A Stability-Indicating LC Method for Candesartan Cilexetil

An isocratic reversed-phase liquid chromatographic method has been developed for quantitative determination of candesartan cilexetil, used to treat hypertension, in the bulk drug and in pharmaceutical dosage forms. The method is also applicable to analysis of related substances. Chromatographic separation was achieved on a 250 mm × 4.6 mm, 5 μm particle, CN column with a 50:50 (v/v) mixture of phosphate buffer, pH 3.0, and acetonitrile as mobile phase. The flow rate was 1.0 mL min⁻¹ and the detection wavelength was 210 nm. Resolution of candesartan cilexetil and six potential impurities was greater than 2.0 for all pairs of compounds. The drug was subjected to hydrolytic, oxidative, photolytic, and thermal stress and substantial degradation occurred in alkaline and acidic media and under oxidative and hydrolytic stress conditions. The major product obtained as a result of basic hydrolysis was different from that produced by acid hydrolysis and aqueous hydrolysis. The stress samples were assayed against a reference standard and the mass balance was found to be close to 99.6%. The method was validated for linearity, accuracy, precision, and robustness.     

Development of a New Analytical Method for Determination of Related Components in Nateglinide

An isocratic reverse phase liquid chromatographic (RP-LC) assay method has been developed for the quantitative determination of nateglinide and its related components namely imp-1 and imp-2 in bulk drug and in pharmaceutical dosage form, used for the treatment of type II diabetes mellitus. The developed method is stability indicating and also can be used for stability testing. The chromatographic separation was achieved on C-8, 150 × 4.6 mm, 3.5 μm stationary phase. The LC method employs solution A as mobile phase. Solution A contains a mixture of phosphate buffer pH 3.0: acetonitrile (50:50 v/v). The flow rate was 1.0 mL min⁻¹ and the detection wavelength was 210 nm. In the developed LC method the resolution between nateglinide and its potential impurities namely imp-1 and imp-2 was found to be greater than 5.0. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in acid medium, alkaline medium and oxidative stress conditions. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.2%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.     

A Stability-Indicating Assay of Brimonidine Tartrate Ophthalmic Solution and Stress Testing Using HILIC

A stability-indicating hydrophilic interaction liquid chromatography (HILIC) method has been developed and validated for the quantitative determination of Brimonidine tartrate (BT) formulated as an ophthalmic solution. Isocratic separation was achieved using an acetonitrile-buffer mixture (92:8, v/v) at pH 7.1 on an unmodified silica column (250 × 4.6 mm, 5 μm). The drug was subjected to oxidative, hydrolytic, photolytic and thermal stress conditions and complete separation was achieved for the parent compound and degradation products. The influence of acetonitrile, pH and ionic strength of the buffer was studied. Linearity range and recoveries for BT were 100–400 μg mL^?1 and 100.12%, respectively. The method was validated for BT and indicated that the method was sufficiently sensitive with a limit of detection at 0.005 μg mL^?1 and a limit of quantitation at 0.02 μg mL^?1, respectively.     

Analysis of duloxetine hydrochloride and its related compounds in pharmaceutical dosage forms and in vitro dissolution studies by stability indicating UPLC

A reproducible gradient reversed-phase ultra-performance liquid chromatographic method is developed for quantitative determination of duloxetine hydrochloride in pharmaceutical dosage forms. The method is also applicable for analysis of related substances and for study of in vitro dissolution profiles. Chromatographic separation is achieved on a 50 mm × 4.6 mm, 1.8 μm C-18 column. Mobile phase A contains a mixture of 0.01 M KH(2)PO(4) (pH 4.0) buffer, tetrahydro furan, and methanol in the ratio 67:23:10 (v/v/v), respectively, and mobile phase B contains a mixture of 0.01 M KH(2)PO(4), (pH 4.0) buffer, and acetonitrile in the ratio 60:40 (v/v), respectively. The flow rate is 0.6 mL/min, and the detection wavelength is monitored at 236 nm. Resolution of duloxetine hydrochloride and three potential impurities is greater than 2.0 for all pairs of components. The drug was subjected to ICH prescribed hydrolytic, oxidative, photolytic, and thermal stress conditions. Method is validated for linearity, specificity, accuracy, precision, ruggedness, and robustness.     

