Synchronized separation of atorvastatin—an antihyperlipidemic drug with antihypertensive, antidiabetic, antithrombotic drugs by RP-LC for determination in combined formulations

AbstractA new rapid and sensitive high performance liquid chromatography (HPLC) method has been developed for the simultaneous determination of atorvastatin—an antihyperlipidemic drug along with most commonly prescribed drugs (antihyperlipidemic, antihypertensive, antidiabetic, antithrombotic) in bulk and marketed combined formulations. The chromatographic separation was carried out by gradient elution mode with acetonitrile as organic modifier and 0.1% triethylamine acetate (TEAA) buffer pH 5 at a flow rate of 1mL/min and a diode array detector at wavelength 230nm was employed for detection of the analytes. Calibration curves were linear in the range of 5–150μg/mL for all the drugs with correlation coefficients of determination (r2 values)≥0.999. Limits of detection (LODs) and Limits of quantification (LOQs) ranged from 0.1 to 0.27μg/mL and 0.3 to 0.89μg/mL respectively. Intra-day and inter-day precision was studied at three concentration levels (20, 60 and 100μg/mL). The intra-day and inter-day RSD for all compounds was less than 2.0%. The accuracy for all compounds was found to be between 98% and 102%. Thus, the performance of the method described allows its use in quantification of atorvastatin along with 9 most commonly prescribed drugs available in market as atorvastatin combined dosage forms

Interaction of Pyrrolobenzodiazepine (PBD) Ligands with Parallel Intermolecular G-Quadruplex Complex Using Spectroscopy and ESI-MS

Studies on ligand interaction with quadruplex DNA, and their role in stabilizing the complex at concentration prevailing under physiological condition, has attained high interest. Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the interaction of PBD and TMPyP4 ligands, stoichiometry and selectivity to G-quadruplex DNA. Two synthetic ligands from PBD family, namely pyrene-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid (PBD1), mixed imine-amide pyrrolobenzodiazepine dimer (PBD2) and 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP4) were studied. G-rich single-stranded oligonucleotide d(5′GGGGTTGGGG3′) designated as d(T2G8), from the telomeric region of Tetrahymena Glaucoma, was considered for the interaction with ligands. ESI-MS and spectroscopic methods viz., circular dichroism (CD), UV-Visible, and fluorescence were employed to investigate the G-quadruplex structures formed by d(T2G8) sequence and its interaction with PBD and TMPyP4 ligands. From ESI-MS spectra, it is evident that the majority of quadruplexes exist as d(T2G8)2 and d(T2G8)4 forms possessing two to ten cations in the centre, thereby stabilizing the complex. CD band of PBD1 and PBD2 showed hypo and hyperchromicity, on interaction with quadruplex DNA, indicating unfolding and stabilization of quadruplex DNA complex, respectively. UV-Visible and fluorescence experiments suggest that PBD1 bind externally where as PBD2 intercalate moderately and bind externally to G-quadruplex DNA. Further, melting experiments using SYBR Green indicate that PBD1 unfolds and PBD2 stabilizes the G-quadruplex complex. ITC experiments using d(T2G8) quadruplex with PBD ligands reveal that PBD1 and PBD2 prefer external/loop binding and external/intercalative binding to quadruplex DNA, respectively. From experimental results it is clear that the interaction of PBD2 and TMPyP4 impart higher stability to the quadruplex complex

Generation and identification of ionic and neutral dithioformic acid [HC(S)SH]<SUP>·+/o</SUP>, dimercaptocarbene [HSCSH]<SUP>·+/o</SUP>, and dithiirane [H<SUB>2</SUB>C(S<SUB>2</SUB>)]<SUP>·+/o</SUP>: a neutralization-reionization mass spectrometry and theoretical study

Results of tandem mass spectrometric experiments characterize both ionic and neutral dithioformic acid a, dimercaptocarbene b, and dithiirane c in the gas phase. Observed collisional activation spectra of the ion at m/z 78 from compounds ethyl carbamoylmethane dithioate 1, 5-amino-1,3,4-thiadiazole-2-thiol 2, and rhodanine 3 and 1,2-dithiacyclopentane 4 are most compatible with the connectivities a, b, and c, respectively. The NRMS experiments on these structurally characterized ions reveal that the neutral dithioformic acid a, dimercaptocarbene b, and dithiirane c are viable species in the gas phase. Relative energies of the CH2S2 isomers and their radical cations calculated at the B3LYP/6-31G** level support these experimental observations. Comparisons are made between the relative energies of the oxygen and sulfur analogues. The high relative energy of dioxirane g in relation to dithiirane c makes the former a difficult target for experimental observation

Towards Detection of a Long-lived Protonated Metal Cation: Generation of GeH2+ Using High-Energy Collisions

A minimal lifetime of microseconds is displayed by the dication GeH2+, which has been detected for the first time as the product of charge-stripping experiments at 8 kV involving [GeH2]+ and O2. Coupled-cluster calculations suggest that XH2+ (X = Si, Ge

Selective separation, detection of zotepine and mass spectral characterization of degradants by LCâMS/MS/QTOF

A simple, precise, accurate stability-indicating gradient reversed-phase high-performance liquid chromatographic (RPâHPLC) method was developed for the quantitative determination of zotepine (ZTP) in bulk and pharmaceutical dosage forms in the presence of its degradation products (DPs). The method was developed using Phenomenex C18 column (250 mmÃ4.6 mm i.d., 5 µm) with a mobile phase containing a gradient mixture of solvents, A (0.05% trifluoroacetic acid (TFA), pH=3.0) and B (acetonitrile). The eluted compounds were monitored at 254 nm; the run time was within 20.0 min, in which ZTP and its DPs were well separated, with a resolution of >1.5. The stress testing of ZTP was carried out under acidic, alkaline, neutral hydrolysis, oxidative, photolytic and thermal stress conditions. ZTP was found to degrade significantly in acidic, photolytic, thermal and oxidative stress conditions and remain stable in basic and neutral conditions. The developed method was validated with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness as per ICH guidelines. This method was also suitable for the assay determination of ZTP in pharmaceutical dosage forms. The DPs were characterized by LCâMS/MS and their fragmentation pathways were proposed. Keywords: Zotepine, Stability-indicating RPâHPLC method, Characterization, ESI-Q-TOF-MS, Bulk drugs and formulation

Generation and characterization of ionic and neutral dihydroxy boron B(OH)(2)(+/0) in the gas phase

The dicoordinated borinium ion, dihydroxyborinium, B(OH)(2)(+) is generated from methyl boronic acid CH3B(OH)(2) by dissociative electron ionization and its connectivity confirmed by collisional activation. Neutralization-reionization (NR) experiments on this ion indicate that the neutral B(OH)(2) radical is a viable species in the gas phase. Both vertical neutralization of B(OH)(2)(+) and reionization of B(OH)(2) in the NR experiment are, however, associated with particularly unfavorable Franck-Condon factors. The differences in adiabatic and vertical electron transfer behavior can be traced back to a particular pi stabilization of the cationic species compared to the sp(2)-type neutral radical. Thermochemical data on several neutral and cationic boron compounds are presented based on calculations performed at the G2 level of theory

Fluorescence emission titration results for binding of PBD1, PBD2, and TMPyP4 to d(T₂G₈) G-quadruplex.

<p>Fluorescence emission titration results for binding of PBD1, PBD2, and TMPyP4 to d(T₂G₈) G-quadruplex.</p