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.

Gradient anion chromatography with hydroxide and carbonate eluents using simultaneous conductivity and pH detection

Abstract: High exchange capacity membrane suppressors make gradient anion chromatography practical, with submicromolar detection limits attainable for a number of common anions when a data acquisition system is used to store a blank run and perform background subtraction. With hydroxide eluents, pH measurement yields attractive detection limits. Postsuppressors, based on a porous polypropylene tubular membrane as is, or coated with silicone rubber, permit acceptable performance with the more commonly used carbonate-based eluents. For isocratic elution with hydroxide eluents, direct potentiometric pH detection allows limits of detection only slightly worse than conductometry and is adequate for most purposes.

Capillary scale admittance detection.

Abstract: Techniques that have been variously termed oscillometric detection or (capacitively coupled) contactless conductivity detection (C4D) are known actually to respond to the admittance. It is not often appreciated that the frequency range (f) over which such systems respond (quasi)linearly with the cell conductance decreases acutely with increasing cell resistance. Guidance on optimum operating conditions for high cell resistance, such as for very small capillaries/channels and/or solutions of low specific conductance (σ), is scant. It is specially necessary in this case to take the capacitance of the solution into account. At high frequencies and low σ values, much of the current passes through the solution behaving as a capacitor and the capacitance is not very dependent on the exact solution specific conductance, resulting in poor, zero, or even negative response. We investigated, both theoretically and experimentally, capillaries with inner radii of 5–160 μm and σ ≈ 1–1400 μS/cm, resulting in cell resist...

Determination of total mercury in water and urine by a gold film sensor following Fenton's reagent digestion.

Abstract: Fenton's reagent (Fe(II) + H2O2) is utilized for the digestion of environmental water samples and urine. Following the digestion, which converts organic forms of Hg to inorganic Hg(II), Hg(0) is liberated by borohydride reduction and measured by a conductometric gold film sensor. Quantitative recovery of Hg from samples spiked with mercuric chloride, methylmercury(II) chloride, and phenylmercury(II) acetate was attainable in the presence of naturally occurring suspended matter and humic and fulvic acids as well as 3% NaCl. The digestion is performed at moderate pH (3-4) and temperature (less than or equal to 50 degrees C) and does not use large amounts of any reagent. Excellent agreement is shown for reference water, wastewater, and urine standards. The limit of detection, facilitated by the low blank value, is 500 pg of Hg or 10 ng/L for a 50-mL sample.

Hybrid fluorometric flow analyzer for ammonia.

Abstract: We describe a robust, highly sensitive instrument for the determination of ambient ammonia. The instrument uses two syringe pumps to handle three liquids. The flow configuration is a hybrid between traditional flow injection (FI) and sequential injection (SI) schemes. This hybrid flow analyzer spends ∼87% of its time in the continuous flow FI mode, providing the traditional FI advantages of high baseline stability and sensitivity. The SI fluid handling operation in the remaining time makes for flexibility and robustness. Atmospheric ammonia is collected in deionized water by a porous membrane diffusion scrubber at 0.2 L/min with quantitative collection efficiency, derivatized on-line to 1-sulfonatoisoindole, and measured by fluorometry. In the typical range for ambient ammonia (0−20 ppbv), response is linear (r2 = 0.9990) with a S/N = 3 limit of detection of 135 pptv (15 nM for 500 μL of injected NH4+(aq)) with an inexpensive light emitting diode photodiode-based detector. Automated operation in continuou...

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...