstian slopes of 55.829 and 58.229 mV/decade for sensors 1 and 2, respectively. It was applied to determine LOM in bulk powder, in different dosage forms, and in plasma with no sample pretreatment. Also, the suggested method can be used as a green, in-line bench top real-time analyzer for in-process monitoring of LOM release from its tablets, under U.S. Food and Drug Administration dissolution regulations, with clear discrimination from common excipients. Results obtained by the proposed potentiometric method were compared with those obtained by a reported HPLC method. Conclusions: The proposed method is considered as a perfect alternative to traditional reported methods for LOM determination.

Multivariate Validated Models for Simultaneous Determination of Ibuprofen and Famotidine in the Presence of Related Substances.

Two multivariate validated spectrophotometric methods, namely partial least-squares (PLS) and principal component regression (PCR), were developed and validated for the determination of ibuprofen and famotidine in presence of famotidine degradation products and ibuprofen impurity (4-isobutylacetophenone). A calibration set was prepared in which the two drugs together with the degradation products and impurity were modeled using a multilevel multifactor design. This calibration set was used to build the PLS and PCR models. The proposed models successfully predicted the concentrations of both drugs in validation samples, with low root mean square error of cross validation (RMSECV) percentage. The method was validated by the estimate of the figures of merit depending on the net analyte signal. The results of the two models showed that the simultaneous determination of both drugs could be performed in the concentration ranges of 100-500 µg/mL for ibuprofen and 5-25 µg/mL for famotidine. The proposed multivariate calibration methods were applied for the determination of ibuprofen and famotidine in their pharmaceutical formulation, and the results were verified by the standard addition technique.

Zero and second-derivative synchronous fluorescence spectroscopy for the quantification of two non-classical ß-lactams in pharmaceutical vials: Application to stability studies.

The formation of metal chelates with various ligands may lead to the production of fluorescent chelates or enhance the fluorescence of the chelating agent. This paper describes two sensitive, selective and computer-solved methods, namely, zero order (SF) and second-derivative synchronous spectrofluorimetry (SDSFS) for nano-quantitation of two carbapenems; meropenem (MP) and ertapenem (EP). The methods are based on the chelation of MP with Tb3+ and EP with Zr4+ in buffered organic medium at pH 4.0 to produce fluorescent chelates. In the zero order method, the relative synchronous fluorescence intensity is measured at 327.0 nm at Δλ = 70.0 and 100.0 nm for MP and EP, respectively. The second method utilizes a second-derivative technique to enhance the method selectivity and emphasize a stability-indicating approach. The peak amplitudes (2 D) of the second-derivative synchronous spectra were estimated to be 333.06 and 330.06 nm for MP and EP, respectively. The proposed synchronous spectrofluorimetric methods were validated according to the International Conference on Harmonization (ICH) guidelines and applied successfully for the analysis of MP and EP in pure forms, pharmaceutical vials and in synthetic mixtures with different degradants of both drugs. Under optimum conditions, the mole-ratio method was applied and the co-ordination ratios of MP-Tb3+ and EP-Zr4+ chelates were found to be 1:1 and 1:3. The formation constants for the chelation complexes were evaluated using the Benesi-Hildebrand's equation; the free energy change (ΔG) was also calculated. The results indicated that EP-Zr4+ was more stable than the MP-Tb3+ chelate. Moreover, the developed methods were found to be selective and inexpensive for quantitative determination of both drugs in quality control laboratories at nano-levels.

Pharmacokinetic Evaluation of Empagliflozin in Healthy Egyptian Volunteers Using LC-MS/MS and Comparison with Other Ethnic Populations.

