Sodium Dihydrogen Phosphate Buffer Research Articles

A Novel Stress Indicating RP-HPLC Method Development and Validation for the Simultaneous Estimation of Velpatasvir and Sofosbuvir in Bulk and Its Tablet Dosage Form

Aim: The objective of the study was simplest, accurate, precise and robust reversed phase high performance liquid chromatographic (RP-HPLC) method was developed for the estimation of Velpatasvir (VEL) and Sofosbuvir (SOF) in the bulk and its tablet dosage form.
 Study Design: The Quantitative and Qualitative estimation and designed forced degradation study of Velpatasvir & Sofosbuvir by RP-HPLC.
 Place and Duration of Study: The study was carried at Santhiram College of Pharmacy and time taken 4 months.
 Method: The method was attained by used Waters( 5µm, C18 250 x 4.6 mm) column with mobile phase consists of 0.5 mM disodium hydrogen phosphate buffer pH adjusted to 6.5, with Orthophosphoric acid and Methanol in the ratio of 78:22 v/v, a flow rate of 1.0 mL/min and ultraviolet detection at 285 nm.
 Results: The method was validated as per ICH guidelines with different parameters, the mean retention times of VEL and SOF were found to be 2.8 & 4.7 min respectively. The resolution between VEL and SOF was found to be 10.66. The Correlation coefficients for calibration curves within the detection range of 32.5 - 97.5 and 125 - 375 µg/mL were 0.999 for VEL and SOF respectively. The LOD and LOQ for VEL and SOF were found to be 0.0068-0.029 µg/mL and 0.104-0.342 µg/mL respectively.
 Conclusion: The results were indicated that the developed method was used for the routine analysis of VEL & SOF combined form in bulk and its commercial formulation. To the best of our knowledge, there was no method of RP-HPLC for the determination of VEL alone or in combination with SOF molecule.

The efficacy of anti-VEGF antibody-modified liposomes loaded with paeonol in the prevention and treatment of hypertrophic scars

The aim of this study was to investigate the efficacy of anti-VEGF antibody-modified Paeonol liposome gels (PAE-BEV-lip gels) in the prevention and treatment of hypertrophic scars (HS). Systematic optimization of the encapsulation process of anti-VEGF antibody-modified Paeonol liposomes (PAE-BEV-lips) was performed using Box–Behnken design with the optimized parameters as follows: SPC concentration of 7.36 mg mL−1; SPC-Chol-PAE:pNP-PEG3000-DOPE:BVE-PEG3000-DOPE ratio of 14:5:4:0.28:0.05, w/w; the hydration temperature of 41 °C; stripping using pH 7.5 sodium dihydrogen phosphate buffer; and ultrasound for 3 min (ultrasound time 2 s, interval 3 s, power 300 W). Using these conditions, the encapsulation efficiency of PAE reached the peak level, i.e. 73.61 ± 2.36%. The PAE-BEV-lips displayed unimodal size-distribution with a mean diameter of (235.7 ± 4.67) nm and a zeta potential of –(5.13 ± 0.25) mV. The investigation of the retention effect PAE-BEV-lip gels revealed a slower transdermal delivery rate, a remarkable dermal retention effect, and superior bioavailability compared to PAE gels and PAE conventional liposome gels (PAE-lip gels). Meanwhile, PAE-BEV-lip gels exhibited definite effects on the prevention and treatment of HS of the rabbit ears. The PAE-BEV-lip gels group showed a lower scar proliferation rate, fewer and looser collagenous fibers and fibromyocytes, more regular chondrocytes, less calcified tissue and fewer inflammatory cells compared to other groups. At the same time, PAE-BEV-lip gels significantly reduced scar hyperplasia index (1.34 ± 0.51) and levels of VEGF, TGF-β1 and TNF-α (30.90 ± 3.57, 733.2 ± 43.19 and 66.76 ± 2.98 ng·L−1, respectively), compared to the model group (p < .01).

