Determination of some antiemetic drugs through its native fluorescence or fluorescence quenching of cerrous ammonium sulphate.

The manuscript describes two fluorimetric methods for the determination of some antiemetic drugs namely granisetron HCl, ondansetron HCl and tropisetron HCl, used in the management of nausea and vomiting induced by cytotoxic chemotherapy and radiotherapy. Granisetron HCl solution exhibits a native fluorescence, which can be applied for its determination at 365 nm upon excitation at 305 nm. The method was applied for the determination of granisetron HCl in drug substance, drug product as well as in presence of its acid induced degradation products. The quantum yield was calculated. The second proposed method is based on measuring the quenching effect induced by ondansetron HCl or tropisetron HCl on the fluorescence intensity of cerrous ammonium sulphate at λem 348 nm upon excitation at 250 nm in acidic medium. The analysis of quenching data showed that quenching of cerrous ammonium sulphate induced by ondansetron HCl or tropisetron HCl is mainly through dynamic quenching. Various variables affecting fluorescence response were studied and optimized. The obtained results were found to be statistically agreed with those obtained from the official or reported ones. Moreover, the validity of the methods was assessed according to ICH guidelines.

Novel spectrophotometric methods for the determination of Leflunomide and Diacerein in binary mixtures.

Two novel spectrophotometric methods were presented in this work using ethanol as a solvent. The first method was the ratio difference spectrophotometric method [RDSM], in which the amplitude difference between two selected wavelengths on the ratio spectra were recorded and used for estimation of each of Leflunomide LEF in mixture with its alkaline induced degradate DEG and also for Diacerein DIA determination in mixture with Aceclofenac ACEC without interference from the other component in the mixture. The second method is the ratio subtraction coupled with constant multiplication [RS-CM], where LEF was determined in its mixture with its alkaline degradate DEG at 261 nm which is considered as a stability indicating assay. In addition to simultaneous determination of Diacerein DIA and Aceclofenac ACEC in their mixtures at 257 and 277 nm, respectively, by the second method without previous separation. Linearity was shown over the concentration range of [1.5-15 µg/ml] for LEF, [1-11 µg/ml] for DIA and [2.5-25 µg/ml] for ACEC, by both proposed methods. Leflunomide was found to be completely degraded when subjected to alkaline degradation producing one alkaline product. Validation of the suggested methods was conducted according to ICH guidelines, concerning precision, accuracy, repeatability. The suggested spectrophotometric methods were statistically compared to reference methods showing no significant difference. The suggested spectrophotometric methods are considered to be simple, sensitive and could be easily applied in quality control laboratories instead of LC methods.

A Validated HPLC Method for Simultaneous Determination of Perindopril Arginine, Amlodipine, and Indapamide: Application in Bulk and in Different Pharmaceutical Dosage Forms.

A simple, accurate, and precise LC method with a reversed stationary phase was developed and validated for the determination of perindopril (PER) arginine, amlodipine (AML), and indapamide (IND) alone and in binary mixtures (PER arginine is found in two dosage forms, i.e., with either AML or IND). Chromatographic separation was carried out on a BDS Hypersil® C18 column (100 × 3 mm, 5 µm). The mobile phase, consisting of 0.05 M potassium dihydrogen phosphate buffer (pH 2.6)-methanol (50 + 50, v/v), was pumped through the column whose temperature was maintained at 50°C at a flow rate of 0.6 mL/min using isocratic elution, and UV detection at 215 nm was performed. Acceptable values of linearity, accuracy, and precision of the method were found over the concentration ranges of 5-80 µg/mL PER, 2.5-80 µg/mL AML, and 0.5-20 µg/mL IND. The proposed chromatographic method was statistically compared to that of reference methods using one-way analysis of variance. The results showed that there was no significant difference between the methods. The developed method proved reliable for use in accurate QC of the drugs in their pharmaceutical preparations.

Validated spectrofluorimetric methods for the determination of apixaban and tirofiban hydrochloride in pharmaceutical formulations.

