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.

Continuously rejuvenated ion exchanger

Abstract: An apparatus for ion exchange which comprises (1) a very small diameter helix shaped inner tube of a suitable ion exchanging material having a filament therein and having its terminal ends inserted into entry and exit tubes, and (2) a diametrically slightly larger and longer length hollow outer tube having (a) the helix enclosed therein; (b) inlet and outlet apertures; and (c) sealed ends around the entry and exit tubes leading to the helix, and the method of making and using the same.

Resolving DNA in free solution

Abstract: DNA molecules are usually separated by gel electrophoresis. While gels help resolve DNA, the polymers bring problems to the analysis (e.g., difficulty in automating and poor reproducibility). One way to eliminate these problems completely is to separate DNA in free solutions. However, DNA fragments cannot normally be resolved in a free solution by electrophoresis because the electrophoretic mobilities of these molecules have similar charge-to-mass ratios, especially when the fragments are large. Efforts have been invested in free-solution DNA separations and a number of approaches (e.g., high-performance liquid chromatography, end-labeled free-solution electrophoresis, entropic traps, and DNA prism) have been successfully developed. Very recently, a new technique, called bare narrow capillary-open tubular chromatography (BaNC-OTC), was developed and can resolve a wide range of sizes of DNA in a few minutes. In this article, we review the significant progress on free-solution DNA separations, with emphasis on the most recent, advanced developments.

Measurement of Carbonyl Compounds as the 2,4-Dinitrophenylhydrazonate Anion. Reaction Mechanism and an Automated Measurement System

Abstract: The standard procedure for determining carbonyl compounds involves the addition of strong caustic alkali to 2,4-dinitrophenylhydrazones formed upon the reaction of carbonyl compounds with 2,4-dinitrophenylhydrazine (DNPH) 1 In strong base, the hydrazones form a dark red anion of quinonoid structure, 2 while the corresponding product from the unreacted DNPH decomposes rapidly, resulting in a low blank The mechanism of this decomposition has never been clearly understood In this work, we describe a photometric flow injection analyzer for the automated measurement of the carbonyl content of alcohol ethoxylate samples A detailed study of the mechanism of the alkatine decomposition is reported

Functionalized Cycloolefin Polymer Capillaries for Open Tubular Ion Chromatography

Abstract: We describe novel cycloolefin polymer (COP)-based open tubular capillary ion exchange columns. COP capillaries (inner diameter of 19–28 μm) were successfully sulfonated at room temperature using a cocktail of ClSO3H (85–95% w/w) and HOAc or H2SO4. The cation exchange capacity is controlled by the sulfonation time and the sulfonation solution composition and can be as high as 300 pequiv/mm2. Following sulfonation, the capillaries were coated with 65-nm-diameter anion exchanger (AEX) latex nanoparticles that attach electrostatically. The typical anion exchange capacities were ∼20 pequiv/mm2. The chromatographic behavior of the AEX latex-coated COP capillaries are greatly dependent on the degree of sulfonation. When the base is heavily sulfonated, neutrals elute after the anions. The position of the water dip varies with the degree of sulfonation; the elution order is normal (water dip appear before anions) only with lightly sulfonated columns. On silica (−SiOH) or poly(methyl methacrylate) (−COOH) surfaces,...

Annular dual membrane permselective device and method

Abstract: A permselective assembly for the selective transport of a species of interest across a semipermeable ion, exchange barrier and a method of operating the same are disclosed. The assembly includes an inner tube of a permselective material disposed within the inner volume of an outer tube of a permselective material forming an annular channel therebetween. This annular dual tube arrangement decreased the hold up volume of the outer tube and increases efficiency of transport of the species of interest.

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...