High-throughput quantification of perindopril in human plasma by liquid chromatography/tandem mass spectrometry: application to a bioequivalence study

A simple, sensitive and rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of perindopril in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by mass spectrometry in the multiple reaction monitoring mode using the respective [M+H](+) ions, m/z 369/172 for perindopril and m/z 417/234 for the internal standard. The method exhibited a linear dynamic range of 0.1-100 ng/mL for perindopril in human plasma. The lower limit of quantification was 0.1 ng/mL with a relative standard deviation of less than 6.1%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 450 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability and bioequivalence studies.     

Development of a validated high-throughput LC-ESI-MS method for determination of sirolimus on dried blood spots

A high‐throughput liquid chromatography–electrospray ionization mass spectrometric (LC–ESI‐MS) method for screening of sirolimus on dried blood spots (DBS) was developed and validated. It involves solvent extraction of a punch of DBS followed by reversed‐phase LC on a relatively new monolithic column consisting of a silica rod with bimodal pore structure and detection by ESI‐MS. The run time was less than 3 min with a very low backpressure at a flow rate of 0.5 mL/min. The method can analyze more than 100 samples in an 8 h working day, including sample preparation. The assay was linear from 1 to 100 ng/mL. The mean recovery was 92.42%. The mean inter‐day and intra‐day precisions were 1.23 and 1.41%, respectively. The developed method is simple, rapid and useful for clinical applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis, characterisation and catalytic potential of hydrazonato-vanadium(V) model complexes with [VO]3+ and [VO2]+ cores

Reaction between [VO(acac)2] and H2L (H2L are the hydrazones H2sal-nah I or H2sal-fah II; sal = salicylaldehyde, nah = nicotinic acid hydrazide and fah = 2-furoic acid hydrazide) in methanol leads to the formation of oxovanadium(IV) complexes [VOL.H2O](H2L = I: 1, H2L = II: 4). Aerial oxidation of the methanolic solutions of 1 and 4 yields the dinuclear oxo-bridged monooxovanadium(V) complexes [{VOL}2mu-O](H2L = I: 2, H2L = II: 5). These dinuclear complexes slowly convert, in excess methanol, to [VO(OMe)(MeOH)L](H(2)L = I: 9, H(2)L = II: 10), the crystal and molecular structures of which have been determined, confirming the ONO binding mode of the dianionic ligands in their enolate form. Reaction of aqueous K[VO3] with the ligands at pH ca. 7.5 results in the formation of [K(H2O)][VO2L](H2L = I: 3, H2L = II: 6). Treatment of 3 and 6 with H2O2 yields (unstable) oxoperoxovanadium(v) complexes K[VO(O2)L], the formation of which has been monitored spectrophotometrically. Acidification of methanolic solutions of 3 and 6 with HCl affords oxohydroxo complexes, while the neutral complexes [VO2(Hsal-nah)] 7 and [VO2(Hsal-fah)] 8 were isolated on treatment of aqueous solutions of 3 and 6 with HClO4. These complexes slowly transform into 9 and 10 in methanol, as confirmed by 1H, 13C and 51V NMR. The anionic complexes 3 and 6 catalyse the oxidative bromination of salicylaldehyde in water in the presence of H2O2/KBr to 5-bromosalicylaldehyde and 3,5-dibromosalicylaldehyde, a reaction similar to that exhibited by vanadate-dependent haloperoxidases. They are also catalytically active for the oxidation of benzene to phenol and phenol to catechol and p-hydroquinone.     

Engineered Nanomaterial Assisted Signal‐amplification Strategies for Enhancing Analytical Performance of Electrochemical Biosensors

The design and development of modern biosensors for sensitive and selective detection of various biomarkers is important in diversified arenas including healthcare, environment, and food industries etc. The requirement of more robust and reliant biosensors lead to the development of various sensing modules. The nanomaterials having specific optical, electrical, and mechanical strength can pave the way towards development of ultrafast, robust, and miniaturized modules for biosensors. It can provide not only the point‐of‐care applicability but also has tremendous commercial as well as industrial justification. In order to improve the performance of the sensor systems, various nanostructure materials have been readily studied and applied for development of novel biosensors. In the last few years, researchers are engaged on harnessing the unique atomic and molecular properties of advance‐engineered materials including carbon nanotubes, graphene nanosheets, metal nanoparticles, metal oxide nanoparticles, and their nano‐conjugates. In view of such recent developments in nanomaterial engineering, the current review has been formulated emphasizing the role of these materials in surface engineering, biomolecule conjugation, and signal amplification for development of various ultrasensitive and robust biosensors having commercial as well as industrial viability. Attention is given on the electrochemical biosensors incorporating various nanomaterials and their conjugates. Importance of nanomaterials in the analytical performance of the various biosensor has also been discussed. To put a perceptive insights on the importance of various nanomaterials, an extended table is incorporated, which includes probe design, analyte, LOD, and dynamic range of various electrochemical biosensors.     

Chemical constituents of Bacopa procumbens

Phytochemical investigation of Bacopa procumbens afforded two new phenolic glycosides 1 and 2, for the first time, along with 12 known compounds 3-14. Structures of these compounds were established based on spectral and chemical evidences.     

Studies on the structural,thermal and optical behaviour of solution grown organic NLO material: 8‐hydroxyquinoline

Single crystal of 8‐hydroxyquinoline (8HQ) having chemical formula C₉H₇NO, an organic nonlinear optical (NLO) material has been successfully grown by slow evaporation solution growth technique at room temperature. The crystal system has been confirmed from the powder X‐ray diffraction (PXRD) analysis. The crystalline perfection was evaluated by high resolution X‐ray diffractometry (HRXRD). From this analysis we found that the quality of the crystal is quite good. However, a very low angle (tilt angle 14 arc sec) boundary was observed which might be due to entrapping of solvent molecules in the crystal during growth. Its optical behavior has been examined by UV‐Vis. analysis, which shows the absence of absorbance between the wavelengths ranging from 400 to 1200 nm. From the thermal analysis it was observed that the material exhibits single sharp weight loss starting at 113°C without any degradation. The laser damage threshold was measured at single shot mode and the SHG behavior has been tested using Nd:YAG laser as a source. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Rapid determination of rifaximin on dried blood spots by LC‐ESI‐MS

The use of blood spot collection cards is a simple way to obtain specimens for therapeutic drug monitoring, assessing adherence to medications and preventing toxicity in a clinical setting. A high‐throughput liquid chromatography–electrospray ionization mass spectrometric (LC‐ESI‐MS) method for determination of rifaximin on dried blood spots (DBS) was developed and validated. It involves solvent extraction of a punch of DBS followed by reversed‐phase LC on a monolithic column consisting of a silica rod with bimodal pore structure and detection by ESI‐MS. Rifampicin was used as an internal standard (IS). The run time was within 5.0 min with a very low back‐pressure at a flow rate of 0.5 mL/min. The assay was linear from 0.1 to 10 ng/mL. The mean recovery was 98.42%. The developed method is very simple, rapid and useful for clinical applications. Copyright © 2011 John Wiley & Sons, Ltd.