Development and validation of a micellar high-performance liquid chromatographic method for determination of risedronate in raw material and in a pharmaceutical formulation: application to stability studies

A micellar HPLC method was developed for analysis of the antiosteoporosis drug risedronate. The analysis was carried out using a 250 x 4.6 mm id, 5 microm particle size C18 Waters Symmetry column. The mobile phase consisted of 0.02 M sodium dodecyl sulfate + 0.3% triethylamine + 10% n-propanol, prepared in 0.02 M orthophosphoric acid. The pH of the mobile phase was adjusted to pH 6.0, and it was pumped at a flow rate of 0.7 mL/min with UV detection at 262 nm. The method showed good linearity in the range of 2-80 microg/mL, with an LOD of 0.40 microg/mL (1.31 x 10(-6) M) and an LOQ of 1.21 microg/mL. The suggested method was successfully applied for the analysis of risedronate in raw material and a tablet formulation, with average recoveries of 99.91 +/- 1.30 and 101.52 +/- 0.30%, respectively. The stability-indicating capability of the proposed method was proved using forced degradation. By changing the pH of the mobile phase to 4.0, the oxidative degradation product could be separated from risedronate.     

Spectrophotometric, spectrofluorometric and HPLC determination of desloratadine in dosage forms and human plasma

Four sensitive, simple and specific methods were developed for the determination of desloratadine (DSL), a new antihistaminic drug in pharmaceutical preparations and biological fluids. Methods I and II are based on coupling DSL with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.6 where a yellow colored reaction product was obtained and measured spectrophotometrically at 485 nm (Method I). The same product could be measured spectrofluorometrically at 538 nm after excitation at 480 nm (Method II). Methods III and IV, on the other hand, involved derivatization of DSL with 2,4-dinitrofluorobenzene (DNFB) in borate buffer of pH 9.0 producing a yellow colored product that absorbs maximally at 375 nm (Method III). The same derivative was determined after separation adopting HPLC (Method IV). The separation was performed on a column packed with cyanopropyl bonded stationary phase equilibrated with a mobile phase composed of acetonitrile-water (60 : 40, v/v) at a flow rate of 1.0 ml min(-1) with UV detection at 375 nm. The calibration curves were linear over the concentration ranges of 0.5-6, 0.02-0.4, 1-10 and 1-30 microg ml(-1) for Methods I, II, III and IV, respectively. The lower detection limits (LOD) were 0.112, 0.004, 0.172 and 0.290 microg ml(-1), respectively, for the four methods. The limits of quantification (LOQ) were 0.340, 0.012, 0.522 and 0.890 microg ml(-1) for Methods I, II, III and IV, respectively. The proposed methods were applied to the determination of desloratadine in its tablets and the results were in agreement with those obtained using a reference method. Furthermore, the spectrofluorometric method (Method II) was extended to the in-vitro determination of the drug in spiked human plasma, with a mean percentage recovery (n=4) of 99.7+/-3.54. Interference arising from endogenous amino acids has been overcome using solid phase extraction. The proposed methods are highly specific for determination of DSL in the presence of the parent drug loratadine. A proposal for the reaction pathways is postulated.     

A stability indicating assay method for cefuroxime axetil and its application to analysis of tablets exposed to accelerated stability test conditions

Cefuroxime axetil is the esterified form of cefuroxime, injectable second generation cephalosporine antibiotic that can be given orally. Stereo and structural isomers of cefuroxime axetil (CA), anti-cefuroxime axetil (ACA) and Delta(3)-cefuroxime axetil (DCA), can be present in cefuroxime dosage forms as the process related impurities as well as possible degradation product. Sensitive and precise reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the determination of cefuroxime axetil in the presence of its degradation products in solid dosage forms. The RSD values for cefuroxime axetil, anti-cefuroxime axetil and Delta(3)-cefuroxime axetil of 1.80, 1.99 and 2.48%, respectively, indicated a good precision of the RP-HPLC method. Developed RP-HPLC method was sensitive with LOD = 0.08 microg mL(-1) and LOQ = 0.60 microg mL(-1) for anti-cefuroxime axetil and LOD = 0.06 microg mL(-1) and LOQ = 0.45 microg mL(-1) for Delta(3)-cefuroxime axetil. Holding studies were carried out on Ceroxim tablets, according to ICH regulation at 30 degrees C/60% relative humidity (RH) and 40 degrees C/75% RH for 1, 2, 3 and 6 months. The review data from the stability studies conducted, show the significant content change of Delta(3)-cefuroxime axetil.     

