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.

Fluorometric measurement of aqueous ammonium ion in a flow injection system

Abstract: An automated flow-injection method for NH/sub 3//NH/sub 4//sup +/ involving the ternary reaction of the analyte with o-phthaldialdehyde (OPA) and sulfite is described. The use of malodorous thiol compounds is avoided and the reaction provides much greater sensitivity by either fluorescence (detection limit 300 fmol or 20 nM NH/sub 4//sup +/) or absorption detection compared to the reaction involving 2-mercaptoethanol. The reaction shows considerable selectivity for ammonia over amino acids by a factor of 16 to > 500 for 11 common amino acids studied. The throughput rate is 25 samples/h.

Perchlorate in Milk

Abstract: Perchlorate was unambiguously detected by ion chro matography-suppressed conductivity (IC-CD) and/or ion chromatography−electrospray mass spectrometry (IC-MS) in seven of seven supermarket milk samples bought randomly in Lubbock, TX. Quantitation by IC-MS and IC-suppressed conductivity detection in conjunction with a preconcentration-preelution method provided comparable results. With a sample cleanup procedure that involved protein removal by ethanol and sequential passage though activated alumina and C-18 silica, the limit of detection for perchlorate in milk was 0.5 μg/L. The levels found ranged from 1.7 to 6.4 μg/L. An evaporated milk sample contained perchlorate at 1.1 ± 0.6 μg/L level, while we did not find detectable levels in a reconstituted powdered milk sample.

Determination of atmospheric sulfur dioxide without tetrachloromercurate(II) and the mechanism of the Schiff reaction

Abstract: Formaldehyde (7 mM) buffered at pH approx. 4 is used to stabilize atmospheric SO/sub 2/ as hydroxymethanesulfonic acid. Equilbrium data for the above reaction are presented. Sulfite, liberated from the compound by base, is added to acidic pararosaniline for color development by the Schiff reaction, and absorbance is measured at 580 nm. The procedure has been optimized with regard to acidity and reagent concentrations. The method is comparable to the West-Gaeke method in absorption and recovery efficiency, sensitivity, and precision. No unusual interferences are observed due to O/sub 3/, NO/sub 2/, and transition-metal ions, except Mn(II). A novel ion chromatographic procedure to determine hydroxymethanesulfonate and sulfate in the same sample is also described. Enhancement of sensitivity in the colorimetric method by solvent extraction has been studied. Investigations into the mechanism of the Schiff reaction and structure of the products have established the validity of the alkylsulfonic acid theory. Mechanistically an aminocarbinol seems to be the first intermediate, which undergoes subsequent nucleophillic substitution by bisulfite ion. To account for the high absorptivity of the product, we suggest that the sulfonic acid group is significantly ionized.

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...