Simultaneous estimation of Cetrizine hydrochloride and Phenylephrine hydrochloride in tablet dosage form by RP-HPLC

A simple, economical, specific, accurate, precise and validated Reverse phase high performance liquid chromatography (RP-HPLC) method has been developed for the simultaneous estimation of Cetrizine hydrochloride and Phenylephrine hydrochloride in synthetic mixture and its combined dosage form. The chromatographic separation was achieved on C18 column (Intersil, 220 mm 4.6 mm i.d., 10 ?m particle size) at ambient temperature using disodium hydrogen phosphate (Na 2 HPO 4 ) buffer; pH was adjusted to 6.50 using ortho-phosphoric acid and a mobile phase of Methanol: Acetonitrile: Disodium hydrogen phosphate (80: 4: 19, v/v) at flow rate 2.0 ml/min. Quantification was achieved with UV detector at wavelength 270 nm. The retention time was found to be 1.2 0.04 min and 3.1 0.06 min for cetirizine HCl and phenylephrine HCl respectively. The calibration curves were linear with correlation coefficient 0.998 and 0.999 in the range of 10-50 ?g/ml for Cetrizine hydrochloride and Phenylephrine hydrochloride. The methods were validated in terms of linearity, precision, accuracy, LOD, LOQ and ruggedness according to ICH guideline.

Optimization and validation of RP-HPLC method for simultaneous estimation of palbociclib and letrozole

A simple, rapid, and robust RP-HPLC method have been developed and validated to measure palbociclib (PB) and letrozole (LT) at single wavelength (254 nm). A isocratic elution of samples performed on Intersil C8 (4.6 mm × 250 mm particle size 5 μm) column with mobile phase consisting 0.02 M sodium dihydrogen phosphate buffer (pH 5.5): acetonitrile: methanol (80:10:10 v/v/v) delivered at flow rate 1.0 mL min−1. A good linear response was achieved over the range of 5–50 μg mL−1. The LODs for PB and LT were found to be 0.098 and 0.0821 µg mL−1, while the LOQs for PB and LT were 0.381–0.315 µg mL−1, respectively. The method was quantitatively evaluated in terms of system suitability test, linearity, precision, accuracy (recovery) and robustness as per standard guidelines. The method is simple, convenient and suitable for the analysis of PB and LT in bulk drug.

VALIDATED CHIRAL RP-UFLC METHOD FOR THE QUANTIFICATION OF CHLORTHALIDONE IN BULK AND PHARMACEUTICAL DOSAGE FORM

Objective: Development and validation of new, simple and reliable enantioselective reverse phase ultra-fast liquid chromatography (RP-UFLC) method for quantification of chlorthalidone in bulk and pharmaceutical dosage form.Methods: In the present study, the isocratic RP-UFLC method was developed on Phenomenex® Lux cellulose 4 column (250×4.6 mm, 5µ) and di-sodium hydrogen phosphate buffer (pH 3.6): methanol (40:60 v/v) as mobile phase. Elute was monitored at 240 nm with a flow rate of 1 ml/min.Results: The described method provided linear correlation (R2=0.999) between the range of 2-10 µg/ml. Chlorthalidone enantiomers showed good resolution with a retention time (tR) of 5.75 min and 7.46 min respectively. The precision of the method revealed that relative standard deviation is within the acceptable limit. The percentage recovery of each chlorthalidone enantiomers was found to be 99.98% and 100.09% respectively. The method was validated in accordance with ICH harmonized tripartite guidelines, validation of analytical procedures: text and methodology Q2 (R1).Conclusion: An economical, accurate, sensitive and precise RP-UFLC method was developed and fully validated for quality control analysis of chlorthalidone in pharmaceutical dosage form.

