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

Anion analysis continues to be of great importance to many scientific and technical fields. We propose here a general and sensitive method of detecting singly charged anions by ESI-MS and LC−ESI-MS as positive ions. This method utilizes a dicationic reagent to form a complex with the anion that retains an overall positive charge for analysis by MS. Nitrate, thiocyanate, perchlorate, perfluorooctanoic acid (PFOA), halogenated acetic acids, and various other inorganic and organic anions and are investigated. The use of tandem mass spectrometry to enhance the detection limits of some of the anions is demonstrated. Chaotropic anions provided the lowest detection limits, with PFOA detected at the hundreds of femtograms level. Indeed, this single approach provides the lowest reported detection limits for a variety of anions, especially PFOA, nitrate, monochloroacetic acid, dichloroacetic acid, and bromochloroacetic acid, among others. The integrated areas and signal-to-noise ratios for five ions during a chroma...

A general, positive ion mode ESI-MS approach for the analysis of singly charged inorganic and organic anions using a dicationic reagent.

We describe a new automated instrument for measuring gas- and aqueous-phase H2O2. The chemistry relies on the hematin-catalyzed oxidation of nonfluorescent thiamine to fluorescent thiochrome by H2O2; this reaction is 25-fold more selective for hydrogen peroxide than its nearest alkyl hydroperoxide congener, CH3HO2. The optical characteristics of the fluorescent product are such that it is ideally excited by newly available GaN-based light emitting diodes emitting in the near-UV. A stable long-life miniature flow-through fluorescence detector based on a transversely illuminated liquid core waveguide is thus used for this purpose. The limit of detection (LOD, S/N = 3) for liquid-phase H2O2 is 11 nM. A temperature-controlled high-efficiency Nafion membrane diffusion scrubber is used to collect gaseous hydrogen peroxide with near-quantitative efficiency with an S/N = 3 LOD of 13.5 pptv. The system responds to hydrogen peroxide and hydroxymethyl hydroperoxide but not to methyl hydroperoxide. The use of very in...

Measurement of Atmospheric Hydrogen Peroxide and Hydroxymethyl Hydroperoxide with a Diffusion Scrubber and Light Emitting Diode−Liquid Core Waveguide-Based Fluorometry

1,3-Cyclohexanedione was used for automated near real-time fluorometric determination of atmospheric formaldehyde. Although previous literature reports indicate this reagent to be nonselective, adaptation of a fast flow injection technique that does not rely on the completion of the reaction provided a method with a selectivity factor of >300 for HCHO over its nearest congener, CH 3 CHO. The system was optimized with respect to the reagent and scrubber liquid composition, reaction temperature, and pH. The limit of detection (LOD) in the aqueous phase is ∼6 nM (180 ng/L) HCHO for a 45-μL sample (270 fmol) with the linear dynamic range spanning >3 orders of magnitude, up to at least 14 μM

Continuous automated determination of atmospheric formaldehyde at the parts per trillion level

A droplet of a reagent solution is formed at the tip of a tube centered in a cylindrical chamber through which a gas sample is aspirated. The solution is continuously pumped ; the drop grows, falls, and another drop grows again. The droplet serves not only as a reproducible collector for the sample gas flowing around it but also as a reactor for a chromogenic reaction and as a windowless optical cell. The design and characteristics of this dynamically growing/falling droplet-based gas sensor system are described ; the performance parameters are attractive relative to a static drop. In particular, such systems can be internally calibrated for any humidity effects : at a constant pumping rate, the drop period/frequency is a predictable function of sample relative humidity. The feasibility of the sensor is demonstrated by the fully automated and continuous determination of gaseous chlorine using tetramethylbenzidine solution as a chromogenic collection liquid. At levels relevant to industrial hygiene monitoring, an 18 μL droplet-based sensor equipped with a light-emitting diode photodiode-based detector shows a relative standard deviation of 1.2% (pCl 2 ∼900 ppbv, drop period 1.1 min) while the corresponding blank standard deviation is equivalent to ∼1 ppbv. There appears to be a great potential for such drop-based collectors with in situ photometric or electrochemical signal transducers as automated sensor devices in biphasic measurements (trace gases, solvent extraction, etc.).

A Renewable Liquid Droplet as a Sampler and a Windowless Optical Cell. Automated Sensor for Gaseous Chlorine

L'ammoniac est recupere apres filtration sur membrane dans l'eau puis on le fait reagir avec l'o-phtalaldehyde et on mesure l'emission de fluorescence

Purnendu K. Dasgupta

Papers

A general, positive ion mode ESI-MS approach for the analysis of singly charged inorganic and organic anions using a dicationic reagent.

Measurement of Atmospheric Hydrogen Peroxide and Hydroxymethyl Hydroperoxide with a Diffusion Scrubber and Light Emitting Diode−Liquid Core Waveguide-Based Fluorometry

Continuous automated determination of atmospheric formaldehyde at the parts per trillion level

A Renewable Liquid Droplet as a Sampler and a Windowless Optical Cell. Automated Sensor for Gaseous Chlorine

Measurement of atmospheric ammonia