Search

A micellar electrokinetic capillary chromatography (MEKC) method has been developed and validated for simultaneous analysis of febuxostat and its related substances in active pharmaceutical ingredients and pharmaceutical formulations. Analysis was performed in an uncoated fused silica capillary (34 cm effective length, 50 μm diameter). Method sensitivity was enhanced using an extended light path capillary, with an optical path 150 μm and the choice of 320 nm detector operat-ing wavelength due to lower background noise and higher selectivity. BGE consisted of 20 mM borate buffer pH 9.3 and 50 mM SDS and 2% acetonitrile. Analysis was performed at 30 kV separation voltage and 32 °C capillary temperature. The method was linear over the range 1.0–10.0 μg mL−1 for each impurity corresponding to reporting limits regarding the ICH Q3A guidelines. The method has proven to be selective, precise, accurate and robust. Proposed MEKC method has been successfully applied for the quantitative determination of febuxostat and purity assay of active pharmaceutical ingredient and tablet dosage forms.

Background Sodium Valproate is the sodium salt of valproic acid (VPA). Valproic acid is mainly used for the treatment of epilepsy. The specific aim of the study is to develop and validate an optimized method for the determination of six related substances such as N,N-dimethyl valpronamide, valeric acid, 2-methyl valeric acid, 2-ethyl valeric acid, 2-isopropyl valeric acid and 2-n-butyl valeric acid in Sodium Valproate Oral Solution by Gas Chromatography. Chromatographic separations of these six related substances were achieved on DB-FFAP fused silica capillary column (30 m × 0.53 mm) bonded with a 0.5-µm layer of macrogol 20,000 2-nitroterephthalate materials used as stationary phase. The six related impurities were extracted using heptane and monitored by Gas Chromatography coupled with flame ionization detector. The performance of the developed method was assessed by evaluating system suitability, method precision, specificity, linearity and range, ruggedness, accuracy, robustness. Results The correlation coefficient was within the acceptance criteria in the range of 0.9998. The evaluated concentrations for Sodium Valproate were in the ranges of 5.05–25.27 ppm. The average recovery values were in the range of 92.4–100.4%. Solution Stability experiments were performed to evaluate the degradation behavior of SVS. Conclusion A novel, precise and sensitive GC method was developed, validated and optimized for the determination of six related substances in sodium Valproate oral solution. The results obtained from the validation experiments demonstrated that the method is accurate, precise, linear, specific, sensitive and robust. Hence, the proposed method can be an alternative method, for the determination of related substances in sodium valproate oral solution drug substance.

Introduction. Docetaxel is widely used for cancer treatment. Actual issue for newly developed polymer-based Docetaxel formulations is applicability of current quality requirements. The technology of polymeric forms, including gamma-sterilization, are differ from actual Docetaxel injections technology. In this study were used PLGA-based particles with Docetaxel. The main attention was directed to studying qualitative and quantitative content of related impurities in polymeric forms during long-term storage and gamma-sterilization in comparison with pharmacopoeial requirements for Docetaxel injections.Aim. Studying of possible patterns of Docetaxel-related impurities formation between intact and gamma-irradiated batches.Materials and methods. Objects of study – lyophilizates of Docetaxel polymeric forms was previously obtained by the authors. Qualitative and quantitative analysis was performed by high pressure liquid chromatography.Results and discussion. Docetaxel-related impurities was determined and evaluated in the intact and gamma-treated batches. It was cleared, that related substances in the gamma-treated batches was different in comparison with non-treated but after vary storage periods.Conclusion. Docetaxel-loaded polymeric drugs shown proper stability during long term storage. The influence of gamma-treatment to Docetaxelrelated impurities content was found. Gamma sterilization can be promising method for novel drugs, but it needs individual study in the each case.

