Cells, water quality monitoring

Bioassays appeared to fit the bill to perform this service to monitor chemical contamination. They have been around for a while. Until relatively recently, however, they remained in the realm of the laboratory. Only over the last two decades have they found a niche in testing for toxic chemicals in water and sediment, but not yet specifically as a tool for routine water quality monitoring. As Small-scale Freshwater Toxicity Investigations, Volumes 1 and 2 amply demonstrates, the science has now come of age. Assays based on bacteria, microscopic or multi-cellular algae, protozoa, invertebrates and vertebrates (freshwater fish cell cultures) are discussed in... 

The enumeration of Enterobacteriaceae and Escherichia coli in water using SPC has been the subject of several studies. These microorganisms serve as indicators of faecal contamination as part of the monitoring of the quality of raw and partially purified waters. They are also used to demonstrate the compliance of a final product with legal standards. For the selective detection of viable Enterobacteriaceae, Baudart et al. (2002,2005) used a nucleic acid probe targetting the 16S rRNA. In order to enumerate the viable cells and to increase the fluorescence intensity, FISH was combined with a DVC procedure and TSA. Using this approach, as little as one fluorescent target cell could be demonstrated in the presence of lO -lO non-fluorescent other cells. 

By the aid of a modified peptide synthesizer solutions of two moles of Boc- or Ddz-amino acid salts (sodium- or triethylammonium form) in tetrahydrofuran or dichloro-methane at —40 °C are mixed for 5 minutes with one mole of phosgene in the same solvent at —40 °C, controlled by the punched tape program of the synthesizer (Fig. 44). The solution of the symmetric anhydride is added at —40 C to the gel polymer, which is contained in the centrifugal reactor (see p. 75) and is allowed to warm up to the cooling water temperature level (9—13 C) of the reactor during the peptide synthesis period of 30 minutes. Since the mode of action of the centrifugal reactor renders it possible to perfuse an external IR flow cell with the reaction solution, we are in a position to monitor directly the quality of the symmetric anhydride and its consumption, watching the characteristic absorptions on 1,830 and 1,760 cm [71]. In several cases the symmetric anhydrides were isolated in crystalline or solid form for characterization (Table 6). 

Reflectance NIR cells allow rapid analysis of many different materials, but with some loss in precision over transmission measurement. Walling and Dabney have demonstrated the use of a conventional reflectance instrument to measure active agent content and functionality of an alcohol sulfate, as well as concentration of an additive (12). For a well-defined system, the determination of several parameters requires only a very few minutes. A reflectance NIR instrument is also suitable for quality control monitoring of surfactants and other components of powdered detergent formulations (13). NIR reflectance has even been demonstrated for detecting residues of an unspecified detergent on a stainless steel surface, with a detection limit in the 1 pg/cm range and reasonable hnearity down to about the 15 pg/cm level (14). The patent literature describes the use of NIR reflectance to determine the amount of water film left behind on a quartz tube after a surfactant solution has contacted the exterior of the tube. Within limits, the mass of the film is related to the surfactant concentration of the solution (15). 

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