Forced Degradation Study on Gliclazide and Application of Validated Stability-Indicating HPLC-UV Method in Stability Testing of Gliclazide Tablets

Forced degradation study on gliclazide was conducted under the conditions of hydrolysis, oxidation, dry heat and photolysis and an isocratic stability-indicating HPLC-UV method was developed and validated. All the seven degradation products (I–VII) formed under different conditions were optimally resolved on a C₁₈ column with mobile phase composed of 40% acetonitrile and 60% ammonium acetate solution (0.025 M, pH 3.5) at a flow rate of 0.25 mL min^?1 using 235 nm as detection wavelength. The method was linear between 5–500 μg mL^?1 drug concentrations. The %RSD of intra- and inter-day precision studies was <1 and <2% respectively. Excellent recoveries (99.81–100.97%) proved the method sufficiently accurate. Each peak resolved always with a resolution of >1.90 indicating the method to be rugged enough. The method was used to study the drug degradation behaviour under the forced conditions. Four degradation products (I–IV) were formed in 0.1 N HCl and water whereas only I and III were formed in 3% H₂O₂. Two new products V and VI in addition to I, III and IV were formed in 0.1 N NaOH. The drug was stable to thermal and photolytic decomposition. The degradation behaviour in water and 0.1 N NaOH was similar under dark and light conditions but a new product VII was formed in 0.01 N HCl in light. In general, the rate of degradation was accelerated by the light. The method was applied successfully in stability testing of gliclazide tablets.     

Development and validation of a stability-indicating RP-HPLC method for determination of atomoxetine hydrochloride in tablets

This paper describes the development of a stability-indicating RP-HPLC method for the determination of atomoxetine hydrochloride (ATX) in the presence of its degradation products generated from forced decomposition studies. The drug substance was subjected to stress conditions of acid, base, oxidation, wet heat, dry heat, and photodegradation. In stability tests, the drug was susceptible to acid, base, oxidation, and dry and wet heat degradation. It was found to be stable under the photolytic conditions tested. The drug was successfully separated from the degradation products formed under stress conditions on a Phenomenex C18 column (250 x 4.6 mm id, 5 microm particle size) by using acetonitrile-methanol-0.032 M ammonium acetate (55 + 05 + 40, v/v/v) as the mobile phase at 1.0 mL/min and 40 degrees C. Photodiode array detection at 275 nm was used for quantitation after RP-HPLC over the concentration range of 0.5-5 microg/mL with a mean recovery of 100.8 +/- 0.4% for ATX. Statistical analysis demonstrated that the method is repeatable, specific, and accurate for the estimation of ATX. Because the method effectively separates the drug from its degradation products, it can be used as a stability-indicating method.     

A simple and sensitive stability-indicating RP-HPLC assay method for the determination of aceclofenac

The aim of the present study is to develop a stability-indicating assay method for the determination of aceclofenac after being subjected to different International Conference on Harmonization prescribed stress conditions, such as hydrolysis, oxidation, heat, and photolysis. Aceclofenac (2-[2-[2-(2,6-dichlorophenyl)aminophenyl]acetyl]oxyacetic acid) is decomposed under hydrolytic stress (neutral, acidic, and alkaline) and also on exposure to light (in solution form). The compound is stable to oxidative stress, heat, and photolytic stress (in solid form). The major degradation product is diclofenac, which is confirmed through comparison with the standard. Separation of the drug from major and minor degradation products is achieved on a C-18 column using methanol-0.02% of ortho phosphoric acid in a ratio of 70:30. The method is linear over the concentration range of 17-100 microg/mL (r(2) = 0.9988). The detection wavelength is 275 nm. The method is validated for linearity, range, precision, accuracy, specificity, and selectivity.     

