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.

Electroosmosis: A reliable fluid propulsion system for flow injection analysis

Abstract: An electroosmosis based fluid propulsion system is described. The electroosmotic pump, operating in a high electric field, is isolated from other components by a grounding joint that is electrically conductive and permits the pumped fluid to be hydrodynamically coupled to contents downstream without leakage. The pump was used in single- and double-line flow injection analysis (FIA) systems. The determinations of chloride and iron(III) are discussed as representative examples. The experimental results shows excellent reproducibilities (relative standard deviation 0.4-0.8%), reflecting the stability and the reliability of the pump. The system can also be operated in a hybrid manner

Liquid Droplet. A Renewable Gas Sampling Interface

Abstract: As a gas stream flows across a liquid droplet, the soluble constituents contained in the gas diffuse to and dissolve in the liquid drop. From the viewpoint of analytical chemistry, this droplet is thus a potential sampling interface for such soluble constituents. The problem that needs to be solved relates to the manner of its incorporation in a chemical analysis system. This paper describes the coupling of this sampling interface with a sequential analysis system, demonstration of its applicability for the measurement of parts-per-billion levels of gaseous NH 3 , and a characterization of the performance of this experimental arrangement Various aspects of the behavior of the liquid droplet as a collection interface are theoretically discussed and experimentally examined using NH 3 and SO 2 as test gases.

Hematin as a peroxidase substitute in hydrogen peroxide determinations.

Abstract: Hematin can substitute for horseradish peroxidase (HRP) as the catalyst in the determination of hydrogen peroxide using phenolic substrates such as p-hydroxyphenylacetate or p-cresol. Although the peroxidatic activity of hematin from bovine blood is not as great as HRP in terms of unit iron content, the activity per unit weight is substantially greater. Hematin is 500 times less expensive than HRP per unit peroxidatic activity. In hematin-catalyzed systems, reaction development and fluorescence measurement can both be conducted optimally in the same ammoniacal buffer. Hydroxyalkyl hydroperoxides are rapidly hydrolyzed to H2O2 at this pH and are also determined. On the other hand, for methyl hydroperoxide, hematin exhibits only approximately 10% of the sensitivity exhibited by HRP. Hematin is significantly more stable in solution than HRP. The use of hematin as catalyst and p-cresol as the substrate leads to a particularly inexpensive and sensitive system, permitting a limit of detection (LOD) of 7 nM H2O2 in a flow-injection configuration.

Perchlorate in the United States. Analysis of relative source contributions to the food chain.

Abstract: Perchlorate has been considered by some a potential threat to human health, especially to developing infants and children because it may inhibit iodide uptake by the sodium iodide symporter (NIS) of the thyroid. In the United States, during the last several decades, environmental perchlorate has had three recognized sources stemming from (a) its use as an oxidizer (including in rocket propellants), (b) its presence in Chilean nitrate fertilizer (CNF), and (c) natural production. An analysis of the relative source strengths and how they may influence entry into the food chain has not been conducted. Averaged over the last ∼60 years, we estimate that the source strengths have been (a) 10.6, (b) 0.75, and (c) 0.13−0.64 Gg/y for the United States as a whole. Of this, while (b) and (c) represent actual dispersed amounts, the figure in (a) is the amount of perchlorate produced and only a fraction (f) of it has been dispersed and often in a more localized fashion. In addition, dispersal of (b) has taken place on...

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...