Clonazepam contains one benzodiazepine ring in its chemical structure which makes it vulnerable to degradation. In this study, green analytical chemistry approach was applied in attempts for the development of validated stability indicating RP-HPLC method for determining clonazepam and its related substances in pharmaceutical formulation. Validation has been performed according to ICH guidelines. Assay was capable of simultaneous monitoring of the intact drug in the presence of its related substances within the same run. HPLC assay involved an ODS column and a mobile phase composed of 2% sodium dodecyl sulfate, 0.05 M sodium acetate buffer pH 3.5 and isopropanol in ratio (25:55:20) at a flow rate of 1.5 mL/min and detection was carried out at 254 nm. HPLC method allowed good resolution between the peaks that corresponded to the active pharmaceutical ingredients and its degradation products with good linearity, precision, accuracy, specificity, LOD and LOQ. The expanded uncertainty (0.33%) of the method was also estimated from method validation data. This analytical technique is not only ecofriendly but also faster than the conventional liquid chromatographic system official in the USP-36. Keywords: Green analytical chemistry, Clonazepam, Related substances, Uncertainty, HPLC, Stability indicating method

A critical step in the production of Esomeprazole powder for solution is a period between the filling process and lyophilization, where all vials, partially closed, are completely exposed to environmental influences. Excessive instability reflects in pH value variations caused by oxygen’s impact. In order to provide pH control, which consequently affects drug stability, Esomeprazole batches, produced in the same way, were kept in partially closed vials for 3 h at temperatures of 20 °C and −30 °C, after which they were lyophilized and stored for long-term stability for 36 months. The aim of the presented study was to apply a deep-learning algorithm for the prediction of the Esomeprazole stability profile and to determine the pH limit for the reconstituted solution of the final freeze-dried product that would assure a quality product profile over a storage period of 36 months. Multilayer perceptron (MLP) as a deep learning tool, with four layers, was used. The pH value of Esomeprazole solution and time of storage (months) were inputs for the network, while Esomeprazole assay and four main impurities were outputs of the network. In order to keep all related substances and Esomeprazole assay in accordance with specifications for the whole shelf life, the pH value for the reconstituted finish product should be set in the range of 10.4–10.6.

A sensitive and selective method was developed for the separation and characterization of related substances (RSs) in EVT-401 by hyphenated LC–MS techniques. Complete separation of the RSs was achieved with an Inertsil ODS-SP column (250 mm×4.6 mm, 5 µm) by linear gradient elution using a mobile phase consisting of 0.2% formic acid solution, methanol and acetonitrile. EVT-401 was found to be susceptible to acid, alkaline and oxidative stresses, while relatively stable under photolytic and thermal dry stress conditions. Fourteen RSs including six process-related substances and eight degradation products were detected and identified in EVT-401 with positive ESI high-resolution TOF-MS analysis of their parent ions and the corresponding product mass spectra elucidation, and some of them were further verified by chemical synthesis and NMR spectroscopy. The specific LC–MS method developed for separation, identification and characterization of RSs is valuable for EVT-401 manufacturing process optimization and quality control.

A simple, rapid and sensitive ultrahigh performance liquid chromatographic method was developed for the determination of the anti-diabetic drug: empagliflozin (EMPA) and three related substances in spiked human plasma, using dapagliflozin (DAPA) as an internal standard and tetrahydrofuran as a plasma protein precipitating agent. The chromatographic separation was achieved on an Acquity “UPLC® BEH” C18 column (50 mm × 2.1 mm i.d, 1.7 µm particle size), and a mobile phase consisting of aqueous trifluoroacetic acid (0.1%, pH 2.5): acetonitrile (60:40, v/v) at a flow rate of 0.5 mL/min. Upon using the UPLC system, the run time could be reduced to less than 1.2 min, and the solvents consumption decreased to 0.36 mL of acetonitrile per run. The response was linear over a concentration range of 50–700 ng/mL and 40–200 ng/mL (r2 = 0.9994–0.9999) with lower limits of detection and quantification (LOD/LOQ) of 15/50, 11.5/40, 12/40 and 12.5/40 ng/mL for EMPA and the three related substances, respectively. Good accuracy was obtained with mean percentage recoveries ≥ 96.97% for the studied compounds. The method was validated according to the ICH guidelines and was found suitable for routine analysis of EMPA and its related substances in human plasma. Electronic supplementary material The online version of this article (10.1186/s13065-019-0604-9) contains supplementary material, which is available to authorized users.

As a new dosage form, coenzyme Q10 (Co-Q10) soft capsules are easily absorbed and utilized by the human body. Co-Q10 soft capsules can effectively improve the bioavailability and reduce medical costs for patients. A main concern about Co-Q10 as an active pharmaceutical ingredient (API) is how to control the total quantity of related substances. In this article, according to the degradation pattern of the API, the most easily degradable impurity (impurity X) in the sample was prepared and its chemical structure was determined. Furthermore, a simple and accurate method was developed for the determination of related substances and to avert the interference of excipient ingredients in Co-Q10 soft capsules. The approach was validated adequately and the primary impurity X was confirmed accurately. The limit of total quantity of related substances (less than 1%) could be revised to the level of specific impurity X being no more than 0.5%, in this effective quality control method of Co-Q10 soft capsules. The revised level is suggested to be included in the corresponding standard of the supplement taken from the Pharmacopoeia of the People&rsquo, s Republic of China (2015 edition). This can provide a feasible method for the relevant enterprises and regulatory authorities to control the related substances of coenzyme Q10 soft capsules.