Development of an HPLC Assay Method for Lenalidomide

Chromatographic separation of lenalidomide and its impurities was achieved on an Inertsil ODS-3 V column using a mobile phase consisting of a mixture of buffer, acetonitrile and methanol in the ratio 80:8:12 v/v. Degradation studies were performed on bulk samples of lenalidomide subjected to 0.5 N hydrochloric acid, 0.5 N sodium hydroxide, 10% v/v hydrogen peroxide, heating to 60 °C and UV light at 254 nm. Degradation was observed only under base hydrolysis conditions. The developed LC method gave a mass balance close to 99.5%, proving it to be suitable for stability studies and was validated with respect to linearity, accuracy, precision and robustness.     

Stability-Indicating LC Determination of a New Antihypertensive,Olmesartan Medoxomil in Tablets

A stability-indicating liquid chromatographic method was developed and validated for quantitative determination of olmesartan medoxomil (OLM) in coated tablets in the presence of degradation products generated under stress conditions. An isocratic LC separation was performed using a Phenomenex RP-18 column using a mobile phase consisting of water:triethylamine:acetonitrile (60:0.3:40 v/v/v, pH adjusted to 6.3 with phosphoric acid). The flow rate was 1.2 mL min⁻¹ and the detection was achieved with a photodiode array detector set at 257 nm. The response was linear over a range of 10.0 to 30.0 μg mL⁻¹ (r = 0.9999). The specificity and stability-indicating capability of the method was verified subjecting the reference substance and drug product to hydrolytic, oxidative, photolytic, and thermal stress conditions. The method showed a good and consistent recovery (100.2%) with low intra- and inter-day relative standard deviation (RSD) (≤1.0%). A considerable degradation occurred in all stress conditions and the degradation product was well resolved from the main peak. There was no interference of the excipients in the determination of the active pharmaceutical ingredient. Thus, the proposed method was found to be stability-indicating and can be used for routine analysis for quantitative determination of OLM in coated tablets without the interference of major degradation products.

     

Stress Degradation Studies on Aripiprazole and Development of a Validated Stability Indicating LC Method

The present paper describes the development of a stability indicating reversed phase column liquid chromatographic method for aripiprazole in the presence of its impurities and degradation products generated from forced decomposition studies. The drug substance was subjected to stress conditions of aqueous hydrolysis, oxidative, photolytic and thermal stress degradation. The degradation of aripiprazole was observed under acid hydrolysis and peroxide. The drug was found to be stable to other stress conditions attempted. Successful separation of the drug from the synthetic impurities and degradation products formed under stress conditions was achieved on an Inertsil phenyl column using a mixture of 0.2% trifluoroacetic acid and acetonitrile (55:45, v/v). The developed LC method was validated with respect to linearity, accuracy, precision, specificity and robustness. The assay method was found linear in the range of 25–200 μg mL^?1 with a correlation coefficient of 0.9999 and the linearity of the impurities were established from LOQ to 0.3%. Recoveries of the assay and impurities were found between 97.2 and 104.6%. The developed LC method for the related substances and assay determination of aripiprazole can be used to evaluate the quality of regular production samples. It can also be used to test the stability samples of aripiprazole. To the best of our knowledge, the validated stability indicating LC method which separates all the impurities disclosed in this investigation was not published elsewhere.     

Stability-Indicating LC Method for the Determination of Olmesartan in Bulk Drug and in Pharmaceutical Dosage Form

A novel stability-indicating LC assay method was developed and validated for quantitative determination of olmesartan in bulk drugs and in pharmaceutical dosage form in the presence of degradation products generated from forced degradation studies. An isocratic, reversed phase LC method was developed to separate the drug from the degradation products, using an Ace5-C18 (250 mm × 4.6 mm, 5 μm) column, and 50 mM ammonium acetate (pH-5.5 by acetic acid) and acetonitrile (70:30 v/v) as a mobile phase. The detection was carried out at the wavelength of 235 nm. The olmesartan was subjected to stress conditions of hydrolysis (acid, base), oxidation, photolysis and thermal degradation. Degradation was observed for olmesartan in acid, base and in 30% H₂O₂ conditions. The drug was found to be stable in the other stress conditions attempted. The degradation products were well resolved from the main peak. The percentage recovery of olmesartan ranged from (99.89 to 100.95%) in pharmaceutical dosage form. The developed method was validated with respect to linearity, accuracy (recovery), precision, specificity and robustness. The forced degradation studies prove the stability-indicating power of the method.