LC and LC-MS study on establishment of degradation pathway of glipizide under forced decomposition conditions

Forced degradation studies on glipizide are conducted under the conditions of hydrolysis, oxidation, photolysis, and dry heat. The solutions are subjected to liquid chromatographic (LC) investigations to establish the number of products formed in each condition. The degradation products are characterized through isolation and subsequent NMR, IR, and MS spectral analyses, or through LC-mass spectrometry (MS) fragmentation pattern study. The drug is shown to degrade in 0.1M HCl at 85 degrees C to two products: 5-methyl-N-[2-(4-sulphamoylphenyl)ethyl]pyrazine-2-carboxamide (II) and methyl N-[4-[2-{(5-methyl-2-pyrazinoyl)amino}ethyl] phenyl]sulfonyl carbamate (III). The latter, a methyl ester, is formed only in the presence of methanol (used as a solubilizer), and does not appear on use of acetonitrile. III is shown to convert to II on continued heating in acid. The drug degrades slowly in water at the same temperature, and both II and III could be seen in the chromatograms until the end of the study. The heating of the drug in alkali (0.1M NaOH) at 85 degrees C yields 5-methyl-2-pyrazinecarboxylic acid (IV), along with a small quantity of 4-(2-aminoethyl) benzenesulfonamide (I). On extended heating in the same condition, a new product, 4-(2-aminoethyl)-N,N-bis[(cyclohexylamino)carbonyl] benzenesulfonamide (VI) is formed in small quantities. At the lower temperature of 40 degrees C, the drug converts under each hydrolytic condition and in both the absence and presence of light to products II, III, or IV, along with a new product, 1-cyclohexyl-3-[[4-(2aminoethyl)phenyl] sulfonyl]urea (V). The light catalyzes formation of V, and it is formed until one or two weeks, after which its level decreases. The drug remains stable in 30% H2O2, except that products II and III appear as small peaks due to acidic character of the peroxide solution. Also, the drug remains unaffected in solid state under thermal and photolytic stress conditions. Based on the results, a more complete picture on degradation pathway of the drug is obtained, highlighting a clear advantage of the approach suggested by International Conference on Harmonization.     

MS2/TOF and LC-MS/TOF studies on toremifene to characterize its forced degradation products

The present study was designed to characterize the possible degradation products of toremifene under varied conditions as prescribed by ICH guidelines Q1A(R2). The forced degradation studies were conducted on toremifene citrate under the conditions of hydrolysis (acidic, basic and neutral), photolysis, oxidation and dry heat. The drug was found unstable to photolysis and hydrolysis in water and acidic media but stable to alkaline hydrolysis, peroxide oxidation and thermal degradation. In total fifteen degradation products (I-XV) were formed, which were resolved from each other and the drug on a C-18 column employing an isocratic elution method. A complete mass fragmentation pattern of the drug was established with the help of LC/ESI-MS/TOF to assist characterization of the degradation products. Of the fifteen products, six products III, IV, VII, VIII, XIV and XV were detected in LC-MS. The molecular masses of III, IV, VII and VIII were found to be the same i.e., 387, while those of XIV and XV were 389 and 403, respectively. Structures of these products were elucidated through comparison of their mass fragmentation patterns with the drug, which were proposed on the basis of accurate masses of the parent and fragment ions. These were characterized as (Z)-2-(2-(dimethylamino)ethyl)-4-(4-hydroxy-1,2-diphenylbut-1-enyl)phenol (III), (E)-2-(2-(dimethylamino)ethyl)-4-(4-hydroxy-1,2-diphenylbut-1-enyl)phenol (IV), (E)-4-(4-(2-(dimethylamino)ethoxy)phenyl)-3,4-diphenylbut-3-en-1-ol (VII), (Z)-4-(4-(2-(dimethylamino)ethoxy)phenyl)-3,4-diphenylbut-3-en-1-ol (VIII), 2-(4-(10-(2-chloroethyl)phenanthren-9-yl)phenoxy)-N-methylethanamine (XIV), and 2-(4-(10-(2-chloroethyl)phenanthren-9-yl)phenoxy)-N,N-dimethylethanamine (XV). Finally, a most plausible mechanistic explanation for degradation of the drug in different chemical environments is also proposed. The results of the study disclose six new degradation related impurities of the drug.     