A suitable liquid chromatography quadrupole time-of-flight mass spectrometric (LC–Q-TOF–MS) method was developed for separation and characterization of related substances in bacitracin test drug. The separation was performed on LiChrospher RP-18 column using methanol as mobile phase A and 0.2% ammonium acetate buffer solution as mobile phase B in gradient elution. A total of 12 related substances were detected through high resolution mass spectrometric determination in a positive electrospray ionization mode. They were identified as co-existing active components and degradation products of bacitracin through the analysis and elucidation of both the protonated parents and the product ions of all the related substances and their fragmentation pathways were also proposed.

Objective: To develop a highly sensitive LC-MS/MS (liquid chromatography-mass spectrometry/mass spectrometry)method applied to the detection and quantitation of UDCA (ursodeoxycholic acid) related substances such as CA (cholic acid), DCA(deoxycholic acid), CDCA (chenodeoxycholic acid) and LCA (lithocholic acid) in raw material and pharmaceutical formulation.Methods: The method was validated for specificity, linearity, accuracy, precision, robustness. A triple quadrupole mass detector wasemployed, equipped with an ESI (electrospray ionization) source operated in the negative ion mode. The chromatographic systemconsisted of a Symmetry C18 column (150 mm × 4.6 mm, id; particle size 5 µm) and methanol-acetonitrile-ammonium acetate (pH 7.6;10 mM) (40:40:20, v/v/v) as the mobile phase. The chromatographic conditions were 25 uL injection volume, flow rate of 0.4 mL/minand column temperature set at 35 °C. Key findings: The method requires a minimum sample amount and presents very low LOD(limits of detection) for CA (0.29 ng/mL), DCA (0.59 ng/mL), CDCA (0.13 ng/mL) and LCA (0.44 ng/mL) in comparison to LCmethods coupled to different detectors like UV (ultraviolet), fluorescence and refractive index. Conclusions: The developed andvalidated LC-MS/MS method for the determination of UDCA and related substances in raw material and in a suspension wasadvantageous since it required a minimum sample amount. In turn, it could be used as a stability indicating method. Fil: Boscolo, Oriana. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina Fil: Flor, Sabrina Andrea. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química Analítica; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina Fil: Dobrecky Ceciclia. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología; Argentina Fil: Martinefski, Manuela Romina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica. Cátedra de Química Analítica; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina Fil: Tripodi, Valeria Paula. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina Fil: Lucangioli, Silvia Edith. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina

A novel simple, direct and selective gas chromatography–mass spectrometry (GC/MS) procedure was developed for the determination of the antihistamine drug dimenhydrinate (DMH) in presence of six of its related substances and potential impurities, namely, diphenylmethane, diphenylmethanol, benzophenone, orphenadrine, caffeine and 8-chlorocaffeine. The method involved resolution of the underivatized compounds using a trifluoropropylmethyl polysiloxane (Rtx-200) capillary column and the mass spectrometric detection was carried out in the electron-impact (EI) mode. Excellent baseline separation of DMH and the cited related substances was achieved in less than 15min. Quantification of the parent drug DMH was based on measuring its peak area. The reliability and analytical performance of the proposed method were validated with respect to linearity, range, precision, accuracy, specificity, robustness, detection and quantification limits. Calibration curve of DMH was linear over the range 50–500μg/mL with determination coefficient (R2)=0.9982. The proposed method was successfully applied for the assay of DMH in tablets dosage form with recoveries>96.80%.

Lopinavir is an antiretroviral drug used for the inhibition of HIV protease. Four related substances of lopinavir were observed during the manufacturing process of lopinavir in the laboratory and they were identified. The present work describes the origin, synthesis, characterization, and control of these related substances.

