Purnendu K. Dasgupta

Bio: Purnendu K. Dasgupta is an academic researcher from University of Texas at Arlington. The author has contributed to research in topics: Ion chromatography & Detection limit. The author has an hindex of 62, co-authored 506 publications receiving 16779 citations. Previous affiliations of Purnendu K. Dasgupta include Dow Chemical Company & Texas Tech University.

Time-of-Sight Liquid Flow Measurements in the Low Nanoliters per Minute Scale.

Abstract: We describe an affordable and robust measurement technique applicable to nanoscale liquid flow. The approach can provide good precision (<1% RSD) in the 1.5-15 nL/min flow range. The motion of a conductive/nonconductive immiscible segmental interface in a capillary is followed by an admittance detector. The conductive marker segment, e.g., a salt solution, is protected on both sides from the principal flow stream by immiscible guard segments, typically a fluorocarbon (FC) liquid, of significantly greater impedance. Fluorosilylation of the capillary ensures no other liquid film between the FC segments and the wall (perfect piston). A given interface/marker can typically be used only once in interface/front tracking systems. We overcome this by putting the sensor capillary in a valved configuration where the flow direction in the sensor is reversed before the guard/marker segments escape. Several strategies are possible to interpret flow rate from the sensor output, including the rate of the interface movement. During the measurement process, a change in this rate of movement can be detected in <1 s. Small temperature variations in the 25-35 °C range did not affect sensor behavior.

Identification of ions in anion chromatography by stopped flow chronoamperometry

Abstract: L'identification des anions mineraux ou organiques est permise grâce a la connection en serie d'une valve trois voies et d'un detecteur de conductivite a courant continu apres le detecteur a impulsion d'un chromatographe ionique avec suppresseur d'eluant. Presentation et discussion des courbes de chronoamperometrie de divers ions (acetate, hexanesulfonate, phosphate, IO 3 − , ClO 4 − , SO 4 2− , S 2 O 6 2− )

Enhancement of Separation Efficiency in Capillary Electrophoresis by Electrostacking without Liquid Contact

Abstract: Quantitative reproducibility and separation efficiency in high-performance capillary electrophoresis is often limited by the reproducibility and the nature of the sample introduction procedure. This is particularly true where electrostacking is involved, whether such is deliberately carried out or happens automatically with the choice of ionic strength of the running electrolyte. Extraneous dispersion frequently originates in the act of sample introduction, for example, from the shock of the capillary entering a sample vial or a sample-filled capillary entering the carrier electrolyte source vial. A method based on the stacking of the sample constituents, before the capillary actually contacts the liquid in a vial, can reduce this problem. This technique can be utilized for the preconcentration of sample constituents and to improve separation efficiency by reducing dispersion. In favorable cases, plate counts can increase by as much as 160%, approaching theoretical diffusion-limited efficiencies.

Positive-signal indirect fluorometric detection in ion chromatography

Abstract: Possibilite d'une detection fluorimetrique indirecte pour des concentrations en ions eluants se situant dans la region d'auto-extinction

The origins and the future of microfluidics

Abstract: The manipulation of fluids in channels with dimensions of tens of micrometres--microfluidics--has emerged as a distinct new field. Microfluidics has the potential to influence subject areas from chemical synthesis and biological analysis to optics and information technology. But the field is still at an early stage of development. Even as the basic science and technological demonstrations develop, other problems must be addressed: choosing and focusing on initial applications, and developing strategies to complete the cycle of development, including commercialization. The solutions to these problems will require imagination and ingenuity.

Intrinsic peroxidase-like activity of ferromagnetic nanoparticles

Abstract: Nanoparticles containing magnetic materials, such as magnetite (Fe3O4), are particularly useful for imaging and separation techniques. As these nanoparticles are generally considered to be biologically and chemically inert, they are typically coated with metal catalysts, antibodies or enzymes to increase their functionality as separation agents. Here, we report that magnetite nanoparticles in fact possess an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, which are widely used to oxidize organic substrates in the treatment of wastewater or as detection tools. Based on this finding, we have developed a novel immunoassay in which antibody-modified magnetite nanoparticles provide three functions: capture, separation and detection. The stability, ease of production and versatility of these nanoparticles makes them a powerful tool for a wide range of potential applications in medicine, biotechnology and environmental chemistry.

Hormones and endocrine-disrupting chemicals: Low-dose effects and nonmonotonic dose responses

Abstract: For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from...

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

Abstract: Background: Thyroid disease in pregnancy is a common clinical problem. Since the guidelines for the management of these disorders by the American Thyroid Association (ATA) were first published in 2...