Waters® AMDS system

In addition to schwertmannite, some other minerals of Fe(in) are commonly recognized in the AMD systems, with a close relation between their occurrence and the water pH (Table 1). Jarosite is usually favored to precipitate from very acidic solutions, normally at pH < 2. Schwertmannite precipitates near the discharge points at pH 2.0-4.0, whereas ferrihydrite usually forms in fluvial environments (as in the confluences between AMD and unpolluted rivers) at... 

The process depicted for phenol in equations 5 consists of an enzyme-catalyzed oxidation to a quinone, and a reduction process taking place at the electrode these reactions may serve for electrode calibration. The development of AMD biosensors for detection of phenols in environmental waters has been described for phenoloxidases such as tyrosinases and laccases and less specific oxidases such as peroxidases. Such biosensors may be part of a FIA system for direct determination of phenols or may serve as detectors for LC °. 

Pervaporation in a FIA system was proposed as a preconcentration step for the determination of phenol in water. This involves placing the sample in concentrated brine at pH 2, diffusion of the salted out phenol present in the headspace through the pervaporation membrane into a collecting alkaline solution and AMD using a GCE set at +0.6 V. At 20°C, LOD was 0.9 mgL, with linearity in the 1-50 mgL range and RSD 1-4% (n = 3). The sample thoughput was 5 per hour. ... 

High performance thin-layer chromatography (HPTLC) has also been used for the determination of carbamate pesticides.Thus, TLC methods provide increased selectivity through silica derivatization, as well as higher analytical precision and sensitivity with high-performance plates. Butz and Stan reported an HPTLC system with automated multiple development (AMD-HPTLC) to screen water samples for pesticides. The method was applied to the determination of 265 pesticides in drinking water spiked with 100 ng/1 of each analyte. 

AIMD is still a very time-consuming simulation method, and has so far mainly been used to study the structure and dynamics of bulk water, as well as proton transfer and simple Sn2 reactions in bulk water. AIMD simulations are as yet limited to small system sizes and real simulation times of not more than a few picoseconds. However, some first applications of this technique to interfacial systems of interest to electrochemistry have appeared. There is no doubt that AMD simulations of electrochemical interfaces will become increasingly important in the future, and some interesting first results will be described in Sections III.7 and III.8. 

Conaway et al. (1995) extended the above-mentioned study of Perez et al. (1994) to determine by densitometric-HPTLC sugars in Helisoma trivolvis snails infected with the larval trematode Echinostoma trivolvis. Zarzycki et al. (1995) examined the retention properties of alpha-, beta-, and gamma-cyclodextrins using water-wettable RP-C-18 layers and mobile phases composed of acetonitrile, methanol, ethanol, or propanol with water or methanol in acetonitrile. Esaiassen et al. (1995) analyzed n-acetylchitooligosaccharides by use of the latroscan TLC/ flame ionization detection (FID) system. Brandolini et al. (1995) used automated multiple development (AMD)-HPTLC to monitor various carbohydrates—i.e., maltotetraose, maltotriose, maltose, glucose, and fructose—in different beers. 

Dina L. Lopez (hydrogeology water quaht) environmental geochemistry geochemistry of hydrothermal systems fluid flow and heat transfer acid mine drainage (AMD) and arsenic contamination in water environmental causes of chronic kidney disease of unknown etiology). Department of Geological Sciences, Ohio University, Athens, OH... 

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