A simple and rapid ultra - high performance liquid chromatographic (UHPLC) method for the separation and determination of oxcarbazepine and its related substances in tablets, was developed. Chromatographic separation of oxcarbazepine from its related substances (degradation and by-products) was achieved on a reversed phase C18 column (Pinnacle DB C18, RESTEK, 100 x 2.1 mm, 1.9 μm particle size) using gradient program with water (as mobile phase A) and acetonitrile (as mobile phase B), at a flow rate 0.5 mL min-1 and UV detection at 254 nm. The column temperature was 30°C.The method has good selectivity towards oxcarbazepine and its related substances. The accuracy of the method for oxcarbazepine assay, expressed as mean recovery was 101.8 %, and of the method for quantification of degradation products was 95.9 % - 103.3 %. Limit of quantification for oxcarbazepine and its degradation products ranged from 0.60 μg mL-1 to 1.30 μg mL-1. The linearity range for oxcarbazepine assay was from 2.4 to 3.60 mg mL-1 (R2=0.999). Mean value for oxcarbazepine assay from the tablets was 299.92 mg (label claim 300 mg). The method can be used for routine analysis and the quality control of oxcarbazepine drug substance and its formulated products.

An isocratic, sensitive and stability-indicating high performance liquid chromatographic (HPLC) method for separation and determination of the related substances of micafungin sodium was developed. The chromatographic separation was achieved on Agilent Zorbax SB-C18 column (250 × 4.6 mm, 5 μm). Forced degradation study confirmed that the newly developed method was specific and selective to the degradation products. The performance of the method was validated according to the present ICH guidelines for specificity, linearity, accuracy, precision and robustness. Regression analysis showed correlation coefficient value greater than 0.999 for micafungin sodium and its six impurities. Limit of detection of impurities was in the range of 0.006%–0.013% indicating the high sensitivity of the newly developed method. Accuracy of the method was established based on the recovery obtained between 98.2% and 102.0% for all impurities. RSD obtained for the repeatability and intermediate precision experiments, was less than 1.0%. The method was successfully applied to quantify related substances of micafungin sodium in bulk drugs.

Cefixime is an important cephalosporin antibiotic that easily decomposes and releases different related substances in preparation and storage steps. The objective of the current study was to develop a simple, precise, and accurate isocratic liquid chromatography (LC) method for the determination of cefixime in the presence of its related substances generated from thermal stress in the bulk drug. The chromatographic conditions were comprised of a reversed-phase C18 column (4.6 × 250 mm, 5 μm) with a mobile phase composed of water: acetonitrile (85:15 v/v, with 0.5% formic acid) and ultraviolet detection (UV). Some thermal degradation products were identified using a proposed liquid chromatography-mass spectrometry method. Five peaks (A, B, C, D, and E impurities based on British Pharmacopoeia) were known and a few unknown peaks appeared in the thermal stress solution of cefixime. The linear regression analysis data for the calibration plot of the LC-UV method showed a good linear relationship in the concentration range 0.9-1000.0 μg mL(-1). The recovery of the optimized method was between 94.6 and 98.4% and the inter- and intra-day relative standard deviations were less than 3.3%. The obtained results shown in the LC-UV proposed method can be conveniently used in a quality control laboratory for routine analysis of cefixime for the assay and related substances, as well as for the evaluation of stability samples of bulk drugs.

A stability-indicating liquid chromatographic method has been developed and validated for the determination of Diltiazem Hydrochloride (DTZ) together with its six related substances (Diltiazem sulphoxide, Imp-A, Imp-B, Imp-D, Imp-E, and Imp-F) in a laboratory mixture as well as in a novel tablet formulation developed in-house. Efficient chromatographic separation was achieved on a Hypersil BDS C18 (150 mmÃ4.6 mm, 5.0 μm) with mobile phase containing 0.2% Triethylamine (TEA) in gradient combination with acetonitrile (ACN) at a flow rate of 1.0 mL/min and the eluent was monitored at 240 nm. In the developed method, the resolution of DTZ from any pair of impurities was found to be greater than 2.0. The test solution and related substances were found to be stable in the diluent for 24 h. The developed method resolved the drug from its known impurities, stated above, and also from additional impurities generated when the formulation was subjected to forced degradation; the mass balance was found close to 99.9%.Regression analyses indicate correlation coefficient value greater than 0.997 for DTZ and its six known impurities. The LOD for DTZ and the known impurities was at a level below 0.02%. The method has shown good, consistent recoveries for DTZ (99.8â101.2%) and also for its six known impurities (97.2â101.3%). The method was found to be accurate, precise, linear, specific, sensitive, rugged, robust, and stability-indicating. Keywords: Diltiazem Hydrochloride, Benzodiazepine, Stability-indicating, Related substances, ICH guidelines, HPLC