Optimization and Validation for Simultaneous Estimation of Citicoline and Piracetam in bulk and tablet formulations using RP-HPLC method: Analytical quality by design approach

The present work describes a reversed phase high performance liquid chromatographic method for simultaneous estimation of Citicoline (CIT) and Piracetam (PIR) in bulk as well as tablet dosage forms. The estimation was carried out on a C18 column using mobile mixture of acetonitrile and 10 mM disodium hydrogen phosphate buffer in the ratio of 10: 90 (v/v) as a mobile phase. All analytes were detected by measuring the absorbance at 205 nm with flow rate of 1.0 ml/min. The total run time of the study was 16 min. for complete separation of both drugs. The elution was achieved at the retention times of 3.79 and 13.08 min for Citicoline, and Piracetam, respectively. The method was validated for accuracy, precision, linearity, specificity and sensitivity as per ICH norms. The calibration curves were found linear over the concentration ranges of 4–40μg/mL for Citicoline and 5–50μg/mL for Piracetam. From the validation study it was found that the method is specific, rapid, accurate and precise.

DEVELOPMENT AND VALIDATION OF STABILITY-INDICATING HPLC METHOD FOR DETERMINATION OF BOCEPREVIR

A simple and rapid stability indicating HPLC method for Boceprevir was successfully developed and was validated. This method is based on HPLC separation followed by UV detection at 215 nm. HPLC method was developed on a symmetry Thermo C18 (250 x 4.6 mm i.d, 5 μm) column (sr no. 0860953Q) with a mobile phase consisting of methanol : 10mM di-sodium hydrogen phosphate buffer(pH 2.5):triethylamine 90:10:0.05 % v/v/v, pumped at 1.0 ml min-1 flow rate. The pH of buffer was adjusted to 2.5 with ortho phosphoric acid. The column was maintained at ambient temperature. The eluted compound was detected by using PDA detector. Boceprevir eluted at 3.33± 0.2 min. Stress degradation study shows that sample degraded with acid and base hydrolysis, under oxidation, thermal and photolytic stress conditions. The method was validated in accordance with requirement of ICH guidelines.

Studies on the application of temperature-responsive ion exchange polymers with whey proteins

Several new types of temperature-responsive ion exchange resins of different polymer composition have been prepared by grafting the products from the co-polymerisation of N-phenylacrylamide, N-iso-propylacrylamide and acrylic acid derivatives onto cross-linked agarose. Analysis of the binding isotherms for these different resins obtained under batch adsorption conditions indicated that the resin based on N-iso-propylacrylamide containing 5% (w/w) N-phenylacrylamide and 5% (w/w) acrylic acid resulted in the highest adsorption capacity, Bmax, for the whey protein, bovine lactoferrin, e.g. 14mg bovine lactoferrin/mL resin at 4°C and 62mg bovine lactoferrin/mL resin at 40°C, respectively. Under dynamic loading conditions at 40°C, 94% of the loaded bovine lactoferrin on a normalised mg protein per mL resin basis was adsorbed by this new temperature-responsive ion-exchanger, and 76% was eluted by a single cycle temperature shift to 4°C without varying the composition of the 10mM sodium dihydrogen phosphate buffer, pH 6.5, or the flow rate. The binding characteristics of these different ion exchange resins with bovine lactoferrin were also compared to results obtained using other resins based on N-isopropylacrylamide but contained N-tert-butylacrylamide rather than N-phenylacrylamide, where the corresponding dynamic capture and release properties for bovine lactoferrin required different temperature conditions of 20°C and 50°C, respectively for optimal desorption/adsorption. The cationic protein, bovine lactoperoxidase, was also adsorbed and desorbed with these temperature-responsive resins under similar conditions of changing temperature, whereas the anionic protein, bovine β-lactoglobulin, was not adsorbed under this regime of temperature conditions but instead eluted in the flow-through.

