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.

The origins and the future of microfluidics

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.

Intrinsic peroxidase-like activity of ferromagnetic nanoparticles

http://lovely-physics.persiangig.com/document/DLLME.pdf

Determination of organic compounds in water using dispersive liquid-liquid microextraction

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...

/pdf/hormones-and-endocrine-disrupting-chemicals-low-dose-effects-2vn32zoqc8.pdf

Hormones and endocrine-disrupting chemicals: Low-dose effects and nonmonotonic dose responses

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...

https://www.thyca.org/download/document/486/PregnancyandPostpartum.pdf

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

We introduce a new concept for continuous on-line titrations based on feedback-controlled flow ratiometry and the principle of compensating errors. The system has been thoroughly tested by applying it to acid−base neutralization titrations with indicator-based end point detection. In a typical case, the total flow (FT, consisting of the sample and the titrant flows) is held constant while the titrant (e.g., a standard base containing an indicator) flow FB varies linearly in response to a controller output voltage. The sample (e.g., an acidic solution to be titrated) flow FA constitutes the makeup and thus also varies (FA = FT − FB). The status of the indicator color in the mixed stream is monitored by an optical detector and used either for governing the controller output or for interpreting the results of the titration. Three methods (PID based control, fixed triangular wave control, and feedback-based triangular wave control implemented on a PC) were examined. In the last and the most successful approac...

Continuous on-line true titrations by feedback-based flow ratiometry. The principle of compensating errors

Live HeLa cells immobilized on Sephadex G-50 beads were used as a medium for the preconcentration and speciation of inorganic arsenic. The sorption of arsenic species by live HeLa cells involves both surface uptake and bioaccumulation within the cells. At pH 3.0, the cells accumulate arsenate with high specificity over arsenite: 83.0 ± 1.3% of the arsenate was sorbed while the retention of arsenite was negligible at 2.1 ± 0.6%. The speciation of inorganic arsenic could thus be performed by direct determination of arsenate followed by quantifying total inorganic arsenic after conversion of arsenite to arsenate. We formed a disposable live cell preconcentration microcolumn with the live HeLa cells immobilized on Sephadex G-50 beads. After the sample was passed through the column for sorption to occur, the cells and any retained arsenate were stripped with 2 M HNO3. The arsenic in the 30 μL eluate was directly measured by graphite furnace atomic absorption spectrometry. A new microcolumn was used for each sa...

https://pubs.acs.org/doi/pdf/10.1021/ac802475b

Live HeLa Cells Preconcentrate and Differentiate Inorganic Arsenic Species

An affordable high-performance optical absorbance detector for capillary systems

Expanding the linear dynamic range for multiple reaction monitoring in quantitative liquid chromatography-tandem mass spectrometry utilizing natural isotopologue transitions.

Conductivity detectors sufficiently small for deployment in capillary analytical systems can be fabricated very simply and reproducibly from commonly available micro assemblies of multiconductor ribbons. It results in a unique geometry for the conductivity detection cell where the fluid does not flow between the electrodes. Interface circuitry for a personal computer (PC)-based bipolar pulse conductance detector is described. The cell can be used with this or commercial detectors. Results obtained with the new cell and electronic design in a suppressed conductometric capillary electrophoresis separation system are presented

Purnendu K. Dasgupta

Papers

Continuous on-line true titrations by feedback-based flow ratiometry. The principle of compensating errors

Live HeLa Cells Preconcentrate and Differentiate Inorganic Arsenic Species

An affordable high-performance optical absorbance detector for capillary systems

Expanding the linear dynamic range for multiple reaction monitoring in quantitative liquid chromatography-tandem mass spectrometry utilizing natural isotopologue transitions.

Computer-Interfaced Bipolar Pulse Conductivity Detector for Capillary Systems