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

Reports on the microfabrication of liquid core waveguides (LCW) using Teflon/sup /spl reg// AF for integration in microfabricated micro total analysis systems. Teflon/sup /spl reg// AF has an index of refraction less than that of water. Straight micro channels (/spl les/500 /spl mu/m width, /spl les/100 /spl mu/m depth) etched into a Pyrex wafer were coated with Teflon AF and sealed with a Teflon AF coated Pyrex capping wafer. This formed a low index of refraction channel in which a higher index, aqueous solution was flowed. Light generated in the lumen propagated by total internal reflection (TIR) to the end of the channel where the light was detected using either a photomultiplier or a miniature spectrometer. An optical microscope was used to transversely illuminate the channel at various distances from the end to measure the waveguide properties.

Microfabricated liquid core waveguides for microanalysis systems

Whole column detection (WCD) is as old as chromatography itself WCD requires an ability to interrogate column contents from the outside Other than the obvious case of optical detection through a transparent column, admittance (often termed contactless conductance) measurements can also sense changes in the column contents (especially ionic content) from the outside without galvanic contact with the solution We propose here electromechanically scanned admittance imaging and apply this to open tubular (OT) chromatography The detector scans across the column; the length resolution depends on the scanning velocity and the data acquisition frequency, ultimately limited by the physical step resolution (40 μm in the present setup) Precision equal to this step resolution was observed for locating an interface between two immiscible liquids inside a 21 μm capillary Mechanically, the maximum scanning speed was 100 mm/s, but at 1 kHz sampling rate and a time constant of 25 ms, the highest practical scan speed 

https://pubs.acs.org/doi/pdf/10.1021/acs.analchem.7b01412

Admittance Scanning for Whole Column Detection

Publisher Summary The measurement of environmental samples is one of major application areas of flow analysis. The key in such an application is often the gas collection device that allows a high gas to liquid volume ratio and that permits facile automation for continuous analysis. New detectors have been developed that have made major performance improvements possible. Flow-based methods allow the measurement of many types of trace gases providing new information. This chapter explores the way to collect gaseous species and to measure gases and discusses the application of a few techniques for air analysis. Whereas many discrete samples are of interest in water analysis, the primary thrust in the analysis of air samples is automated continuous analysis. Techniques developed for trace gas analysis are useful for atmospheric analysis and also in many other areas, such as for the analysis of breath gases in clinical applications. The miniaturization of flow-based air analysis is increasingly happening, permitting more extensive applications in real field analyses. A typical flow injection analysis (FIA) system is conveniently applicable to air analysis in manual mode.

Chapter 22 - Environmental Applications: Atmospheric Trace Gas Analyses

A practical sequential injection/zone fluidicsbased analyzer that measures waterborne arsenic is capable of differentiating between inorganic As(III) and As(V). The principle is based on generating AsH3 from the sample in a confined chamber (10) by borohydride reduction at controlled pH, sparging the chamber to drive the AsH3 to a small reflective cell (70) located atop a photomultiplier tube (50), allowing it to react with ozone generated from ambient air, and measuring the intense chemiluminescence that results. Arsine generation and removal from solution results in isolation from the sample matrix, avoiding the pitfalls encountered in some solution-based analysis techniques. The differential determination of As(III) and As(V) is based on the different pH dependence of the reducibility of these species to AsH3. At pH < 1, both As(III) and As(V) are quantitatively converted to arsine in the presence of NaBH4. At a pH of 4 ~ 5, only As(III) is converted to arsine. In the present form, the limit of detection (S/N = 3) is 0.05 µg/L As at pH <= 1 and 0.09 µg/L As(III) at pH ~4 ~ 5 for a 3-mL sample. The analyzer is intrinsically automated and requires 4 min per determination. In a further embodiment, electrochemical reduction at Cd cathode is used instead of NaBH4

Purnendu K. Dasgupta

Papers

Microfabricated liquid core waveguides for microanalysis systems

Admittance Scanning for Whole Column Detection

Chapter 22 - Environmental Applications: Atmospheric Trace Gas Analyses

Method and apparatus for analyzing arsenic concentrations using gas phase ozone chemiluminescence

Determination of S(IV) at low parts per billion levels with anthranillic acid