Development and Validation of Liquid Chromatography Method for the Determination and Quantification of Impurities in Imiquimod

New stability indicating reverse phase high performance liquid chromatography (HPLC) method is developed for the determination of Imiquimod and its impurities. Separation is achieved on a C18 column (Inertsil-ODS3 4.6 × 250 mm, 5 µm) using gradient elution mode with mobile phase-A having disodium hydrogen phosphate buffer (10 mM) with 0.1% v/v triethyl amine and pH adjusted to 6.0 with ortho-phosphoric acid while mobile phase-B consist of an equal mixture of methanol and acetonitrile. The flow rate was optimized to 1.2 mL/min and column oven temperature 30°C. Detection was carried out at wavelength 226 nm. This developed method is then validated as per International Council for Harmonisation (ICH) guideline and found out to be linear, accurate, specific, selective, precise, and robust. The drug is also subjected to forced degradation using stress conditions of acid-base hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found out only in harsh condition of oxidative degradation where degradation impurity is also predicted. All degradation products were well separated. Test solution was found to be stable for 24 hrs. The method can be successfully applied for the determination of Imiquimod and its impurities in routine and stability samples.

Development and Validation of HPLC Method for Estimation of Pregabalin in Bulk &amp; Capsule Dosage Form

A simple, rapid, specific, precise and accurate HPLC method has been developed for the estimation of Pregabalin in bulk drugs and in capsule dosage forms. The mobile phase consisted of 80: 10: 10 (v/v/v) of Disodium Hydrogen Phosphate Buffer: Acetonitrile: Methanol. The flow rate is 1 ml/min. Chromatographic determination of Pregabalin was performed on Inertsil ODS -3V, C18 (250 X 4.6 mm Id, 5μm) column. The wavelength of detection is 210 nm. The injection volume is 20μL. The retention time of Pregabalin is 4.7 minutes. The developed method was validated in terms of specificity, accuracy, precision, linearity, solution stability, ruggedness, robustness and system suitability. The influence of Acid, Alkaline, Oxidative Stress, Photolytic stress, Thermal stress, and Humidity stress conditions on pregabalin was studied. Results indicated that Pregabalin is stable under the experimental conditions. The proposed method has been successfully used for the routine analysis of pregabalin in capsule dosage forms.

Chromatographic Methods for Simultaneous Determination of Moxifloxacin Hydrochloride and Difluprednate in Ophthalmic Dosage Form

Two simple, accurate, specific, and precise chromatographic methods, reversed phase high-performance liquid chromatography (RP-HPLC) and highperformance thin-layer chromatography (HPTLC), have been developed and validated for the determination of moxifloxacin hydrochloride and difluprednate in ophthalmic dosage form according to International Conference on Harmonization (ICH) guidelines. The separation of moxifloxacin hydrochloride and difluprednate in HPLC was performed on reverse phase (C18, 5 μm, 250 × 4.6 mm) column using isocratic condition, with acetonitrile, 5 mM disodium hydrogen phosphate buffer adjusted to pH 5, and methanol (50:25:25, v/v/v) as mobile phase. The flow rate for analysis was 1.0 mL min−1, and the selected chromatographic conditions effectively separated moxifloxacin hydrochloride and difluprednate with retention time of 3.6 and 6.6 min, respectively, at a detection wavelength of 254 nm. Chromatographic development in HPTLC was performed on precoated silica gel 60F254 aluminium pla...

Development and Validation of a Specific RP-HPLC Method for the Estimation of γ-Aminobutyric Acid in Rat Brain Tissue Samples Using Benzoyl Chloride Derivatization and PDA Detection

A new, rapid, and specific reversed phase high-performance liquid chromatographic (RP-HPLC) method involving precolumn derivatization with benzoyl chloride was developed and validated for the estimation of γ-aminobutyric acid (GABA) in rat brain tissue preparations. The derivatization product of GABA was identified by melting point, infrared, and proton nuclear magnetic resonance (1H NMR) spectroscopy to be n-benzoyl GABA. Various parameters which influenced derivatization and elusion were optimized. The chromatographic system consisted of C-18 column with ultraviolet (UV)—photodiode array detection ranging from 210 to 400 nm. Elution with an isocratic mobile phase consisting of 0.025 M disodium hydrogen phosphate buffer—methanol (65:35, v/v; pH 6) at a flow rate of 1 mL min−1 yielded sharp and specific peak of n-benzoyl GABA within 7 min. The method was validated with respect to the linearity, accuracy, precision, sensitivity, selectivity, and stability, wherein the benzoyl derivative of GABA showed stab...