Objective : Telmisartan is a potent, long-lasting, nonpeptide antagonist of the angiotensin II type-1 (AT 1 ) receptor that is indicated for the treatment of essential hypertension. Hydrochlorothiazide is a widely prescribed diuretic and it is indicated for the treatment of edema, control of essential hypertension and management of diabetes insipidus. In the current article a new, accurate, sensitive, precise, rapid, reversed phase high performance liquid chromatography (RP-HPLC) method was developed for determination of related substances of Telmisartan and Hydrochlorthiazide in tablet dosage form. Materials and Methods : Simultaneous determination of related substances was performed on Kromasil C 18 analytical column (250 × 4.6 mm; 5΅m pertical size) column at 40°C employing a gradient elution. Mobile phase consisting of solvent A (solution containing 2.0 g of potassium dihydrogen phosphate anhydrous and 1.04 g of Sodium 1- Hexane sulphonic acid monohydrate per liter of water, adjusted to pH 3.0 with orthophosphoric acid) and solvent B (mixture of Acetonitrile: Methanol in the ratio 80:20 v/v) was used at a flow rate of 1.0 ml min−1 . UV detection was performed at 270 nm. Results : During method validation parameter such as precision, linearity, accuracy, specificity, limit of detection and quantification were evaluated, which remained within acceptable limits. Conclusions : HPLC analytical method is linear, accurate, precise, robust and specific, being able to separate the main drug from its degradation products. It may find application for the routine analysis of the related substances of both Telmisartan and Hydrochlorthiazide in this combination tablets.

A sensitive, precise, specific, linear and stability indicating isocratic HPLC method was developed for the analysis of related substances in zolmitriptan. The potential known related substances are (S)-4-(4-aminobenzyl)-1,3-oxazolidin-2-one (impurity I) and (S)-4-(4-hydrazinobenzyl)-1,3-oxazolidin-2-one (impurity II). The method can be used for the detection and quantification of known and unknown impurities and degradants in the drug substance zolmitriptan during routine analysis and also for stability studies in view of its capability to separate degradation products.

A new micellar electrokinetic capillary chromatographic (MEKC) method has been developed for simultaneous quantitation of atorvastatin and its related substances. The separation was carried out in an extended light path capillary at applied voltage of 30 kV using a background electrolyte consisting of 10 mM sodium tetraborate buffer pH 9.5, 50 mM sodium dodecyl sulphate and 20% (v/v) methanol. The addition of methanol to the running buffer resulted in a very effective choice to achieve resolution between the peaks of charged substances adjacent to atorvastatin as well as the peaks of neutral drug-related substances. Linear calibration curves were established over the concentration range 100-1200 µ ; ; g mL-1 for atorvastatin and 1.0-12.5 µ ; ; g mL-1 for related substances. The proposed MEKC procedure has been validated with respect to selectivity, precision, linearity, limits of detection, and quantitation, accuracy and robustness. The method has been successfully applied to the determination of atorvastatin and purity evaluation of bulk drug and formulated products.

Fondaparinux sodium is a synthetic low-molecular-weight heparin (LMWH). This medication is an anticoagulant or a blood thinner, prescribed for the treatment of pulmonary embolism and prevention and treatment of deep vein thrombosis. Its determination in the presence of related impurities was studied and validated by a novel ion-pair HPLC method. The separation of the drug and its degradation products was achieved with the polymer-based PLRPs column (250 mm × 4.6 mm, 5 μm) in gradient elution mode. The mixture of 100 mM n-hexylamine and 100 mM acetic acid in water was used as buffer solution. Mobile phase A and mobile phase B were prepared by mixing the buffer and acetonitrile in the ratio of 90:10 (v/v) and 20:80 (v/v), respectively. Mobile phases were delivered in isocratic mode (2% B for 0–5 min) followed by gradient mode (2–85% B in 5–60 min). An Evaporative Light Scattering Detector (ELSD) was connected to the LC system to detect the responses of chromatographic separation. Further, the drug was subjected to stress studies for acidic, basic, oxidative, photolytic, and thermal degradations as per ICH guidelines and the drug was found to be labile in acid, base hydrolysis, and oxidation, while stable in neutral, thermal, and photolytic degradation conditions. The method provided linear responses over the concentration range of the LOQ to 0.30% for each impurity with respect to the analyte concentration of 12.5 mg/mL, and regression analysis showed a correlation coefficient value (r2) of more than 0.99 for all the impurities. The LOD and LOQ were found to be 1.4 μg/mL and 4.1 μg/mL, respectively, for fondaparinux. The developed ion-pair method was validated as per ICH guidelines with respect to accuracy, selectivity, precision, linearity, and robustness

