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

Many of the universal detectors in liquid chromatography, including mass spectrometry, must completely volatilize the chromatographic eluent first before further processing and detection of the analytes. A basic requirement is that the eluent does not contain a nonvolatile dissolved component. However, separation of biomolecules must be conducted in mostly aqueous media of compatible pH and ionic strength if their biological activity must survive the separation process. Combinations of ammonia with acetic and formic acids are commonly used as eluent for this purpose but generally maximum concentrations that can be tolerated are relatively low. Further, buffering is good only over a limited pH range. We describe a system where the eluent is generated in an automated pressure-programmed manner from high-purity gaseous NH3 and CO2 through gas-permeable membrane devices. This can be aided by the prior presence of formic/acetic acids in the mobile phase to extend the attainable low pH limit. We outline the fundamental pH, ionic strength, and buffer intensity considerations and demonstrate the application of such eluents in the separation of amino acids, proteins, and monoclonal antibodies. We also demonstrate the use of dissolved CO2 as an ion-pairing agent in the separation of chiral amines.

Automated Programmable Generation of Broad pH Range Volatile Ionic Eluents for Liquid Chromatography.

We successfully fabricated 45 μm bore microchannels in PVA-Poly(styrenesulfonate) cation exchange polymers. by casting aqueous prepolymer mixtures around fine tungsten wire mandrels, curing, crosslinking by thermal annealing, and subsequently removing the microwire. This was then used as a chemically regenerated microsuppressor (with a cleaner MS background than its commercial macro counterparts) for open tubular ion chromatography, with an integrated tubular conductivity cell, tested to backpressures up to 600 psi. The overall system permits detection limits for common inorganic ions in the low μg/L levels with a 4-nL injection, isocratic elution and regeneration with poly(styrene sulfonic acid).

Moldable capillary suppressor for open tubular ion chromatography based on a polymeric ion exchanger.

Open tubular capillary columns for liquid and ion chromatography, based upon an ionically impermeable polyolefin capillary having a bore with a sulfonate-group- or amine-group-functionalized internal surface The capillary columns may include a coating of ion exchanging nanoparticles electrostatically bound to the functionalized internal surface The capillary columns may be made by exposing the interior surface to a sulfonating reagent comprising chlorosulfonic acid (ClSO 3 H), preferably from 85 wt % to 95 wt % chlorosulfonic acid at a process temperature of 20 to 25° C The interior surface may be subsequently exposed to an asymmetrical diamine to form a sulfonic mid-linkage to the diamine, ie, to form a sulfonamide-linked, amine-group-functionalized internal surface The coating may be provided by subsequently exposing the interior surface to an aqueous suspension of ion exchanging nanoparticles to electrostatically bond the ion exchanging nanoparticles to the functionalized internal surface

Functionalized polyolefin capillaries for open tubular ion chromatography

The production and characterization of a transition metal Fe(III)-sulfur(IV) aerosol

Small inexpensive soil water sensors and the necessary electronics package for fast voltammetry (l04 V/s scan rate) are described. The sensor consists of a blunt ended hypodermic needle cathode containing a concentric PTFE insulating tube and therein, a Pt-wire anode. The sensing film is formed by dip-coating a 1:7 blend of a perfluorosulfonate and a polyestersulfonate polymer at the tip of the needle. Atop this sensing film is a composite protective film of cellulose acetate and nylon that inhibits the passage of ionic or low MW constituents and allows the transport of water. The sensor is sheathed in a PTFE tube that protrudes beyond the sensor tip and the protrusion gap is filled with a paste of talc and BaSO4 which serves as a water conduit between the soil and the sensor proper. The sensor is capable of making reliable moisture measurements between the wilting point and the field capacity of the soil sample; the response behavior consists of the combination of two nearly linear segments, the sensor output increasing steeply between the wilting point and ca. 60% of the field capacity and then much more gradually to the field capacity. The sensors have been field tested. No effect on sensor performance is observed even after burial under soil for several months.

Purnendu K. Dasgupta

Papers

Automated Programmable Generation of Broad pH Range Volatile Ionic Eluents for Liquid Chromatography.

Moldable capillary suppressor for open tubular ion chromatography based on a polymeric ion exchanger.

Functionalized polyolefin capillaries for open tubular ion chromatography

The production and characterization of a transition metal Fe(III)-sulfur(IV) aerosol

Fast voltammetric sensors for the measurement of soil water activity