Validated stability indicating LC method for carprofen: characterization of degradation products by MS

A simple, sensitive, and selective stability indicating high performance liquid chromatographic method has been developed and validated for quantitative analysis of carprofen (CPF) in presence of its degradation products. All degradation products in acid hydrolysis and photolysis were separated, identified by mass spectroscopic method and probable structures were elucidated. The forced degradation studies were performed on a bulk sample of CPF by using various methods like 0.1 M hydrochloric acid, 0.1 M sodium hydroxide, 0.33% hydrogen peroxide (H(2)O), heating at 60°C and exposure to UV light at 254 nm. A 5 μm particle octa desyl silane (ODS) column (150 mm × 4.6 mm) was used with acetonitrile-ammonium acetate (100 mM, pH-6.7) 40:60 (v/v) as a mobile phase at flow rate of 1.2 mL/min. Column oven temperature was maintained at 30°C and quantitation was achieved at 239 nm on the basis of peak area. The linear range and correlation coefficient (r(2)) was found 0.5-60 μg/mL and 0.9999 respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were obtained 0.066 μg/mL and 0.20 μg/mL respectively . The proposed method was found to be suitable and accurate for quantitative analysis, stability study and characterisation of degradation product of CPF.     

Smart stability-indicating spectrophotometric methods for determination of binary mixtures without prior separation

Ratio subtraction and isosbestic point methods are 2 innovating spectrophotometric methods used to determine vincamine in the presence of its acid degradation product and a mixture of cinnarizine (CN) and nicergoline (NIC). Linear correlations were obtained in the concentration range from 8-40 microg/mL for vincamine (I), 6-22 microg/mL for CN (II), and 6-36 microg/mL for NIC (III), with mean accuracies 99.72 +/- 0.917% for I, 99.91 +/- 0.703% for II, and 99.58 +/- 0.847 and 99.83 +/- 1.039% for III. The ratio subtraction method was utilized for the analysis of laboratory-prepared mixtures containing different ratios of vincamine and its degradation product, and it was valid in the presence of up to 80% degradation product. CN and NIC in synthetic mixtures were analyzed by the 2 proposed methods with the total content of the mixture determined at their respective isosbestic points of 270.2 and 235.8 nm, and the content of CN was determined by the ratio subtraction method. The proposed method was validated and found to be suitable as a stability-indicating assay method for vincamine in pharmaceutical formulations. The standard addition technique was applied to validate the results and to ensure the specificity of the proposed methods.     

HPLC, TLC, and first-derivative spectrophotometry stability-indicating methods for the determination of tropisetron in the presence of its acid degradates

Three stability-indicating assay methods were developed for the determination of tropisetron in a pharmaceutical dosage form in the presence of its degradation products. The proposed techniques are HPLC, TLC, and first-derivative spectrophotometry (1D). Acid degradation was carried out, and the degradation products were separated by TLC and identified by IR, NMR, and MS techniques. The HPLC method was based on determination of tropisetron in the presence of its acid-induced degradation product on an RP Nucleosil C18 column using methanol-water-acetonitrile-trimethylamine (65 + 20 + 15 + 0.2, v/v/v/v) mobile phase and UV detection at 285 nm. The TLC method was based on the separation of tropisetron and its acid-induced degradation products, followed by densitometric measurement of the intact spot at 285 nm. The separation was carried out on silica gel 60 F254 aluminum sheets using methanol-glacial acetic acid (22 + 3, v/v) mobile phase. The 1D method was based on the measurement of first-derivative amplitudes of tropisetron in H2O at the zero-crossing point of its acid-induced degradation product at 271.9 nm. Linearity, accuracy, and precision were found to be acceptable over concentration ranges of 40-240 microg/mL, 1-10 microg/spot, and 6-36 micro/mL for the HPLC, TLC, and 1D methods, respectively. The suggested methods were successfully applied for the determination of the drug in bulk powder, laboratory-prepared mixtures, and a commercial sample.     