Apixaban and Tirofiban Hydrochloride are low molecular weight anticoagulants. The two drugs exhibit native fluorescence that allow the development of simple and valid spectrofluorimetric methods for the determination of Apixaban at λ ex/λ em=284/450nm and tirofiban HCl at λ ex/λ em=227/300nm in aqueous media. Different experimental parameters affecting fluorescence intensities were carefully studied and optimized. The fluorescence intensity-concentration plots were linear over the ranges of 0.2-6µgml-1 for apixaban and 0.2-5µgml-1 for tirofiban HCl. The limits of detection were 0.017 and 0.019µgml-1 and quantification limits were 0.057 and 0.066µgml-1 for apixaban and tirofiban HCl, respectively. The fluorescence quantum yield of apixaban and tirofiban were calculated with values of 0.43 and 0.49. Method validation was evaluated for linearity, specificity, accuracy, precision and robustness as per ICH guidelines. The proposed spectrofluorimetric methods were successfully applied for the determination of apixaban in Eliquis tablets and tirofiban HCl in Aggrastat intravenous infusion. Tolerance ratio was tested to study the effect of foreign interferences from dosage forms excipients. Using Student's t and F tests, revealed no statistically difference between the developed spectrofluorimetric methods and the comparison methods regarding the accuracy and precision, so can be contributed to the analysis of apixaban and tirofiban HCl in QC laboratories as an alternative method.

Stability-Indicating RP-HPLC Methods for the Determination of Fluorometholone in Its Mixtures with Sodium Cromoglycate and Tetrahydrozoline Hydrochloride.

Two stability-indicating reversed-phase liquid chromatographic methods were developed and validated for the determination of fluorometholone (FLU) in its mixtures with sodium cromoglycate (SCG) and tetrahydrozoline hydrochloride (THZ). The first HPLC method (Method 1) was based on isocratic elution of FLU and SCG along with their alkaline degradation products on a reversed phase C18 column (250 × 4.6 mm id)-ACE Generix 5, using a mobile phase consisting of methanol-water (70 : 30, v/v), pH adjusted to 2.5 using orthophosphoric acid at a flow rate of 1.2 mL min(-1) Quantitation was achieved with UV detection at 240 nm. The second HPLC method (Method 2) was based on isocratic elution of FLU, its alkaline degradation product and THZ on a reversed phase C8 column (250 × 4.6 mm)-ACE Generix 5, using a mobile phase consisting of acetonitrile-50 mM potassium dihydrogen orthophosphate (40 : 60, v/v) at a flow rate of 2 mL min(-1) Quantitation was achieved by applying dual-wavelength detection, where FLU and its alkaline degradation product were detected at 240 nm and THZ was detected at 215 nm at ambient temperatures. Linearity, accuracy and precision were found to be acceptable over the concentration range of 5-50 and 10-500 µg mL(-1) for FLU and SCG (Method 1) and over the concentration range of 5-80 and 5-60 µg mL(-1) for FLU and THZ (Method 2), respectively. Besides, the FLU alkaline degradation product was verified using IR, NMR and LC-MS spectroscopy. The two proposed methods could be successfully applied for the routine analysis of the studied drugs either in their pure bulk powders or in their pharmaceutical preparations without any preliminary separation step.

Novel liquid chromatographic methods for the determination of varenicline tartrate.

Two simple, sensitive, rapid, and stability-indicating liquid chromatographic (LC) methods have been developed for the determination of varenicline tartrate. They comprised the determination of varenicline (VRC) in the presence of its oxidative degradates and related impurity (N-formyl varenicline) (NFV). The first method was a LC with diode array detection (DAD) at 235 nm using Ristek-Ultra® C18 column (100 mm × 2.1 mm, 5 µm). Isocratic elution of VRC was employed using a mobile phase consisting of buffer mixture (1.2% potassium dihydrogen phosphate and 0.08% octane sulphonic acid): acetonitrile (86:14, v/v), pH (5.0). In the second method; a fluorimetric detection technique was developed, based on precolumn derivatization of VRC using 7-chloro-4-nitrobenzo-2-oxa-1, 3-diazole (NBD-Cl). The fluorescence detector (FLD) was operated at 474 nm for excitation and 539 nm for emission. Isocratic elution was applied with a mobile phase consisting of methanol-distilled water (70:30, v/v). Separation was achieved using Symmetry® Waters C18 column (150 mm × 4.6 mm, 5 µm). Linearity, accuracy and precision were found to be acceptable over the concentration ranges of 0.5-20.0 µg mL(-1) and 0.2-20.0 µg mL(-1) with the first and the second method, respectively. The optimized methods were validated and proved to be specific, simple, and accurate for the quality control of the drug in its pharmaceutical preparation.