     

Development and Validation of a Stability Indicating LC Method for the Determination of Faropenem in Pharmaceutical Formulations

A simple, selective and sensitive stability indicating LC method has been developed and validated for the determination of faropenem in bulk drug and pharmaceutical formulations in the presence of degradation products. The separation was achieved by using an isocratic mobile phase mixture of acetate buffer of pH 3.5 and methanol (65:35, v/v) and 250 mm × 4.6 mm I.D., 5 μm particle size SGE make Wakosil C-18 AR column at flow rate of 1.0 mL min^?1 with detection at 305 nm. The retention time of faropenem is 6.63 min and was linear in the range of 5–75 μg mL^?1 (r = 0.9999). The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation and was found to be unstable in all the stress conditions. The proposed method was successfully employed for quantification of faropenem in bulk drug and its pharmaceutical formulations.     

Stability-Indicating LC Determination of Nitazoxanide in Bulk Drug and in Pharmaceutical Dosage Form

A novel stability-indicating high-performance liquid chromatographic assay method was developed and validated for quantitative determination of nitazoxanide in bulk drugs and in pharmaceutical dosage form in the presence of degradation products generated from forced decomposition studies. An isocratic, reversed phase LC method was developed to separate the drug from the degradation products, using an Ace5- C18 (250 mm × 4.6 mm, 5 μm) column, and 50 mM ammonium acetate (pH 5.5 by acetic acid) and acetonitrile (55:45 v/v) as a mobile phase. The detection was carried out at a wavelength of 240 nm. The nitazoxanide was subjected to stress conditions of hydrolysis (acid, base), oxidation, photolysis and thermal degradation. Degradation was observed for nitazoxanide in base, acid and in 30% H₂O₂ conditions. The drug was found to be stable in the other stress conditions attempted. The degradation products were well resolved from the main peak. The percentage recovery of nitazoxanide was from (100.55 to 101.25%) in the pharmaceutical dosage form. The developed method was validated with respect to linearity, accuracy (recovery), precision, system suitability, specificity and robustness. The forced degradation studies prove the stability indicating power of the method.     

Identification and structural characterization of major degradation products of tapentadol by using liquid chromatography–tandem mass spectrometry

Tapentadol, a centrally acting analgesic was subjected to hydrolysis (acidic, alkaline, and neutral), oxidation, photolysis, humidity, and thermal stress conditions as per International Conference on Harmonization prescribed guidelines. Tapentadol was found susceptible to oxidative stress that produced two major degradation products DP-I and DP-II. However, it was stable to hydrolysis, photolysis, and thermal stress conditions. A simple, sensitive, and accurate high-performance liquid chromatography stability-indicating assay method (liquid chromatography–mass spectrometer compatible) was developed and validated for identification and characterization of stressed degradation products of Tapentadol. The chromatographic separation of the drug and its degradation products were achieved on Inertsil ODS, C18 (250 × 4.6 mm, i.d., 5 µm) column using a 12.5 mM aqueous ammonium acetate buffer (with 0.2% triethyl amine and final pH of buffer was adjusted to 3.60 with glacial acetic acid): acetonitrile (75:25, v/v) as a mobile phase. The degradation products were characterized by liquid chromatography mass spectrometry and subsequently its fragmentation pathway as well as plausible mechanism for generation of degradation products was also proposed. The stability indicating high-performance liquid chromatographic method was validated with respect to linearity, precision, and accuracy.     

LC Method for the Determination of the Stability of Levetiracetam Drug Substance under Stressing Conditions

Levetiracetam is used in combination with other medications to treat certain types of seizures in people with epilepsy. Levetiracetam is in a class of medications called anticonvulsants and it works by decreasing abnormal excitement in the brain. A chromatographic separation was achieved on a YMC pack ODS AQ, 250 mm × 4.6 mm, 5 μm column using diluted phosphoric acid and acetonitrile in the ratio 85:15 v/v. Forced degradation studies were performed on the levetiracetam drug substance. The drug substance was degraded to Imp-B during acid and base hydrolysis. When the stress samples were assayed, the mass balance was matching. The sample solution and mobile phase was found to be stable up to 48 h at 25 °C. The developed method was validated with respect to linearity, accuracy, precision and robustness.     

