Ionic-liquid based dispersive liquid-liquid microextraction followed by high performance liquid chromatographic determination of anti-hypertensives in rat serum.

A novel, simple and eco-friendly ionic liquid based dispersive liquid-liquid microextraction followed by HPLC determination of anti-hypertensive drugs viz., eprosartan, valasartan, irbesartan, losartan and telmisartan in rat serum has been developed and validated. Experimental parameters influencing the extraction efficiency, nature and volume of the ionic liquid, dispenser solvent, extraction time and effect of salt were optimized. Under the optimum conditions, the extraction recoveries were between 92.85 and 98.50%. The relative standard deviations of intra-and inter-day accuracy varied between 1.9 and 9.1% (n=3). The linearity of the proposed method was 0.1-20µg/mL with coefficients of determination varying between 0.9979 and 0.9992.

Liquid chromatography tandem mass spectrometric studies of indinavir sulphate and its forced degradation products.

Indinavir sulphate was subjected to forced degradation under hydrolysis (acidic, basic and neutral), oxidation, photolysis and thermal stress as prescribed by ICH guidelines. It was degraded under acidic, basic, neutral and oxidative stress conditions, while it was stable under other conditions. After degradation total eight degradation products were formed. The degradation products were identified and their separation was accomplished on Waters XTerra(®) C(18) column (250 mm × 4.6mm i.d., 5 µm) using 20mM ammonium actate:acetonitrile as (50:50, v/v) mobile phase in an isocratic elution mode by LC. The method was extended to LC-MS/MS for characterization of the degradation products and the fragmentation pathways were proposed. The proposed structures of degradation products were also confirmed by HRMS studies. No previous reports were found in the literature regarding the characterization of degradation products of indinavir sulphate.

Liquid chromatography-mass spectrometric determination of losartan and its active metabolite on dried blood spots.

A simple and rapid quantitative bioanalytical liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for simultaneous determination of losartan and its active metabolite, losartan carboxylic acid on rat dried blood spots was developed and validated as per regulatory guidelines. Losartan and its metabolite were extracted from dried blood spots using 50% aqueous methanol and separated on Waters XTerra(®) RP18 (250 mm × 4.6 mm, 5 µm) column using mobile phase composed of 40% acetonitrile and 60% aqueous ammonium acetate (10mM). The eluents were monitored using ESI tandem mass spectrometric detection with negative polarity in MRM mode using ion transitions m/z 421.2→179.0, m/z 435.3→157.0 and m/z 427.3→193.0 for losartan, losartan carboxylic acid and Irbesartan (internal standard), respectively. The method was validated over the linear range of 1-200 ng/mL and 5-1000 ng/mL with lower limits of quantification of 1.0 ng/mL and 5.0 ng/mL for losartan and losartan carboxylic acid, respectively. Inter and intra-day precision and accuracy (Bias) were below 5.96% and between -2.8 and 1.5%, respectively. The mean recoveries of the analytes from dried blood spots were between 89% and 97%. No significant carry over and matrix effects were observed. The stability of stock solution, whole blood, dried blood spot and processed samples were tested under different conditions and the results were found to be well within the acceptable limits. Additional validation parameters such as influence of hematocrit and spot volume were also evaluated and found to be well within the acceptable limits.

Identification and characterization of stressed degradation products of prulifloxacin using LC-ESI-MS/Q-TOF, MSn experiments: development of a validated specific stability-indicating LC-MS method.

A rapid, specific and novel gradient LC-MS method has been developed and validated for the identification and characterization of stressed degradation products (DPs) of prulifloxacin (PF) using liquid chromatography combined with quadrupole time-of-flight electrospray ionization tandem mass spectrometry (LC/Q-TOF-ESI-MS/MS). PF was subjected to hydrolytic (acidic, alkaline and neutral), oxidation, photolytic and thermal stress, as per ICH guidelines Q1A (R2). The drug showed extensive degradation in hydrolytic and oxidative, while it was stable to thermal and photolytic stress conditions. In total, 13 DPs were formed and the chromatographic separation of drug and its DPs was achieved on a C-18 column (4.6 × 250 mm, 5 µm) using gradient elution method. All the DPs have been identified and characterized using MS(n) experiments and accurate mass measurements. The LC-MS method was validated with respect to specificity, linearity, accuracy, precision and robustness.

Separation and characterization of forced degradation products of abacavir sulphate by LC-MS/MS.

Abacavir sulphate was subjected to forced degradation under the conditions of hydrolysis (acid, alkali and neutral), oxidation, photolysis and thermal stress as prescribed by ICH. Eight degradation products were formed and their separation was accomplished on Waters XTerra C18 (250 mm x 4.6 mm, 5 µm) column using 20 mM ammonium acetate:acetonitrile as a mobile phase in gradient elution mode by LC. The degradation products were characterized by LC-MS/MS and its fragmentation pathways were proposed. No previous reports were found in the literature regarding the degradation behavior of abacavir sulphate.

LC-MS/MS studies of ritonavir and its forced degradation products.

Forced degradation of ritonavir (RTV), under the conditions of hydrolysis (acidic, basic and neutral), oxidation, photolysis and thermal stress as prescribed by ICH was studied using LC-MS/MS. Eight degradation products were formed and their separation was accomplished on Waters XTerra C(18) column (250 mm x 4.6 mm i.d., 5 microm) using water:methanol:acetonitrile as (40:20:40, v/v/v) mobile phase in an isocratic elution mode by LC. The method was extended to LC-MS/MS for characterization of the degradation products and the pathways of decomposition were proposed. No previous reports were found in the literature regarding the characterization of degradation products of ritonavir.