Puran Singhal

Bio: Puran Singhal is an academic researcher from Kadi Sarva Vishwavidyalaya. The author has contributed to research in topics: Selected reaction monitoring & Triple quadrupole mass spectrometer. The author has an hindex of 13, co-authored 37 publications receiving 417 citations.

Repeat Analysis and Incurred Sample Reanalysis: Recommendation for Best Practices and Harmonization from the Global Bioanalysis Consortium Harmonization Team

Abstract: The A7 harmonization team (A7 HT), a part of the Global Bioanalysis Consortium (GBC), focused on reviewing best practices for repeat analysis and incurred sample reanalysis (ISR) as applied during regulated bioanalysis. With international representation from Europe, Latin America, North America, and the Asia Pacific region, the team first collated common practices and guidance recommendations and assessed their suitability from both a scientific and logistical perspective. Subsequently, team members developed best practice recommendations and refined them through discussions and presentations with industry experts at scientific meetings. This review summarizes the team findings and best practice recommendations. The few topics where no consensus could be reached are also discussed. The A7 HT recommendations, together with those from the other GBC teams, provide the basis for future international harmonization of regulated bioanalytical practices.

Selective Determination of Antiretroviral Agents Tenofovir, Emtricitabine, and Lamivudine in Human Plasma by a LC-MS-MS Method for a Bioequivalence Study in Healthy Indian Subjects

Abstract: A selective, sensitive, rugged, and high throughput liquid chromatography tandem mass spectrometry method is developed for the determination of one nucleotide tenofovir (TFV) and two nucleosides emtricitabine (FTC) and lamivudine (3TC) reverse transcriptase inhibitors in human plasma. Plasma samples were prepared by solid-phase extraction of the analytes and acyclovir (ACV) as internal standard using Waters Oasis MCX cartridges. The chromatographic separation is achieved in a run-time of 3.0 min on an ACE 5 CN column (150 mm × 4.6 mm, 5 μm) under isocratic conditions. The mobile phase consisted of 0.5% formic acid in water and acetonitrile (55:45, v/v). The protonated precursor --> product ion transitions for TFV, FTC, 3TC, and internal standard were monitored on a triple quadrupole mass spectrometer operating in the multiple reaction monitoring (MRM) and positive ion mode. A linear dynamic range of 4.0-802 ng/mL, 15.0-3006 ng/mL, and 20.1-4023 ng/mL is established for TFV, FTC, and 3TC, respectively, using 0.2 mL plasma sample. The method is fully validated for its sensitivity, selectivity, accuracy and precision, ion suppression, matrix effect, recovery, stability, and dilution integrity. It is successfully applied to a bioequivalence study of [300(TFV) + 200(FTC) + 300(3TC)] mg tablet formulation in 43 healthy human subjects under fasting conditions.

Lactoferrin: Structure, function, denaturation and digestion

Abstract: Lactoferrin (LF) is a multifunctional protein occurring in many biological secretions including milk. It possesses iron binding/transferring, antibacterial, antiviral, antifungal, anti-inflammatory and anti-carcinogenic properties. These functional properties intimately depend on the structural integrity of LF especially its higher order conformation. LF is primarily extracted from bovine milk and it is subsequently added into many commercial products such as nutritional supplements, infant formula, cosmetics and toothpaste. LF is sensitive to denaturation induced by temperature and other physicochemical stresses. Hence, the extraction, powder formation processes of LF and processing parameters of LF-containing products have to be optimized to minimise its undesired denaturation. This review documents the advances made on structure-function relationships and discusses the effectiveness of methods used to preserve the structure of LF during thermal processing. Oral delivery, as the most convenient way for administering LF, is also discussed focusing on digestion of LF in oral, gastric and intestinal stages. The effectiveness of methods used to deliver LF to intestinal digestion stage in structurally intact form is also compared. Altogether, this work comprehensively reviews the fate of LF during thermal processing and digestion, and suggests suitable means to preserve its structural integrity and functional properties. Scope of review The manuscript aims at providing a comprehensive review of the latest publications on four aspects of LF: structural features, functional properties, nature and extent of denaturation and gastrointestinal digestion. It also analyses how these publications benefit food and pharmaceutical industries.

Coupling ultra-high-pressure liquid chromatography with mass spectrometry

Abstract: In recent years, different approaches have been taken to improve chromatographic performance in terms of analysis time and/or resolution. The use of columns packed with sub-2μm particles in ultra-high-pressure liquid chromatography (UHPLC) has become a technique of choice in many laboratories. Furthermore, for the analysis of complex matrices (e.g., biological fluids, plant extracts, and food and environmental samples), coupling UHPLC with mass spectrometry (MS) or tandem MS (MS 2 ) provides a powerful analytical tool. This review describes major advances in the field of UHPLC-MS and UHPLC-MS 2 . We strongly emphasize the possibility of speeding up bioanalysis, drug metabolism, and multi-residue screening assays, while maintaining qualitative and quantitative performance equivalent to HPLC-MS and HPLC-MS 2 . We also report the possibility of gaining additional information in metabolomics, using high-resolution UHPLC with a time-of-flight analyzer. The studies summarized are discussed in this review in terms of throughput increases and resolution enhancements afforded by UHPLC. In addition, we highlight the impact of UHPLC conditions on MS detection capabilities (e.g., acquisition rate, limits of detection and matrix effects).

Incurred sample reanalysis (ISR): a decisive tool in bioanalytical research

Abstract: The AAPS Workshop 2008 on Current Topics in GLP Bioanalysis: Assay Reproducibility for Incurred Samples was the defining moment in establishing incurred sample reanalysis (ISR) as a mandatory exercise in demonstrating assay reproducibility using incurred (study) samples. The importance of ISR can be envisaged from its role in clinical as well as non-clinical studies. Incurred samples can differ significantly in their composition when compared with the calibration standards and quality control samples that are used to validate the developed method. The present article attempts to summarize five troubleshooting cases encountered in the analyses of incurred samples for bioanalytical methods developed in our laboratory for mesalamine, hydrochlorothiazide, clopidogrel, sildenafil and rabeprazole. The issues identified were related to: sample inhomogeneity, sample processing error, impact of buffer pH during sample preparation, instability of metabolite and change in laboratory environment. The steps taken to trace and correct these incidents are discussed with adequate data. These examples will further broaden the scope and emphasize the significance of ISR. We believe this investigation will help to develop more reliable and efficient bioanalytical methods.