Development of a test strip for rapid detection of lactoperoxidase in raw milk.

Traditional methods for detecting lactoperoxidase (LP) are complex and time-consuming, so a test strip was made based on the enzymatic reaction principle to enable quick and convenient detection of LP in raw milk. In this study 0.1 mol/L citric acid (CA)/0.2 mol/L disodium hydrogen phosphate (NaP) buffer solution (pH 5.0), 22 mmol/L 3,3',5,5'-tetramethylbenzidine (TMB), 0.6 mmol/L hydrogen peroxide (H2O2), and 0.5% Tween-20 or 0.3% cetyltrimethyl ammonium bromide (CTAB) were optimal for preparing a quick, sensitive, and accurate LP test strip. The coefficient of variation (CV) of the estimated LP concentrations ranged from 2.47% to 6.72% and the minimum LP concentration detected by the test strip was 1-2 mg/L. Estimates of active LP in sixteen raw milk samples obtained using the test strip or the TMB method showed a good correlation (r=0.9776). So the test strip provides a quick, convenient, and accurate method for detecting the LP concentration of raw milk.

Synthesis and characterization of surface-functionalized paramagnetic nanoparticles and their application to immobilization of α-acetolactate decarboxylase

In this paper, a facile paramagnetic Fe3O4@SiO2NH2 nanoparticles (PMN Fe3O4@SiO2NH2 NPs) have been successfully synthesized and characterized, which were applied to α-acetolactate decarboxylase (α-ALDC) immobilization using 1, 1′-carbonyldiimidazole (CDI) as the covalent reagent. The synthesized nanoparticles exhibited satisfactory paramagnetic under magnetic field, high single-crystalline and abundant amino groups on the surface. The α-ALDC loading capacity onto nanoparticles was 48.70±1.25μg/mg carrier and the activity of retained α-ALDC remained 69.39±1.16% in comparison with free α-ALDC. Enzyme kinetics analysis showed that immobilized α-ALDC had lower affinity to its substrate than that of free α-ALDC based on higher Km and little lower Vmax of immobilized α-ALDC. After storage at 4°C in disodium hydrogen phosphate and citric acid (DHPCA) buffer (20mM, pH 6) for 14 days, immobilized α-ALDC retained 65.35% of its initial activity, while the activity of free α-ALDC only kept 39.22% in the same conditions. After 5 times re-use, immobilized α-ALDC still retained 31.03% of its initial activity for preventing diacetyl production.

HPTLC and RP-HPLC methods for simultaneous determination of Paracetamol and Pamabrom in presence of their potential impurities

Two chromatgraphic methods were developed for determination of Paracetamol (PCM) and Pamabrom (PAM) in presence of P-aminophenol (PAP) and Theophylline (THEO) as potential impurities of both drugs respectively. First method is HPTLC which depends on separation and quantitation of the studied drugs on aluminum plates pre-coated with silica gel 60 F254 as a stationary phase using chloroform:methanol:ethyl acetate:glacial acetic acid (8:0.8:0.6:0.2, v/v/v/v) as mobile phase followed by densitometric measurement of the bands at 254nm. Second method is RP-HPLC which comprises separation of the studied drugs on a Phenomenex C8 column by gradient elution using mobile phase consisting of sodium dihydrogen phosphate buffer (0.05M): methanol:acetonitrile (85:10:5, v/v/v) at a flow rate of 1mL/min for first 7.5min and (70:20:10, v/v/v) at a flow rate of 1.5mL/min for the next 5min. The proposed methods were successfully applied for determination of the potential impurities of PCM and PAM after resolving them from the pure drugs. The developed methods have been validated and proved to meet the requirements delineated by ICH guidelines with respect to linearity, accuracy, precision, specificity and robustness. The validated methods were successfully applied for determination of the studied drugs in their pharmaceutical formulation. The results were statistically compared to those obtained by the reported RP-HPLC method where no significant difference was found; indicating the ability of proposed methods to be used for routine quality control analysis of these drugs.