Stability-Indicating LC Determination of a New Antihypertensive, Olmesartan Medoxomil in Tablets

A stability-indicating liquid chromatographic method was developed and validated for quantitative determination of olmesartan medoxomil (OLM) in coated tablets in the presence of degradation products generated under stress conditions. An isocratic LC separation was performed using a Phenomenex RP-18 column using a mobile phase consisting of water:triethylamine:acetonitrile (60:0.3:40 v/v/v, pH adjusted to 6.3 with phosphoric acid). The flow rate was 1.2 mL min^?1 and the detection was achieved with a photodiode array detector set at 257 nm. The response was linear over a range of 10.0 to 30.0 μg mL^?1 (r = 0.9999). The specificity and stability-indicating capability of the method was verified subjecting the reference substance and drug product to hydrolytic, oxidative, photolytic, and thermal stress conditions. The method showed a good and consistent recovery (100.2%) with low intra- and inter-day relative standard deviation (RSD) (≤1.0%). A considerable degradation occurred in all stress conditions and the degradation product was well resolved from the main peak. There was no interference of the excipients in the determination of the active pharmaceutical ingredient. Thus, the proposed method was found to be stability-indicating and can be used for routine analysis for quantitative determination of OLM in coated tablets without the interference of major degradation products.     

Study of the Degradation Kinetics of Carvedilol by Use of a Validated Stability-Indicating LC Method

The objectives of this investigation were to establish a validated stability-indicating LC method for assay of carvedilol and to study the degradation behaviour of the drug under different ICH-recommended stress conditions. Chromatographic separation was achieved on a C₁₈ column with 55:45 (%, v/v) acetonitrile–0.02 m phosphate buffer, pH 3.5, as mobile phase at a flow rate of 1.0 mL min^?1; detection was by UV absorbance at 242 nm. The method was validated for linearity, precision, accuracy, robustness, specificity, and sensitivity, with the bulk drug. The drug was subjected to forced degradation and peaks of all the degradation products were well resolved from that of the pure drug, with significantly different retention times, which indicates the specificity and stability-indicating properties of the method. First-order degradation kinetics of carvedilol were observed under acidic and alkaline conditions. When the utility of the method was verified by analysis of the drug in marketed tablets and a nano-emulsion formulation, the assay was found to be 98.60–99.61 and 99.52–99.87, respectively. These results indicate the method can be successfully used for routine analysis of carvedilol in the bulk drug and in pharmaceutical dosage forms.     

Development and validation of stability indicating analytical method for Ilaprazole

The objective of the present study was to develop and validate a rapid and simple stability indicating analytical method for estimating Ilaprazole. Ilaprazole was subjected to different stress conditions prescribed by International Conference on Harmonization (ICH) such as hydrolysis, oxidation, photolytic and dry heat degradation conditions. The drug was very susceptible to degradation under hydrolysis and photolytic conditions, less susceptible to oxidation and stable under dry heat degradation condition. An acceptable separation of drug and its degradants was achieved by using a C-18 column and mobile phase composed of ammonium acetate buffer (pH 3.2)—acetonitrile (55: 45, v/v). Flow rate was 1 mL/min and detection wavelength was set at 303 nm. Retention time of drug was found to be 6.6 min and analysis can be completed within 10 min. The method was validated with respect to linearity, precision, accuracy, robustness, LOD and LOQ as per ICH. The method was linear (R² = 0.996) in the range of 2.5–250 μg/mL. The recovery was in the range from 99.2–100.2%.     

Preparation of Fritless Packed Silica Columns for Capillary Electrochromatography

Fritless packed silica gel columns were prepared using sol‐gel technology. A part of a 75 μm i.d. fused silica capillary was filled with a mixture of tetramethoxysilane and poly(ethylene glycol). After gelling at 40°C and heating at 300°C, the resultant silica gel was derivatized with dimethyloctadecylchlorosilane. A scanning electron micrograph of a cross‐section of the capillary column showed that the gel took the form of a spherical particle aggregate and adhered to the column inner wall. The column performance was evaluated for electrochromatography using acetonitrile–50 mM HEPES buffer (pH 6.6) (60/40 or 40/60, v/v) as the mobile phase. An electroosmotic flow of 1.0 mm/s was generated with (60/40, v/v) acetonitrile/HEPES buffer at a field strength of 546 V/cm. Using a sol‐gel‐derived packed column at an electroosmotic flow of 0.5 mm/s, efficiencies of up to 1.1×10⁵ plates/m were obtained for retained solutes.     