Validated HPLC and Ultra-HPLC Methods for Determination of Dronedarone and Amiodarone Application for Counterfeit Drug Analysis.

Two simple, accurate, and precise chromatographic methods have been developed and validated for the determination of dronedarone (DRO) HCl and amiodarone (AMI) HCl either alone or in binary mixtures due to the possibility of using AMI as a counterfeit of DRO because of its lower price. First, an RP-HPLC method is described for the simultaneous determination of DRO and AMI. Chromatographic separation was achieved on a BDS Hypersil C18 column (150×4.6 mm, 5 µm). Isocratic elution based on potassium dihydrogen phosphate buffer with 0.1% triethylamine pH 6-methanol (10+90, v/v) at a flow rate of 2 mL/min with UV detection at 254 nm was performed. The second method is RP ultra-HPLC in which the chromatographic separation was achieved on an AcclaimTM RSLC 120 C18 column (100×2.1 mm, 2.2 µm) using isocratic elution with potassium dihydrogen phosphate buffer with 0.1% triethylamine pH 6-methanol (5+95, v/v) at a flow rate of 1 mL/min with UV detection at 254 nm. Linearity, accuracy, and precision of the two methods were found to be acceptable over the concentration ranges of 5-80 µg/mL for both DRO and AMI. The results were statistically compared using one-way analysis of variance. The optimized methods were validated and proved to be specific, robust, precise, and accurate for the QC of the drugs in their pharmaceutical preparations.

Simultaneous Determination of Aliskiren Hemifumarate, Amlodipine Besylate and Hydrochlorothiazide in Spiked Human Plasma Using UPLC-MS/MS.

A sensitive UPLC-MS/MS method was developed and validated for simultaneous estimation of aliskiren hemifumarate (ALS), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) in spiked human plasma using valsartan as an internal standard (IS). Liquid-liquid extraction was used for purification and pre-concentration of analytes. The mobile phase consisted of 0.1% formic acid in ammonium acetate buffer (0.02 M, pH 3.5) and methanol (25:75, v/v), flowing through XBridge BEH (50 × 2.1 mm ID, 5 µm) C18 column, at a flow rate of 0.6 mL min(-1). Multiple reaction monitoring (MRM) transitions were measured using an electrospray source in the positive ion mode for ALS and AML, whereas HCZ and IS were measured in negative ion mode. Validation of the method was performed as per US-FDA guidelines with linearity in the range of 2.0-400.0, 0.3-25.0 and 5.0-400.0 ng mL(-1) for ALS, AML and HCZ, respectively. In human plasma, ALS, AML and HCZ were stable for at least 1 month at -70 ± 5°C and for at least 6 h at ambient temperature. After extraction from plasma, the reconstituted samples of ALS, AML and HCZ were stable in the autosampler at ambient temperature for 6 h. The LC-MS/MS method is suitable for bioequivalence and pharmacokinetic studies of this combination.

Stability-indicating RP-LC method for determination of azilsartan medoxomil and chlorthalidone in pharmaceutical dosage forms: application to degradation kinetics.

A RP-LC method was developed and validated for simultaneous determination of the active components, azilsartan medoxomil (AZL) and chlorthalidone (CLT), in their novel antihypertensive combined recipe. The chromatographic separation was achieved on an Eclipse XDB-C18 (4.6 × 150 mm, 5 µm) column using a mobile phase consisting of methanol/potassium hydrogen phosphate buffer (pH 8, 0.05 M) (40:60, v/v) in isocratic mode. The flow rate was maintained at 0.8 mL min(-1) at ambient temperature. Detection was carried out at 210 nm. The method was validated according to the ICH guidelines. Linearity, accuracy, and precision were satisfactory over the concentration range of 5.0-50.0 and 2.5-25.0 µg mL(-1) for AZL and CLT, respectively (r (2) = 0.9999). LODs for AZL and CLT were 0.90 and 0.32 µg mL(-1), whereas LOQs were 2.72 and 0.98 µg mL(-1), respectively. Both drugs were subjected to forced degradation studies under hydrolysis (neutral, acidic, and alkaline), oxidative, and photolytic extensive stress conditions. The proposed method is stability indicating by the resolution of the investigated drugs from their degradation products. Moreover, the kinetics of the acidic degradation of AZL as well as the kinetics of the alkaline degradation of CLT were investigated. Arrhenius plots were constructed and the apparent first-order rate constants, half-life times, shelf-life times, and the activation energies of the degradation processes were calculated. The method was successfully applied for the determination of the studied drugs simultaneously in their coformulated tablet. The developed method is specific and stability indicating for the quality control and routine analysis of the cited medications in their pharmaceutical preparations.