Objective: The objective of current investigation was to study the degradation behavior of Ciprofloxacin and Tinidazole. The study was performed as per International Conference on Harmonization recommended stress condition. A novel stability-indicating reverse phase HPLC method was developed for the determination of Ciprofloxacin and Tinidazole purity in the presence of its impurities and forced degradation products. This method is also capable to separate placebo peaks as well in pharmaceutical dosage forms. The solid oral dosage form was subjected to the stress conditions such as oxidative, acid, base hydrolysis, heat and photolytic degradation. Materials and Methods: The method was developed using Waters symmetry shield, Reverse Phase (RP) C18, 250mm x 4.6mm, 5΅ as a stationary phase. The mobile phase containing a gradient mixture of solvent A and B. 10mM phosphate buffer, adjusted pH 3.0 with phosphoric acid was used as a buffer. Buffer pH 3.0 was used as solvent A and buffer pH 3.0: Acetonitrile in the ratio of 20: 80 v/v were used as solvent B. The eluted compounds were monitored 278 nm (Ciprofloxacin), 317 nm (Tinidazole). The run time was 50 minute. Results: In the precision study the % RSD for the result of Ciprofloxacin, Tinidazole and its impurities was below 10%. The method was linear with the correlation coefficient greater than 0.997. The percentage recoveries were calculated and observed from 93.0% to 106.7%.The peak purity of Ciprofloxacin, Tinidazole peak had not shown any flag, thus proved the stability-indicating power of the method. Conclusion: The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness.

The objective of current investigation was to study the degradation behaviour of eberconazole nitrate and mometasone furoate under different International Conference on harmonisation recommended stress condition using reverse phase high performance liquid chromatographic method and to establish validated stability-indicating high performance liquid chromatographic method to determine purity of eberconazole nitrate and mometasone furoate in presence of its impurities, forced degradation products and placebo in pharmaceutical dosage forms. The method was developed using Hypersil BDS, C18, 150Χ4.6 mm, 5 μ as stationary phase with mobile phase containing a gradient mixture of solvent A and B. 0.01 M phosphate buffer with 0.1% triethyl amine, adjusted pH 7.0 with phosphoric acid was used as buffer. Buffer pH 7.0 was used as solvent A and methanol:acetonitrile in 150:850 v/v ratios were used as solvent B. The eluted compounds were monitored at 240 nm. The run time was 50 min. The developed method was validated as per international conference on harmonization guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness.

A gradient reversed phase HPLC method was developed and validated for the analysis of related substances in zonisamide (1,2-benzisoxazole-3-methanesulfonamide), using a Waters Symmetry C8 (150*3.9 mm) column with a flow rate of 1.0 ml/min and detection at 280 nm. The mobile phase component A consisted of a mixture of 0.02 M aqueous potassium dihydrogen phosphate-acetonitrile-methanol (75:10:15 v/v/v), pH adjusted to 4.0 with orthophosphoric acid. The mobile phase component B consisted of a mixture of 0.02 M aqueous potassium dihydrogen phosphate-acetonitrile-methanol (15:40:45 v/v/v), pH 2.0 with orthophosphoric acid. The limit of detection and limit of quantitation were in the range of 0.001-0.007% and 0.0035-0.25% respectively with respect to sample concentration of 2 mg/ml. The method was linear in the range of LOQ level to 200% of specified limits for II-VIII (< 0.10%, r(2)= 0.9958-0.9999). The method is sensitive, specific, linear, accurate, precise and stability-indicating for the detection and quantitation of precursors (viz., 4-hydroxycoumarin, 1,2-benzisoxazole-3-acetic acid, 1,2-benzisoxazole-3-bromoacetic acid, 1,2-benzisoxazole-3-methylbromide, sodium 1,2-benzisoxazole-3-methanesulfonate), process impurities (viz., 2-hydroxyacetophenone oxime and 3,3,3-tribromomethyl-1,2-benzisoxazole) and drug degradation products formed under stress conditions.