Enantioselective HPLC-UV method for determination of eslicarbazepine acetate (BIA 2-093) and its metabolites in human plasma

Eslicarbazepine acetate (BIA 2-093) is a novel central nervous system drug undergoing clinical phase III trials for epilepsy and phase II trials for bipolar disorder. A simple and reliable chiral reversed-phase HPLC-UV method was developed and validated for the simultaneous determination of eslicarbazepine acetate, oxcarbazepine, S-licarbazepine and R-licarbazepine in human plasma. The analytes and internal standard were extracted from plasma by a solid-phase extraction using Waters Oasis HLB cartridges. Chromatographic separation was achieved by isocratic elution with water-methanol (88:12, v/v), at a flow rate of 0.7 mL/min, on a LichroCART 250-4 ChiraDex (beta-cyclodextrin, 5 microm) column at 30 degrees C. All compounds were detected at 225 nm. Calibration curves were linear over the range 0.4-8 microg/mL for eslicarbazepine acetate and oxcarbazepine, and 0.4-80 microg/mL for each licarbazepine enantiomer. The overall intra- and interday precision and accuracy did not exceed 15%. Mean relative recoveries varied from 94.00 to 102.23% and the limit of quantification of the assay was 0.4 microg/mL for all compounds. This method seems to be a useful tool for clinical research and therapeutic drug monitoring of eslicarbazepine acetate and its metabolites S-licarbazepine, R-licarbazepine and oxcarbazepine.     

Determination of carbamazepine and its impurities iminostilbene and iminodibenzyl in solid dosage form by column high-performance liquid chromatography

An accurate and precise RP-HPLC method was developed and validated for the determination of carbamazepine and its impurities iminostilbene and iminodibenzyl in a tablet formulation with fluphenazine as an internal standard. Buffer-methanol (50 + 50, v/v) was used as the mobile phase. During validation, specificity, linearity, precision, accuracy, LOD, LOQ, and robustness of the method were tested. The method was proven to be specific against placebo interference. Linearity was evaluated over the concentration range of 100-500, 0.05-0.25, and 0.1-0.5 microg/mL, and the r values were 0.9994, 0.9997, and 0.9979 for carbamazepine, iminostilbene, and iminodibenzyl, respectively. Intraday precision of the method was good, and RSD was below 2% for all analytes. The accuracy of the method ranged from 100.69 to 102.10, 99.76 to 102.66, and 99.26 to 100.08% for carbamazepine, iminostilbene, and iminodibenzyl, respectively. LOD was 0.0125, 0.025, and 0.05 microg/mL and LOQ was 0.05, 0.05, and 0.1 microg/mL for carbamazepine, iminostilbene, and iminodibenzyl, respectiviely. Robustness of the method was proven by using a chemometric approach. The method was successfully applied to the analysis of commercially available carbamazepine tablets and showed good repeatability, with RSD below 2%.     

Fractional wavelet analysis for the simultaneous quantitative analysis of lacidipine and its photodegradation product by continuous wavelet transform and multilinear regression calibration

Fractional wavelet transform (FWT) was applied to the original absorption spectra of lacidipine (LAC) and its photodegradation product (LACD), and the resulting FWT spectra were processed by continuous wavelet transform (CWT) and multilinear regression calibration (MLRC) for the simultaneous quantitative analysis of both products in their binary mixtures. These methods do not require any chemical separation step and chemical complex reaction to obtain a detectable signal for the degradation product. By using the Mexican hat function, 2 calibration functions for LAC and LACD were obtained by measuring the CWT transformed signals at 416.1 nm for LAC and 414.6 nm for LACD, after FWT processing of the original absorption spectra. The calibration graphs were linear in the concentration range of 5.08-40.64 microg/mL for LAC and 0.51-8.16 microg/mL for LACD. The limit of detection and the limit of quantitation were found to be 0.289 and 0.956 microg/mL for LAC and 0.036 and 0.118 microg/mL for LACD, respectively. For comparison, the MLRC algorithm was applied to the linear regression functions for the individual drug and its photoproduct. In this approach, a set of linear regression functions was obtained from the relationship between concentrations and FWT signals in the wavelength range 411.0-412.4 nm. Both methods were applied to the quantitative evaluation of LAC and LACD in laboratory and pharmaceutical samples, and produced very satisfactory results.     

