Water sampling procedures, organic

To test the applicability of this theoretical framework in sediment, and to verify predicted exposures, bioassay(/5) and pore water sampling procedures (16J7) were developed and analytical methods were adapted to quantify the freely-dissolved concentrations (13J8). In laboratory exposures, sediment organic carbon in combination with compound were found to be good predictors of freely-dissolved chemical and organism response (19,20). 

Headspace analysis has also been used to determine trichloroethylene in water samples. High accuracy and excellent precision were reported when GC/ECD was used to analyze headspace gases over water (Dietz and Singley 1979). Direct injection of water into a portable GC suitable for field use employed an ultraviolet detector (Motwani et al. 1986). While detection was comparable to the more common methods (low ppb), recovery was very low. Solid waste leachates from sanitary landfills have been analyzed for trichloroethylene and other volatile organic compounds (Schultz and Kjeldsen 1986). Detection limits for the procedure, which involves extraction with pentane followed by GC/MS analysis, are in the low-ppb and low-ppm ranges for concentrated and unconcentrated samples, respectively. Accuracy and precision data were not reported. 

Because of their polymeric forms, alkylenebis(dithiocarbamates) are insoluble in water and most organic solvents. Additionally, they form strong complexes with different metal ions No extraction and chromatographic procedure has been reported for the parent compound of this chemical class. These compounds decompose readily under acidic conditions, for example by contact with the fruit or plant juice generated during sample preparation. 

Residue analytical methods for neonicotinoids in crops, soil and water samples have been developed. The basic principle of these methods consists of the following steps extraction of the crop and/or soil samples with acetone or the other organic solvent, cleanup by liquid-liquid partition or column chromatography, and quantitative analysis by high-performance liquid chromatography with ultraviolet detection (HPLC/UV). Simple column cleanup procedures are used to improve the accuracy and sensitivity of these methods. 

Duplicate samples were processed onshore after a variety of storage procedures. All samples were analysed for copper and iron by GFA-AS. Only samples filtered (< 1 pm), acidified, and stored frozen gave extractable copper and iron results comparable with those for samples extracted immediately after collection. Cold storage with sample acidification in polyethylene containers appeared less satisfactory. Organic extracts from samples processed onboard are best retained in all-Teflon containers pending complete digestion and analysis onshore. Unless clean (ultra-filtered air) conditions can be ensured onboard, the estuarine water samples are best returned in a filtered, acidified, and frozen condition for onshore processing. 

Krambeck et al. [40] measured small quantities of particulate carbon in lake waters by an automated furnace combustion infrared procedure. The whole sequence of operations was controlled with the aid of an AIM65 desktop computer. The system was successfully operated for routine analysis of samples of lake water with particulate organic carbon values of 100-300ug L 1 carbon a single analysis takes 8min. The relative standard deviation was about 1%. 

SIMPLICITY. No complicated equipment is needed for the implementation of solid adsorbents to accumulate organic compounds from water. The procedure is identical to gravity flow adsorption chromatography used for decades by many chemists to remove extraneous material from liquid samples in a process called sample cleanup. The simplicity of this procedure with the reduced sample manipulations minimizes solute losses and sample contamination. 

Isolation of Residue Organics from Waters via XAD Chromatography. Residue organics were isolated from the water samples via XAD chromatographic procedures developed in our laboratory. Drinking water and ground water samples were processed via the XAD procedure described in publications (3, 9, JO, 21, 22) and detailed in the Interim Protocol developed for the USEPA (5). Waste water samples were processed via a modification of the XAD procedure (4). 

The isolation method of solvent extraction has been suggested as a potentially feasible process to concentrate trace organic compounds from finished drinking water (4). One positive attribute of the solvent extraction method is that its performance for any given compound is theoretically predictable from a partition coefficient of a compound between the water sample and an organic solvent. The partition coefficient can be experimentally determined for any solute in any two-phase solvent system (7, 8). Variables of the extraction procedure such as solvent-to-water ratio and the choice of solvents can be adjusted to achieve optimum recovery. 

Thus, the collection of a representative sample becomes essential. For this reason, sample collection in this study was done for 2-4 days, and organics were extracted from 150-200 L of water. Although this method dilutes peak concentrations, the real concern with respect to micropollutants is the chronic effect (as opposed to an acute effect). Mutagenicity may result from several of the dissolved organics thus, the composite sampling procedure allows for the collection of a representative background matrix more closely associated with chronic-type exposure. 

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