Spectrophotometric and spectrofluorimetric studies on azilsartan medoxomil and chlorthalidone to be utilized in their determination in pharmaceuticals.

The recently approved angiotensin II receptor blocker, azilsartan medoxomil (AZL), was determined spectrophotometrically and spectrofluorimetrically in its combination with chlorthalidone (CLT) in their combined dosage form. The UV-spectrophotometric technique depends on simultaneous measurement of the first derivative spectra for AZL and CLT at 286 and 257 nm, respectively, in methanol. The spectrofluorimetric technique depends on measurement of the fourth derivative of the synchronous spectra intensities of AZL in presence of CLT at 298 nm in methanol. The effects of different solvents on spectrophotometric and spectrofluorimetric responses were studied. For, the spectrofluorimetric study, the effect of pH and micelle-assisted fluorescence enhancement were also studied. Linearity, accuracy, and precision were found to be satisfactory over the concentration ranges of 8-50 µg mL(-1) and 2-20 µg mL(-1) for AZL and CLT, respectively, in the spectrophotometric method as well as 0.01-0.08 µg mL(-1) for AZL in the spectrofluorimetric method. The methods were successfully applied for the determination of the studied drugs in their co-formulated tablets. The developed methods are inexpensive and simple for the quality control and routine analysis of the cited drugs in bulk and in pharmaceuticals.

Steady-state and synchronous spectrofluorimetric methods for simultaneous determination of aliskiren hemifumarate and amlodipine besylate in dosage forms.

Aliskiren hemifumarate (ALS) and amlodipine besylate (AML) were simultaneously determined by two different spectrofluorimetric techniques. The first technique depends on direct measurement of the steady-state fluorescence intensities of ALS and AML at 313 nm and 452 nm upon excitation at 290 and 375 nm, respectively, in a solvent composed of methanol and water (10: 90, v/v). The second technique utilizes synchronous fluorimetric quantitative screening of the emission spectra of ALS and AML at 272 and 366 nm, respectively using Δλ of 97 nm. Effects of different solvents and surfactants on relative fluorescence intensity were studied. The method was validated according to ICH guidelines. Linearity, accuracy and precision were found to be satisfactory in both techniques over the concentration ranges of 1-15 and 0.4-4 µg/mL for ALS and AML, respectively. In the first technique, limit of detection and limit of quantification were estimated and found to be 0.256 and 0.776 µg/mL for ALS as well as 0.067 and 0.204 µg/mL for AML, respectively. Also, limit of detection and limit of quantification were calculated in the synchronous method and found to be 0.293 and 0.887 µg/mL for ALS as well as 0.034 and 0.103 µg/mL for AML, respectively. The methods were successfully applied for the determination of the two drugs in their co-formulated tablets. The results were compared statistically with reference methods and no significant difference was found. The developed methods are rapid, sensitive, inexpensive and accurate for the quality control and routine analysis of the cited drugs in bulk and in pharmaceutical preparations without pre-separation.

Synchronized separation of seven medications representing most commonly prescribed antihypertensive classes by using reversed-phase liquid chromatography: Application for analysis in their combined formulations.

A reversed-phase high-performance liquid chromatography method was developed for the simultaneous determination of the diuretic, hydrochlorothiazide, along with six drugs representing the most commonly prescribed antihypertensive pharmacological classes such as atenolol, a selective ß1 blocker, amlodipine besylate, a calcium channel blocker, moexipril hydrochloride, an angiotensin-converting-enzyme inhibitor, valsartan and candesartan cilexetil, which are angiotensin II receptor blockers, and aliskiren hemifumarate, a renin inhibitor, using irbesartan as an internal standard. The chromatographic separation was achieved using acetonitrile/sodium phosphate dibasic buffer (0.02 M, pH 5.5) at a flow rate of 1 mL/min in gradient elution mode at ambient temperature on a stationary phase composed of an Eclipse XDB-C18 (4.6 × 150 mm, 5 µm) column. UV detection was carried out at 220 nm. The method was validated according to ICH guidelines. Linearity, accuracy, and precision were satisfactory over the concentration ranges of 2-40 µg/mL for hydrochlorothiazide and candesartan cilexetil, 20-120, 10-160, 5-40, 20-250, and 5-50 µg/mL for atenolol, valsartan, moexipril hydrochloride, aliskiren hemifumarate, and amlodipine besylate, respectively. The method was successfully applied for the determination of each of the studied drugs in their combined formulations with hydrochlorothiazide. The developed method is suitable for the quality control and routine analysis of the cited drugs in their pharmaceutical dosage forms.