Quantitative impurity analysis of monoclonal antibody size heterogeneity by CE-LIF: example of development and validation through a quality-by-design framework

This paper describes the framework of quality by design applied to the development, optimization and validation of a sensitive capillary electrophoresis-sodium dodecyl sulfate (CE-SDS) assay for monitoring impurities that potentially impact drug efficacy or patient safety produced in the manufacture of therapeutic MAb products. Drug substance or drug product samples are derivatized with fluorogenic 3-(2-furoyl)quinoline-2-carboxaldehyde and nucleophilic cyanide before separation by CE-SDS coupled to LIF detection. Three design-of-experiments enabled critical labeling parameters to meet method requirements for detecting minor impurities while building precision and robustness into the assay during development. The screening design predicted optimal conditions to control labeling artifacts while two full factorial designs demonstrated method robustness through control of temperature and cyanide parameters within the normal operating range. Subsequent validation according to the guidelines of the International Committee of Harmonization showed the CE-SDS/LIF assay was specific, accurate, and precise (RSD ≤ 0.8%) for relative peak distribution and linear (R > 0.997) between the range of 0.5-1.5 mg/mL with LOD and LOQ of 10 ng/mL and 35 ng/mL, respectively. Validation confirmed the system suitability criteria used as a level of control to ensure reliable method performance.     

Stress Degradation Studies of Anagliptin,Development of Validated Stability Indicating Method,Degradation Kinetics Study,Identification and Isolation of Degradation Products

A gradient-specific stability indicating HPLC method was developed and validated for the determination of the antidiabetic agent anagliptin in laboratory mixtures. Reversed-phase chromatography was performed using a Shimadzu LC-20 AD pump (binary), Shimadzu PDA M-20A diode array detector, and Waters Symmetry C-18 column (150?×?4.6 mm, 3.5 µm) maintained at a column oven temperature of 40 °C with UV detection at 247 nm. A gradient program was run at flow rate of 1 mL min^?1. Mobile phase A consisted of a mixture of acetate buffer(10 mm) pH 5/methanol/acetonitrile in the ratio of 90:5:5. Mobile phase B consisted of a mixture of acetate buffer (10 mm) pH 5/methanol/acetonitrile in the ratio of 50:25:25. The method was validated according International Conference of Harmonization (ICH) guidelines. Linearity was observed in the concentration range of 10–120 µg/mL with regression coefficient r²(0.999). The LOD was found to be 7.8 µg/mL and LOQ was found to be 22.68 µg/mL. Anagliptin was subjected to stresses such as acidic, alkali, oxidation, photolysis, and thermal conditions. The proposed method was validated as per ICH guidelines and was found to be accurate, precise, and specific. The drug showed significant degradation in alkaline and oxidative conditions. Alkaline and oxidative degradation followed first-order kinetics. Degradation rate constant and half-lives were determined. Degradation products in alkaline and oxidative conditions were identified by LC–MS. One major degradation product was isolated from each condition by preparative HPLC. These degradation products were characterized by ¹H NMR, ¹³C NMR, DEPT, D₂O exchange, MS/MS, HRMS, and IR techniques. From the spectral data the alkaline degradation product was characterized as 1-{2-[1-(2-methylpyrazolo[1,5-a]pyrimidine-6-carboxamido)-methyl-propan-2-yl-amino]acetyl}pyrrolidine-2-carboxamide. The oxidative degradation product was characterized as N-[2-({2-[(2S)-2-cyanopyrrolidin-1-yl]-2-oxoethyl}amino)-2-methylpropyl]-2-methylpyrazolo-[1,5-a]pyrimidine-N-oxido-6-carboxamide.     