The present study considered the pharmacokinetic evaluation of empagliflozin after administration to Egyptian volunteers, and the results were compared with other ethnic populations. The FDA recognizes that standard methods of defining racial subgroups are necessary to compare results across pharmacokinetic studies and to assess potential subgroup differences. The design of the study was as an open labeled, randomized, one treatment, one period, single dose pharmacokinetic study. The main pharmacokinetic parameters estimated were Cmax, Tmax, t1/2, elimination rate constant, AUC0-t and AUC0-inf. The insignificant difference in pharmacokinetic parameters between Egyptians and white German subjects suggests that no dose adjustment should be considered with administration of 25 mg empagliflozin to Egyptian population. A new LC-MS/MS method was developed and validated, allowing sensitive estimation of empagliflozin (25-600 ng mL-1) in human plasma using dapagliflozin as an internal standard (IS). The method was applied successfully on the underlying pharmacokinetic study with enhanced sample preparation that involved liquid-liquid extraction. Multiple Reaction Monitoring (MRM) of the transition pairs of m/z 449.01 to 371.21 for empagliflozin and m/z 407.00 to 328.81 for dapagliflozin (IS) was employed utilizing negative mode Electro Spray Ionization (ESI). The validated LC-MS/MS method is suitable for further toxicodynamic and bioequivalence studies.

Spectrophotometric determination of meclizine hydrochloride and pyridoxine hydrochloride in laboratory prepared mixtures and in their pharmaceutical preparation.

In this paper, three rapid, simple, accurate and precise spectrophotometric methods were developed for the determination of meclizine hydrochloride in the presence of pyridoxine hydrochloride without previous separation. The methods under study are dual wavelength (DWL), ratio difference (RD) and continuous wavelet transform (CWT). On the other hand, pyridoxine hydrochloride (PYH) was determined directly at 291nm. The methods obey Beer's law in the range of (5-50µg/mL) for both compounds. All the methods were validated according to the ICH guidelines where the accuracy was found to be 98.29, 99.59, 100.42 and 100.62% for DWL, RD, CWT and PYH; respectively. Moreover the precision of the methods were calculated in terms of %RSD and it was found to be 0.545, 0.372, 1.287 and 0.759 for DWL, RD,CWT and PYH; respectively. The selectivity of the proposed methods was tested using laboratory prepared mixtures and assessed by applying the standard addition technique. So, they can be used for the routine analysis of pyridoxine hydrochloride and meclizine hydrochloride in quality-control laboratories.

Development and validation of HPLC and CE methods for simultaneous determination of amlodipine and atorvastatin in the presence of their acidic degradation products in tablets.

Two methods were developed for separation and quantitation of amlodipine (AML) and atorvastatin (ATV) in the presence of their acidic degradation products. The first method was a simple isocratic RP-HPLC method while the second was capillary electrophoresis (CE). Degradation products were obtained by acidic hydrolysis of the two drugs and their structures were elucidated for the first time by IR and MS spectra. Degradation products did not interfere with the determination of either drug and the assays were therefore stability-indicating. The linearity of the proposed methods was established over the ranges 1-50 µg mL-1 for AML and ATV in the HPLC method and in the range of 3-50 and 4-50 µg mL-1 for AML and ATV, respectively, in the CE method. The proposed methods were validated according to ICH guidelines. The methods were successfully applied to estimation of AML and ATV in combined tablets.

Stability-Indicating Method and LC-MS-MS Characterization of Forced Degradation Products of Sofosbuvir.

Sofosbuvir is a novel direct acting antiviral agent against hepatitis C virus. In the present work, a rapid, specific and reproducible isocratic reversed phase high performance liquid chromatography (RP-HPLC) method has been developed and validated for the determination of sofosbuvir in the presence of its stressed degradation products. Sobosbuvir was subjected to hydrolysis (acidic, alkaline and neutral), oxidation, photolysis and thermal stress, as per international conference on harmonization (ICH) conditions. The drug showed degradation under oxidative, photolysis, acid and base hydrolysis stress conditions. However, it was stable under thermal and neutral hydrolysis stress conditions. Chromatographic separation of the drug from its degradation products was performed on Inertsil ODS-3 C18 (250 mm × 4.6 mm i.d., 5 µm) column using a green mobile phase of methanol:water 70:30 (v/v). The degradation products were characterized by LC-MS-MS and the fragmentation pathways were proposed. The developed method was validated as per ICH guidelines. No previous method was reported regarding the degradation behavior of sofosbuvir.