A Validated Stability Indicating RP-LC Method for Nitazoxanide, a New Antiparasitic Compound

The present paper describes stability indicating reverse phase high-performance liquid chromatography (RP-HPLC) assay method for nitazoxanide in bulk drugs. The developed method is also applicable for the related substances determination in bulk drug. The drug substance was subjected to stress conditions of hydrolysis, photolysis and thermal degradation. The considerable degradation of nitazoxanide was observed under base and peroxide hydrolysis. The drug was found to be stable in other stress conditions attempted. The chromatographic separation of the drug was achieved on reversed-phase C-18 column. Eluents were monitored on photo-diode array detector at a wavelength of 240 nm. The mobile phase was aqueous 0.005 M tetra butyl ammonium hydrogen sulphate and acetonitrile (45:55, v/v). In the developed HPLC method, resolution between nitazoxanide and its potential impurities, namely Imp-A (5-nitro-1,3-thiazol-2-amine), Imp-B (N-(5-nitro-1,3-thiazol-2-yl) acetamide) and Imp-C (2-{[(5-nitro-1,3-thiazol-2-yl) amino] carbonyl} phenyl 2-(acetyloxy) benzoate) was found greater than three. The developed RP-HPLC method was validated with respect to response function, accuracy, precision, specificity, stability of analytical solutions and robustness. Also to determine related substances and assay determination of nitazoxanide that can be used to evaluate the quality of regular production samples. The developed method can also be conveniently used for the assay determination of nitazoxanide in pharmaceutical formulations.     

Characterization of forced degradation products of pazopanib hydrochloride by UHPLC‐Q‐TOF/MS and in silico toxicity prediction

Pazopanib (PZ), an anti‐cancer drug, was subjected to forced degradation under hydrolytic (acid, base and neutral), oxidative, photolytic and thermal stress conditions as per International Conference on Harmonization guidelines. A selective stability indicating validated method was developed using a Waters Acquity UPLC HSS T3 (100 × 2.1 mm, 1.7 µm) column in gradient mode with ammonium acetate buffer (10 m m , pH 5.0) and acetonitrile. PZ was found to degrade only in photolytic conditions to produce six transformation products (TPs). All the TPs were identified and characterized by liquid chromatography/atmospheric pressure chemical ionization–quadrupole‐time of flight mass spectrometry experiments in combination with accurate mass measurements. Plausible mechanisms have been proposed for the formation of TPs. In silico toxicity was predicted using TOPKAT and DEREK softwares for all the TPs. The TP, N4‐(2,3‐dimethyl‐2H‐indazol‐6‐yl)‐N4‐methylpyrimidine‐2,4‐diamine, was found to be genotoxic, whereas all other TPs with sulfonamide moiety were hepatotoxic. The data reported here are expected to be of significance as this study foresees the formation of one potential genotoxic and five hepatotoxic degradation/transformation products. Copyright © 2015 John Wiley & Sons, Ltd.     

Chromatographic methods development,validation and degradation characterization of the antithyroid drug Carbimazole

The current paper reports the development and validation of stability‐indicating HPLC and HPTLC methods for the separation and quantification of main impurity and degradation product of Carbimazole. The structures of the degradation products formed under stress degradation conditions, including hydrolytic and oxidative, photolytic and thermal conditions, were characterized and confirmed by MS and IR analyses. Based on the characterization data, the obtained degradation product from hydrolytic conditions was found to be methimazole—impurity A of Carbimazole as reported by the British Pharmacopeia and the European Pharmacopeia. A stability‐indicating HPLC method was carried out using a Zorbax Eclipse Plus CN column (150 × 4.6 mm i.d, 5 μm particle size) and a mobile phase composed of acetonitrile–0.05 m KH₂PO₄ (20: 80, v/v) in isocratic elution, at a flow rate of 1 mL/min. The method was proved to be sensitive for the determination down to 0.5% of Carbimazole impurity A. Additionally, a stability‐indicating chromatographic HPTLC method was achieved using cyclohexane–ethanol (9:1, v/v) as a developing system on HPTLC plates F₂₅₄ with UV detection at 225 nm. The proposed HPLC and HPTLC methods were successfully applied to Carbimazole^® tablets with mean percentage recoveries of 100.12 and 99.73%, respectively.     

A Stability-Indicating LC Method for Assay of Topotecan Hydrochloride

This paper describes the development of a stability-indicating high-performance liquid chromatographic (HPLC) method for quantitative determination of topotecan hydrochloride, a semi-synthetic derivative of camptothecin and anti-tumor drug with topoisomerase I-inhibitory activity. Chromatographic separation was achieved on a C₁₈ column with a mixture of phosphate buffer and acetonitrile as mobile phase. The method was validated for linearity, accuracy, precision, and robustness. Forced degradation studies were performed by treating bulk samples of topotecan hydrochloride with acid (0.5 M hydrochloric acid), base (0.5 M sodium hydroxide), oxidizing agent (10% v/v hydrogen peroxide), heat (60 °C), and UV light (254 nm).