LC-MS-MS simultaneous determination of atorvastatin and ezetimibe in human plasma.

Atorvastatin and ezetimibe are lipid-lowering drugs prescribed for the treatment of hypercholesterolemia. An LC-MS-MS method has been developed and validated for the simultaneous estimation of atorvastatin and ezetimibe in human plasma using pitavastatin as an internal standard. Liquid-liquid extraction was used for the purification and preconcentration of analytes from human plasma matrix. The chromatographic separation was achieved within 3.0 min by an isocratic mobile phase consisting of 0.2% formic acid in water-acetonitrile (30:70, v/v), flowing through Agilent Eclipse-plus C18, 100 × 4.6 mm, 3.5 µm analytical column, at a flow rate of 0.6 mL min(-1). Multiple reaction monitoring transitions were measured in the positive ion mode for atorvastatin and internal standard, while ezetimibe was measured in negative ion mode. A detailed validation of the method was performed as per US-FDA guidelines and the standard curves were found to be linear in the range of 0.2-30.0 ng mL(-1) with a mean correlation coefficient >0.999 for both drugs. In human plasma, atorvastatin and ezetimibe were stable for at least 36 days at -70 ± 5 °C and 6 h at ambient temperature. After extraction from plasma, the reconstituted samples of atorvastatin and ezetimibe were stable in an autosampler at ambient temperature for 6 h. Also, the cited drugs were stable in plasma samples upon subjecting to three freeze thaw cycles. The method is simple, specific, sensitive, precise, accurate and suitable for bioequivalence and pharmacokinetic studies of this combination.

Spectrophotometric Methods for the Determination of Linagliptin in Binary Mixture with Metformin Hydrochloride and Simultaneous Determination of Linagliptin and Metformin Hydrochloride using High Performance Liquid Chromatography.

Simple, accurate and precise Zero order, first derivative spectrophotometric and chromatographic methods have been developed and validated for the determination of linagliptin (LNG) and metformin HCl (MET). The zero order and first derivative spectrophotometric methods were used for the determination of LNG in the range of 5-30 µg mL(-1) by measuring the absorbance at 299 nm and 311 respectively. Besides, a reversed-phase liquid chromatographic (RP-LC) method is described for the simultaneous determination of LNG and MET. Chromatographic separation was achieved on a Symmetry(®) Waters C18 column (150 mm × 4.6 mm, 5 µm). Isocratic elution based on potassium dihydrogen phosphate buffer pH (4.6) - methanol (30:70, v/v) at a flow rate of 1 mLmin(-1) with UV detection at 260 nm was performed. Linearity, accuracy and precision were found to be acceptable over the concentration ranges of 0.125-4 µg mL(-1) and 20-800 µg mL(-1) for LNG and MET, respectively. The results were statistically compared using one-way analysis of variance (ANOVA). The optimized methods were validated and proved to be specific, robust, precise and accurate for the quality control of the drugs in their pharmaceutical preparation.

Two chromatographic methods for the determination of some antimigraine drugs.

Two stability indicating chromatographic methods were proposed for the determination of almotriptan, eletriptan, and rizatriptan, in presence of their acid degradation products. The first method is a quantitative densitometric thin layer chromatography. The developing systems were; acetonitrile: methanol: dichloromethane: ammonia (10:6:3:1 v/v), ethyl acetate: methanol: ammonia (15:4:1 v/v), and methanol: acetonitrile: ammonia (9:4:1 v/v) for almotriptan, eletriptan and rizatriptan respectively. The TLC plates were scanned at 235 nm. Linear relationships were obtained over concentration ranges (5-50 µg/spot) for almotriptan and rizatriptan, and (5-60 µg/spot) for eletriptan. The second method based on the separation and determination of the studied drugs, using RP-HPLC technique. The separation was achieved on C18 Hypersil column, elution was carried out using phosphate buffer pH 3: methanol: acetonitrile (2: 1:1 v/v) at flow rate 2 mL/min and UV detection at 235 nm. Linear relationships were obtained over concentration ranges (10-200 µg/mL) for almotriptan and eletriptan, and (10-180 µg/mL) for rizatriptan. The chromatographic methods were successfully applied for the determination of each of the studied drugs in pure form, tablet form, and in laboratory prepared mixtures with their acid degradation products.