Development and validation of a column high-performance liquid chromatography method for quantification of ganaphaliin A and B in inflorescences of Gnaphalium liebmannii Sch. Bp ex Klatt

An HPLC method was developed for the simultaneous determination of gnaphaliin A and B, active compounds of Gnaphalium liebmannii Sch. Bp ex Klatt. The HPLC separation was performed on an Inertsil ODS-3 (150 x 4.6 mm id, 5 microm) RP C18 column operated at 40 degrees C; the isocratic mobile phase was 0.02% aqueous orthophosphoric acid-methanol-acetonitrile (50 + 30 + 20, v/v/v), with a run time of 20 min and flow rate of 1.5 mL/min. Detection with a photodiode array detector (PDAD) was at 270 nm. The method was validated for linearity, repeatability, LOD, and LOQ. The LOD and LOQ for gnaphaliin A and B were found to be in the range of 0.4-0.5 and 1.0-1.4 microg/mL, respectively. This is the first report of an analytical method developed for the quantitative analysis of flavones from Gnaphalium species by HPLC-PDAD with applications for raw material and commercial products.     

Development and validation of a reversed-phase ultra-performance liquid chromatographic method for assay of lacidipine and related substances

A simple isocratic, RP-ultra-performance LC method was developed and validated for the determination of lacidipine, three process impurities formed during synthesis, and three degradation products present in drug substance and the drug product. An efficient chromatographic separation was achieved on an Acquity BEH C18 column using pH 4.5 ammonium acetate-acetic acid buffer-methanol (70 + 30, v/v) mobile phase. The monitoring wavelength was 240 nm, and the flow rate 0.25 mL/min. Forced degradation studies using acid, alkali, peroxide, water, heat, and light were conducted, and all impurities were separated. The method was validated successfully for specificity, precision, linearity, accuracy, LOD, LOQ, and robustness, according to International Conference on Harmonization guidelines. The linearity of the calibration curve for lacidipine and each impurity was found to be very good (r2 > 0.999). This method is shown to be suitable for analysis of lacidipine to evaluate the quality of drug substance and a drug product.     

Characterization of fluvalinate residues in honey by gas chromatography–atomic emission detection and gas chromatography–mass spectrometry

Two hyphenated techniques, gas chromatography–mass spectrometry and gas chromatography–atomic emission detection, have been used to identify the degradation products of the acaricide fluvalinate in a methanol solution of the commercially available formulation Mavrick, as well as in honey from beehives treated with this product. The major degradation products were 2-chloro-4-trifluoromethylaniline (I), methyl 2-[2-chloro-4-trifluoromethylaniline]-3-methylbutanoate (II), N-(2-chloro-4-trifluoromethyl-phenyl)valine (III), and 3-phenoxybenzaldehyde (IV). Fluvalinate in honey is gradually degraded, 3-phenoxybenzaldehyde being the most abundant residue.     

Determination of uranium, iron, copper, and nickel from ore samples by MEKC using N,N'-ethylene bis(salicylaldimine) as complexing reagent

An analytical procedure has been developed for the separation of dioxouranium(VI), iron(III), copper(II), nickel(II), cobalt(II), cobalt(III), palladium(II), and thorium(IV) by MEKC using N,N'-ethylene bis(salicylaldimine) (H(2)SA(2)en) as a complexing reagent with total runtime <4.5 min. SDS was used as micellar medium at pH 8 with sodium tetraborate buffer (0.1 M). An uncoated fused-silica capillary with an effective length of 50 cm x 75 microm id was used with an applied voltage of 30 kV with photodiode array detection at 231 nm. Linear calibrations were obtained within 0.111-1000 microg/mL of each element with LODs within 37-325 ng/mL. The developed method was tested for analysis of uranium ore samples indicating its presence within 103-1789 microg/g with RSD within 0.79-1.87%. Likewise copper, nickel, and iron in their combined matrix were also simultaneously determined with RSD 0.4-1.6% (n = 6).