Development and Validation of a Stability-Indicating HPLC Method for the Determination of the Impurities in Cabazitaxel

A novel stability-indicating high-performance liquid chromatographic (HPLC) method has been developed and validated for the analysis of the impurities A–G in cabazitaxel. Chromatographic separation was achieved on a Welch Xtimate™ C18 (250 × 4.6 mm; 5 μm) column, using the mixture of 0.02 mol L−1 sodium dihydrogen phosphate buffer pH 3.0 (pH value was adjusted with phosphoric acid) and acetonitrile as mobile phase by gradient elution with a flow rate of 1.0 mL min−1, and UV detection was performed at 230 nm. The column temperature was maintained at 40 °C by column oven. The method was validated according to the International Conference on Harmonization (ICH) guidelines. Linearity (r > 0.9990) was observed over the concentration ranges of 25.0–1500.0, 31.5–1518.0, 74.9–1796.8, 65.6–1573.2, 59.4–1425.6, 22.2–1332.0, 1.3–1570.8, 30.8–1476.0 ng mL−1 of cabazitaxel and its impurities A–G, respectively. The RSD value of the recovery for each impurity was <5.0 % (n = 9). The method was found simple and rapid with good specificity and robustness, which can be suitable for the determination of the impurities in cabazitaxel.

Optimization and validation of an HPLC-photodiode array detector method for determination of organic acids in vinegar.

A novel isocratic RP-HPLC method with UV photodiode array detection for the determination of seven organic acids in vinegar samples was developed and optimized. Samples were analyzed on a C18 (150 × 4.6 mm id, 5 μm) analytical column. Methanol-0.010 M sodium dihydrogen phosphate buffer adjusted with H3PO4 to pH 2.80 (2 + 98, v/v), was used as the mobile phase. The column oven temperature was optimized at 23.0°C, the flow rate was 0.80 mL/min, and the detection wavelength was 210 nm. Matrix-matched calibration curves were prepared for all analytes, and the correlation coefficients were greater than 0.99. LOD and LOQ ranged from 0.10 to 10.0 and 0.30 to 30.0 μg/mL, respectively. The results for interday and intraday precision and accuracy fell within the ranges specified. Vinegar samples were quantified by the standard addition method. The main advantages of this method are its selectivity, which is one of the main weaknesses of most methods when determining organic acids in complex matrixes, and its simplicity since little sample preparation is needed. Moreover, it is safe and inexpensive with low organic solvent usage.

Simultaneous determination of camptothecin and 10-hydroxycamptothecine in the Camptotheca acuminate, its medicinal preparation and in rat plasma by liquid chromatography with fluorescence detection.

Camptotheca acuminata Decne is an important medicinal plant that contains various cytotoxic alkaloids, such as camptothecine (CPT) and 10-hydroxycamptothecine (HCPT). A rapid and sensitive liquid chromatography with fluorescence detection (LC-FLD) method for the quantification of CPT and HCPT is described. The separation was carried out on a DL-Cl8 column (4.6 × 150 mm, 5 µm), with the mobile phase of acetonitrile-sodium dihydrogen phosphate buffer (10 mm) using an gradient elution at the flow rate of 0.6 mL/min. The LC-FLD method was validated for linearity, sensitivity, accuracy and precision, and then used to determine the content of the above components. The lower detection limits of CPT and HCPT were 0.4 and 0.1 ng/mL, respectively. The precision was <1.58% and the mean recovery of the analytes was 96.0-98.6%. The LC-FLD method was successfully applied to determine CPT and HCPT in real samples including C. acuminate, HCPT injection and rat plasma.