Spectrophotometric methods based on charge transfer complexation reactions for the determination of saxagliptin in bulk and pharmaceutical preparation.

Simple, accurate and precise spectrophotometric methods have been developed for the determination of saxagliptin in bulk and dosage forms. The proposed methods are based on the charge transfer complexes of saxagliptin with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). All the variables were studied to optimize the reactions' conditions. Beer's law was obeyed in the concentration ranges of 50-300 µg/ml and 10-110 µg/ml with DDQ and TCNQ, respectively. The developed methods were validated and proved to be precise and accurate for the quality control of the saxagliptinin its pharmaceutical dosage form.

Liquid chromatographic determination of linagliptin in bulk, in plasma and in its pharmaceutical preparation.

In this work, two reversed-phase liquid chromatographic (RP-LC) methods have been developed for the determination of linagliptin (LNG) based on isocratic elution using a mobile phase consisting of potassium dihydrogen phosphate buffer pH (4.6)-acetonitrile(20:80, v/v) at a flow rate of 1 mL min(-1). Two detection techniques have been applied either UV detection at 299 nm in the first method or fluorometric detection at 239 nm for excitation and 355 nm for emission in the second method. Chromatographic separation in the two methods was achieved on a Symmetry(®) cyanide column (150 mm × 4.6 mm, 5 µm). Linearity, accuracy and precision were found to be acceptable over the concentration ranges of 2.5-80 µg mL(-1) for LNG in bulk and 2.5-15 µg mL(-1) for LNG in plasma with the first method and 5-160 µg mL(-1) for LNG in bulk with the second method. The optimized methods were validated and proved to be specific, robust and accurate for the quality control of the cited drug in its pharmaceutical preparation.

Liquid chromatographic determination of alogliptin in bulk and in its pharmaceutical preparation.

In this work, a reversed-phase liquid chromatographic (RP-LC) method has been developed for the determination of alogliptin (ALG) based on isocratic elution using a mobile phase consisting of potassium dihydrogen phosphate buffer pH (4.6)-acetonitrile (20:80, v/v) at a flow rate of 1 mL min(-1) with UV detection at 215 nm. Chromatographic separation was achieved on a Symmetry(®) cyanide column (150 mm × 4.6 mm, 5 µm). Linearity, accuracy and precision were found to be acceptable over the concentration range of 5-160 µg mL(-1) for ALG in bulk. The optimized method was validated and proved to be specific, robust and accurate for the quality control of ALG in pharmaceutical preparations.

Liquid chromatographic determination of sitagliptin either alone or in ternary mixture with metformin and sitagliptin degradation product.

Two reversed-phase liquid chromatographic (RP-LC) methods have been developed for the determination of sitagliptin phosphate monohydrate (STG). The first method comprised the determination of STG alone in bulk and plasma; and in its pharmaceutical preparation. This method was based on isocratic elution of STG using a mobile phase consisting of potassium dihydrogen phosphate buffer pH (7.8)-acetonitrile (70:30, v/v) at a flow rate of 1 mL min(-1) with flourometric detection. The flourometric detector was operated at 267 nm for excitation and 575 nm for emission. In the second method, the simultaneous determination of STG and metformin (MET) in the presence of sitagliptin alkaline degradation product (SDP) has been developed. In this method, the ternary mixture of STG, MET and SDP was separated using a mobile phase consisting of potassium dihydrogen phosphate buffer pH (4.6)-acetonitrile-methanol (30:50:20, v/v/v) at a flow rate of 1 mL min(-1) with UV detection at 220 nm. Chromatographic separation in the two methods was achieved on a Symmetry(®) Waters C18 column (150 mm×4.6 mm, 5 µm). Linearity, accuracy and precision were found to be acceptable over the concentration ranges of 0.25-200 µg mL(-1) for STG with the first method and 5-160 µg mL(-1), 25-800 µg mL(-1) for STG and MET, respectively with the second method. The optimized methods were validated and proved to be specific, robust and accurate for the quality control of the cited drugs in pharmaceutical preparations.