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

An organic microdrop (∼1.3 μL) is suspended inside a flowing aqueous drop from which the analyte is extracted. The drop-in-drop system is achieved by a multitube assembly. The aqueous phase is continuously delivered to the outer drop and is aspirated away from the bottom meniscus of the drop. After the sampling/extraction period, a wash solution replaces the sample/reagent in the aqueous layer, resulting in a clear outer aqueous drop housing a colored organic drop containing the extracted material. This also results in an automatic backwash. The color intensity of the organic drop, related to the analyte concentration, is monitored by a light-emitting diode based absorbance detector. After the analytical cycle, the organic drop is removed and replaced by a new one. The performance of the system is illustrated with the determination of sodium dodecyl sulfate (a methylene blue active substance) extracted as an ion pair into chloroform. This unique microextraction system is simple and flexible, permits autom...

Analytical chemistry in a drop. Solvent extraction in a microdrop.

Perchlorate, an iodide uptake inhibitor, is increasingly being detected in new places and new matrices. Perchlorate contamination has been attributed largely to the manufacture and use of ammonium perchlorate (the oxidizer in solid fuel rockets) and/or the earlier use of Chilean nitrate as fertilizer (∼0.1% perchlorate). However, there are regions such as the southern high plains (Texas Panhandle) where there is no clear historical or current evidence of the extensive presence of rocket fuel or Chilean fertilizer sources. The occurrence of easily measurable concentrations of perchlorate in such places is difficult to understand. In the southern high plains groundwater, perchlorate is better correlated with iodate, known to be of atmospheric origin, compared to any other species. We show that perchlorate is readily formed by a variety of simulated atmospheric processes. For example, it is formed from chloride aerosol by electrical discharge and by exposing aqueous chloride to high concentrations of ozone. ...

The origin of naturally occurring perchlorate: the role of atmospheric processes.

Seventy-eight metal species are examined for fluorescence properties of their chelates with 8-hydroxyquinoline-5-sutfonic acid (HQS); 42 of these fluoresce, many intensely. The optimum pH, determined by ligand ionization vs. hydroxo compiex formation, iles between 5 and 8. Cadmlum forms the most fluorescent complex In a purely aqueous solution. Fluorescence Is enhanced for many metals in surfactant (hexadecyltrlmethyiammonlum ion, HTA') containing media and in a water:dimethytformamide solvent. A number of metal ions quench the fluorescence of other metal-HQS chelates, Fe(II1) being by far the most effective, and such quenching is accentuated in media contalnlng HTA'. The fluorescence propertles can be exploited by introducing the ligand through a postcolumn reactor or by Incorporating it in the eluent in a chromatographic system. Subpicomole detection limits are attainable for Cd, Mg, and Zn.

Fluorescence Properties of Metal Complexes of 8-Hydroxyquinoline-5-sulfonic Acid and Chromatographic Applications

Recent developments in cyanide detection: A review

Perchlorate inhibits iodide uptake and may impair thyroid and neurodevelopment in infants. Recently, we unambiguously identified the presence of perchlorate in all seven brands of dairy milk randomly purchased from grocery stores in Lubbock, TX. How widespread is perchlorate in milk? Perchlorate in 47 dairy milk samples from 11 states and in 36 human milk samples from 18 states were measured. Iodide was also measured in a number of the samples. Perchlorate was detectable in 81 of 82 samples. The dairy and breast milk means were, respectively, 2.0 and 10.5 microg/L with the corresponding maximum values of 11 and 92 microg/L. Perchlorate is present in virtually all milk samples, the average concentration in breast milk is five times higher than in dairy milk. Although the number of available measurements are few at this point, for breast milk samples with a perchlorate content greater than 10 microg/L, the iodide content is linearly correlated with the inverse of the perchlorate concentration with a r2 of >0.9 (n = 6). The presence of perchlorate in the milk lowers the iodide content and may impair thyroid development in infants. On the basis of limited available data, iodide levels in breast milk may be significantly lower than it was two decades ago. Recommended iodine intake by pregnant and lactating women may need to be revised upward.

Purnendu K. Dasgupta

Papers

Analytical chemistry in a drop. Solvent extraction in a microdrop.

The origin of naturally occurring perchlorate: the role of atmospheric processes.

Fluorescence Properties of Metal Complexes of 8-Hydroxyquinoline-5-sulfonic Acid and Chromatographic Applications

Recent developments in cyanide detection: A review

Perchlorate and iodide in dairy and breast milk.