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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.


Papers
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TL;DR: In this paper, a month of semi-continuous and simultaneous measurements of particulate chloride and nitrate and gaseous HCl and HNO3 concentrations were made in the Tampa, Florida, as part of the Bay Region Atmospheric Chemistry Experiment (BRACE).

66 citations

Journal ArticleDOI
TL;DR: The ability of this approach to remove matrix interferences suggests that it would be also promising for perchlorate analysis in other challenging samples, and compares favorably with those from the currently recommended EPA Method.
Abstract: A simple, automated system for the determination of trace perchlorate by ion chromatography (IC) with an online preconcentration technique is reported. The sample is preconcentrated, and less strongly held ions preeluted before the analyte is transferred to the principal separation system. This approach provides low limits of detection (LOD) and is particularly robust toward the effect of high concentrations of common anions, such as those present in groundwater samples. It compares favorably with currently promulgated EPA method 314.0. The LOD (S/N = 3) is 0.77 μg/L for a 2-mL reagent water sample and decreases more-or-less proportionately with increasing sample volume, at least up to 20 mL. Even with a sample of conductivity 14.7 mS/cm (approximately that of 0.1 M Na2SO4), the recovery of added perchlorate at the 25.0 μg/L level was still 92%. The concentration of added perchlorate in the range of 1−400 μg/L was linearly correlated to the peak area, with an r2 value of 0.9997. The recovery of perchlorat...

65 citations

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TL;DR: A membrane-based electrochemical approach for the in situ production of ultrapure ionic substances has been developed with specific reference to the production of NaOH solutions and their use in ion chromatography.
Abstract: A membrane-based electrochemical approach for the in situ production of ultrapure ionic substances has been developed. This is illustrated with specific reference to the production of NaOH solutions and their use in ion chromatography. Two basic types of generators are described. In the first, a current-efficient single-membrane device generates a stream of NaOH and H 2 . This stream is degassed by a membrane-degasser en route to the chromatographic pump. In the second type, multiple membranes are used and the product NaOH channel does not contain gas. The product purity is excellent ― an electrodialytic membrane suppressor (EMS) produces a typical exchanged conductance of 340±40 nS/cm for 0-175 mM NaOH

63 citations

Journal ArticleDOI
01 Jun 1997-Talanta
TL;DR: A fluorometric technique based on a liquid drop excited from its interior by an optical fiber for the measurement of low concentrations of atmospheric hydrogen sulfide, which permits a simple fast inexpensive near real-time measurement with very little reagent consumption.

63 citations

Journal ArticleDOI
TL;DR: In this paper, the authors report on HCHO measurements in the Houston-Galveston Airshed (HGA) from summer 2006, showing that the HCHO/PAN ratios at the Moody Tower (MT) site close to downtown were dependent on the wind direction: southerly maritime winds brought in background levels (0.5-1 ppbv) while trajectories originating in the HSC resulted in high HCHO (up to 31.5 ppbV).
Abstract: . The Houston-Galveston Airshed (HGA) is one of the major metropolitan areas in the US that is classified as a nonattainment area of federal ozone standards. Formaldehyde (HCHO) is a key species in understanding ozone related air pollution; some of the highest HCHO concentrations in North America have been reported for the HGA. We report on HCHO measurements in the HGA from summer 2006. Among several sites, maximum HCHO mixing ratios were observed in the Houston Ship Channel (HSC), a region with a very high density of industrial/petrochemical operations. HCHO levels at the Moody Tower (MT) site close to downtown were dependent on the wind direction: southerly maritime winds brought in background levels (0.5–1 ppbv) while trajectories originating in the HSC resulted in high HCHO (up to 31.5 ppbv). Based on the best multiparametric linear regression model fit, the HCHO levels at the MT site can be accounted for as follows: 38.5±12.3% from primary vehicular emissions (using CO as an index of vehicular emission), 24.1±17.7% formed photochemically (using peroxyacetic nitric anhydride (PAN) as an index of photochemical activity) and 8.9±11.2% from industrial emissions (using SO2 as an index of industrial emissions). The balance 28.5±12.7% constituted the residual which cannot be easily ascribed to the above categories and/or which is transported into the HGA. The CO related HCHO fraction is dominant during the morning rush hour (06:00–09:00 h, all times are given in CDT); on a carbon basis, HCHO emissions are up to 0.7% of the CO emissions. The SO2 related HCHO fraction is significant between 09:00–12:00 h. After 12:00 h HCHO is largely formed through secondary processes. The HCHO/PAN ratios are dependent on the SO2 levels. The SO2 related HCHO fraction at the downtown site originates in the ship channel. Aside from traffic-related primary HCHO emissions, HCHO of industrial origin serves as an appreciable source for OH in the morning.

62 citations


Cited by
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Journal ArticleDOI
27 Jul 2006-Nature
TL;DR: The manipulation of fluids in channels with dimensions of tens of micrometres — microfluidics — has emerged as a distinct new field that has the potential to influence subject areas from chemical synthesis and biological analysis to optics and information technology.
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.

8,260 citations

Journal ArticleDOI
TL;DR: It is reported 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.
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.

4,500 citations

Journal ArticleDOI
TL;DR: The ability of DLLME technique in the extraction of other organic compounds such as organochlorine pesticides, organophosphorus pesticides and substituted benzene compounds were studied.

2,959 citations

Journal ArticleDOI
TL;DR: It is concluded that when nonmonotonic dose-response curves occur, the effects of low doses cannot be predicted by the effects observed at high doses, and fundamental changes in chemical testing and safety determination are needed to protect human health.
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...

2,475 citations

Journal ArticleDOI
23 Sep 2011-Thyroid
TL;DR: The revised guidelines for the management of thyroid disease in pregnancy include recommendations regarding the interpretation of thyroid function tests in pregnancy, iodine nutrition, thyroid autoantibodies and pregnancy complications, thyroid considerations in infertile women, hypothyroidism in pregnancy and thyrotoxicosis in pregnancy.
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...

2,409 citations