Investigation of the enantiomerization barriers of the phthalimidone derivatives EM12 and lenalidomide by dynamic electrokinetic chromatography.

The phthalimidone derivatives EM12 and lenalidomide, which are both structurally related to thalidomide, are highly interesting drugs and very recently lenalidomide attracted great attention as an antitumor and immune-modulating drug in the therapy for multiple myeloma. EM12 and lenalidomide are chiral, and the stereogenic carbon C-3 in the piperidine-2,6-dione moiety of these phthalimidone derivatives is prone to interconversion due to keto-enol tautomerization. The knowledge of the enantiomerization barrier is mandatory for pharmacokinetic studies and to develop a tailored therapy using the enantiopure or racemic drug. Here, we used dynamic EKC in combination with direct-calculation methods to determine the enantiomerization barriers of EM12 and lenalidomide. The separations of the enantiomers of EM12 and lenalidomide were performed in 50 mM aqueous disodium hydrogen phosphate buffer at pH 8 and 50 mM aqueous sodium tetraborate buffer at pH 9.3, respectively, using 20 mg/mL heptakis-(2,3-diacetyl-6-sulfato)-β-CD as a chiral additive. Enantiomerization of the compounds during the electrokinetic chromatographic separation resulted in pronounced plateau formation between the well-separated enantiomers. Peak form analysis of the experimentally obtained interconversion profiles yielded the enantiomerization rate constants k1 of EM12 and lenalidomide as well as the kinetic activation parameters ΔG(‡), ΔH(‡‡), and ΔS(‡) of enantiomerization by the evaluation of temperature-dependent measurements. The enantiomerization barrier ΔG(‡) was determined to be 98.3 ± 1.0 kJ/mol; the activation parameters ΔH(‡) = 46.1 ± 2.4 kJ/mol and ΔS(‡) = -170 ± 61 J/(K·mol) for EM12 and ΔG(‡) = 91.5 ± 1.0 kJ/mol, ΔH(‡) = 62.4 ± 5.4 kJ/mol, and ΔS(‡) = -98 ± 7 J/(K·mol) for lenalidomide. These findings were corroborated by density functional theory calculations at the B3LYP/3-21G level of theory of the ground state and intermediates considering an enantiomerization pathway via a keto-enol tautomerism.

Determination of Buspirone HCl in Commercial Dosage Forms by Extractive Spectrophotometric Method and Comparison by HPLC Method

An extractive spectrophotometric method has been developed for the determination of buspirone HCl in tablets. It was based on the ion-pair complex formation between buspirone and bromothymol blue in presence of disodium hydrogen phosphate and citric acid buffer solution of pH 4.0 which is extractable in chloroform. The extracted complex showed maximum absorbance at 412 nm. Beer’s law was obeyed in the concentration range of 1.25-30 μg ml-1. Various factors affecting the reaction conditions were carefully studied and optimized. Validation parameters based on the guidelines of International Conference on Harmonisation, USA were followed. Effect of common excipients used as additives has been tested and the tolerance limit was calculated for the determination of buspirone HCl. Limits of detection and quantitation were 0.165 and 0.499 g ml-1, respectively. Proposed method has been successfully applied for the determination of buspirone HCl in pharmaceutical formulations. High performance liquid chromatographic method was employed using 250 mm × 4.6 mm i.d., 5-m particle, reversed phase C18 column with 70:30 (v/v) methanol-0.01M NaH2PO4 buffer as a mobile phase at a flow rate of 0.8 ml min-1 and UV detection at 240 nm for best separation of buspirone. Results obtained by the proposed method were statistically compared with the HPLC reference method using t- and F- values and found no significant difference between the two methods. The proposed method can be used as an alternate method for routine quality control analysis of buspirone HCl in pharmaceutical formulations.