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 have presented in a companion paper a suppressor-based electrodialytic buffer generator (EBG) that can produce programmable pH gradients. Here we demonstrate a three-electrode EBG. In this three-compartment flow-through device, the central compartment is separated from the outer compartments with a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM), respectively. One platinum electrode is disposed in each compartment. The flows through each compartment are independent. With appropriate solutions in each compartment, independent potentials are applied to the CEM and AEM electrodes with respect to the grounded central electrode. The CEM current and the AEM current can be independently manipulated to generate buffers with variable concentration and pH in the central compartment. Both the CEM and AEM currents can be positive or negative. For the CEM, a positive current (icatin) indicates that cations are coming in from the CEM channel to the center. A negative current (icatout) takes catio...

pH- and Concentration-Programmable Electrodialytic Buffer Generator

Although ion exchange is often depicted as a process driven by electrostatic forces, ionic solvation or hydrophobic forces contribute greatly to ion exchange selectivity and is often the dominant factor. On a variety of commercial anion exchange columns, monovalent ClO4- elutes after doubly charged SO42- and even triply charged PO43-. For identically charged alkali metal ions, electrostatic charge densities based on crystal radii would suggest Li+ to be the most strongly retained on a cation exchanger. In practice, it is typically the least strongly held cation on most cation exchangers, because of its very high hydration energy and with most eluents its capacity factor approaches zero. Even when the ion is very poorly solvated, as with tetraalkylammonium (NR4+) cations, there has never been a report on a polymeric ion exchanger of an ideal electrostatic selectivity order where NR4+ cations elute in their increasing charge density order:  R = n-butyl first, followed by n-propyl, ethyl, and last, methyl. W...

Tailoring Elution of Tetraalkylammonium Ions. Ideal Electrostatic Selectivity Elution Order on a Polymeric Ion Exchanger

Stability of sulfur dioxide in formaldehyde absorber and its anomalous behavior in tetrachloromercurate(II)

Detection by post suppression ion exchange, as an adjunct to suppressed hydroxide eluent ion chromatography, involves exchange of eluting sample anion or concurrently present H/sup +/ for a fluorescent/optically absorbing anion or cation such as anthranilate or Ce/sup 3 +/. Membrane-based post suppression devices permit reliable continuous operation, and detection limits can be better than those attainable by conductivity detection. The anion exchange membrane-anthranilate system also yields excellent detection limits by UV absorption except that membrane degradation is a problem. The ion exchange at the membrane interface is not an equilibrium process. The dependence of the membrane response on an external high frequency electrical field suggests that the transport of the ions through the membrane is not a rate-determining factor.

High sensitivity optical detection methods in hydroxide eluent suppressed anion chromatography via postsuppression ion exchange

Apparatus and method for treating a liquid sample stream including at least one analyte ion species and matrix ion species of opposite charge to said one analyte ion species. The liquid sample stream flows through a treatment channel. A carrier liquid stream including a matrix ion species capture material flows substantially parallel to the sample stream in the treatment channel forms a liquid interface between them. The matrix ion species diffuses through the interface to contact and become bound by the capture material in said carrier liquid.

Purnendu K. Dasgupta

Papers

pH- and Concentration-Programmable Electrodialytic Buffer Generator

Tailoring Elution of Tetraalkylammonium Ions. Ideal Electrostatic Selectivity Elution Order on a Polymeric Ion Exchanger

Stability of sulfur dioxide in formaldehyde absorber and its anomalous behavior in tetrachloromercurate(II)

High sensitivity optical detection methods in hydroxide eluent suppressed anion chromatography via postsuppression ion exchange

A continuous ion species removal device and method