Development and validation of liquid chromatography-tandem mass spectrometric method for the quantification of ciprofibrate from human plasma.

A new rapid, selective and sensitive liquid chromatography-tandem mass spectrometric method was developed and validated for the determination of ciprofibrate, an antihyperlipidemic agent, in K2EDTA human plasma. Furosemide was used as internal standard (IS). The ciprofibrate and IS were extracted using Oasis HLB 1 cc 30 mg solid-phase extraction cartridge. The chromatographic separation was performed on ACE C18, 50 × 4.6 mm, 5 µm column. The mobile phase consisted of 0.001% ammonia in methanol-acetonitrile-water (70:20:10, v/v/v). Detection and quantitation were performed by a triple quadrupole equipped with electrospray ionization and multiple reaction monitoring in negative ionization mode. The most intense [M-H](-) transition for ciprofibrate at m/z 287.0 → 85.0 and for IS at m/z 328.9.0 → 204.9 were used for quantification. The method was found to linear over the range of 25-30,000 ng/mL (r > 0.998). The lower limit of quantitation (LLOQ) was 25 ng/mL. The extraction recovery was above 90%. The accuracy was found to be 101.26-106.44%. The stability testing was also investigated and it was found that both drug and IS were quite stable. The developed method was successfully applied to the bioequivalence study of ciprofibrate 100 mg tablet after oral administration to healthy human volunteers.

Stability indicating LC-method for estimation of paracetamol and lornoxicam in combined dosage form.

A simple, specific and stability indicating reversed phase high performance liquid chromatographic method was developed for the simultaneous determination of paracetamol and lornoxicam in tablet dosage form. A Brownlee C-18, 5 µm column having 250×4.6 mm i.d. in isocratic mode, with mobile phase containing 0.05 M potassium dihydrogen phosphate:methanol (40:60, v/v) was used. The flow rate was 1.0 ml/min and effluents were monitored at 266 nm. The retention times of paracetamol and lornoxicam were 2.7 min and 5.1 min, respectively. The linearity for paracetamol and lornoxicam were in the range of 5-200 µg/ml and 0.08-20 µg/ml, respectively. Paracetamol and lornoxicam stock solutions were subjected to acid and alkali hydrolysis, chemical oxidation and dry heat degradation. The proposed method was validated and successfully applied to the estimation of paracetamol and lornoxicam in combined tablet dosage form.

Development and validation of a stability-indicating RP-HPLC method for duloxetine hydrochloride in its bulk and tablet dosage form.

The objective of the present work was to develop a stability-indicating RP-HPLC method for duloxetine hydrochloride (DUL) in the presence of its degradation products generated from forced decomposition studies. The drug substance was found to be susceptible to stress conditions of acid hydrolysis. The drug was found to be stable to dry heat, photodegradation, oxidation and basic condition attempted. Successful separation of the drug from the degradation products formed under acidic stress conditions was achieved on a Hypersil C-18 column (250 mm à 4.6 mm id, 5Îm particle size) using acetonitrile: 0.01 M potassium dihydrogen phosphate buffer (pH 5.4 adjusted with orthophosphoric acid) (50:50, v/v) as the mobile phase at a flow rate of 1.0 ml/min. Quantification was achieved with photodiode array detection at 229 nm over the concentration range 1â25 Îg/ml with range of recovery 99.8â101.3 % for DUL by the RP-HPLC method. Statistical analysis proved the method to be repeatable, specific, and accurate for estimation of DUL. It can be used as a stability-indicating method due to its effective separation of the drug from its degradation products.

Determination of nebivolol hydrochloride and hydrochlorothiazide in tablets by first-order derivative spectrophotometry and liquid chromatography.

Two simple and accurate methods for analysis of nebivolol hydrochloride (NEB) and hydrochlorothiazide (HCTZ) in their combined dosage forms were developed using first-order derivative spectrophotometry and reversed-phase liquid chromatography (LC). NEB and HCTZ in their combined dosage forms (tablets) were quantified using first-derivative responses at 294.6 and 334.6 nm in the spectra of their solutions in methanol. The calibration curves were linear in the concentration range of 8-40 microg/mL for NEB and 10-60 microg/mL for HCTZ. LC analysis was performed on a Phenomenex Gemini C18 column (250 x 4.6 mm id, 5 microm particle size) in the isocratic mode with 0.05 M potassium dihydrogen phosphate-acetonitrile-methanol (30 + 20 + 50, v/v/v; pH 4) mobile phase at a flow rate of 1 mL/min. Detection was made at 220 nm. Both of the drugs and the internal standard (ezetimibe) were well resolved with retention times of 5.1 min for NEB, 2.9 min for HCTZ, and 8.2 min for ezetimibe. The calibration curves were linear in the concentration range of 1-14 microg/mL for NEB and 0.3-28 microg/mL for HCTZ. Both methods were validated and found to be accurate, precise, and specific, and results were compared statistically. Developed methods were successfully applied for the estimation of NEB and HCTZ in their combined dosage forms.