Sampling methods waters

Schafer, R.B., A. Paschke, B. Vrana, R. Mueller, and M. Liess. 2008. Performance of the Chemcatcher passive sampler when used to monitor 10 polar and 3 semi-polar pesticides in 16 Central European streams, and comparison with two other sampling methods. Water Res. 42 2707-2717. 

G.R. Martin, J.L. Smoot, and K.D. White. A comparison of surface-grab and cross sectionally integrated stream-water-quality sampling methods. Water Environ. Res., 64 866-876,1992. 

Finally, analytical methods can be compared in terms of their need for equipment, the time required to complete an analysis, and the cost per sample. Methods relying on instrumentation are equipment-intensive and may require significant operator training. For example, the graphite furnace atomic absorption spectroscopic method for determining lead levels in water requires a significant capital investment in the instrument and an experienced operator to obtain reliable results. Other methods, such as titrimetry, require only simple equipment and reagents and can be learned quickly. 

The environmental sampling of waters and wastewaters provides a good illustration of many of the methods used to sample solutions. The chemical composition of surface waters, such as streams, rivers, lakes, estuaries, and oceans, is influenced by flow rate and depth. Rapidly flowing shallow streams and rivers, and shallow (<5 m) lakes are usually well mixed and show little stratification with... 

One standard method for determining the dissolved O2 content of natural waters and wastewaters is the Winkler method. A sample of water is collected in a fashion that prevents its exposure to the atmosphere (which might change the level of dissolved O2). The sample is then treated with a solution of MnS04, and then with a solution of NaOH and KI. Under these alkaline conditions Mn + is oxidized to Mn02 by the dissolved oxygen. 

Most organic substances can be dissolved readily in a suitable organic solvent and some are directly soluble in water or can be dissolved in aqueous solutions of acids (basic materials) or of alkalis (acidic materials). Many inorganic substances can be dissolved directly in water or in dilute acids, but materials such as minerals, refractories, and alloys must usually be treated with a variety of reagents in order to discover a suitable solvent in such cases the preliminary qualitative analysis will have revealed the best procedure to adopt. Each case must be considered on its merits no attempt at generalisation will therefore be made. It is however of value to discuss the experimental technique of the simple process of solution of a sample in water or in acids, and also the method of treatment of insoluble substances. 

A normal-phase HPLC separation seems to be useful to separate major chlorophyll derivatives, but it is not compatible with samples in water-containing solvents an additional extraction step is required to eliminate water from the extract since its presence rednces chromatographic resolution and interferes with retention times. Besides that, the analysis cannot be considered quantitative due to the difhculty in transferring componnds from the acetone solution into the ether phase. On the other hand, an advantage of the normal-phase method is its efficacy to separate magne-sinm-chlorophyll chelates from other metal-chelated chlorophyll derivatives. ... 

Isotope ratios for and Cl have been measured, and applied to chloroalkanes and chloroalkenes (Holt et al. 1997). For the Cj and C2 compounds, 8 C values ranged from -25.58 to -58.77, and 8 C1 values from -2.86 to +1.56. It was suggested that the method could be used to study the fate and distribution of such compounds. The method has, however, the disadvantage that in this method, water must first be removed from the sample. 

Similar to most Hg sampling methods, sampling sediments and soils require care in avoiding contamination artifacts due to improper sample handling. However, because Hg concentratiorrs are much higher in soUd matrices than in water, if corrrmonly accepted trace-metal protocols are used, substantial contamination artifacts should be exceedingly rare. Also, because sediment Hg concentration profiles... 

An SPE method has been developed to replace the classical LLP method. Water sample is extracted with an SPE column such as Cig and styrene-divinylbenzene copolymer (PS-2) cartridges, which consist of a reversed bonded-phase silica sorbent, provided as an extraction tool. This is a simple and rapid method, and applied to the determination of residual amounts of naproanilide, propanil, mefenacet, etc. This system determines the residual amounts of most of the pesticides and has been successfully applied to determination of pesticides in water. 

In this article, sampling methods for sediments of both paddy field and adjacent water bodies, and also for water from paddy surface and drainage sources, streams, and other bodies, are described. Proper sample processing, residue analysis, and mathematical models of dissipation patterns are also overviewed. 

No specific sample processing or preparation is needed for this method. Water samples should be warmed to room temperature prior to sampling. 

A method for determining the caffeine content of regular and decaffinated green and roasted coffee beans and of regular and decaffeinated coffee extract powders, using HPLC, is specified in a British Standard Instruction.34 Caffeine is extracted from the sample with water at 90°C in the presence of magnesium oxide. The mixture is filtered and an aliquot purified on a silica microcolumn modified with phenyl groups. The caffeine content is then determined by HPLC with UV detection.35... 

Alkaline earth oxides (AEO = MgO, CaO, and SrO) doped with 5 mol% Nd203 were synthesised by both evaporation and sol-gel methods. According to the first method, water solution of nitrates was evaporated under continuous stirring, dried, and nitrate mixture was decomposed at corresponding temperatures (Table 1) for one hour (samples designated Ev). All samples were calcined at 650°C for 3h after the decomposition. In the sol-gel method the samples (designated SG) were obtained... 

The neutron activation method for the determination of arsenic and antimony in seawater has been described by Ryabin et al. [66]. After coprecipitation of arsenic acid and antimony in a 100 ml sample of water by adding a solution of ferric iron (10 mg iron per litre) followed by aqueous ammonia to give a pH of 8.4, the precipitate is filtered off and, together with the filter paper, is wrapped in a polyethylene and aluminium foil. It is then irradiated in a silica ampoule in a neutron flux of 1.8 x 1013 neutrons cm-2 s 1 for 1 - 2 h. Two days after irradiation, the y-ray activity at 0.56 MeV is measured with use of a Nal (Tl) spectrometer coupled with a multichannel pulse-height analyser, and compared with that of standards. 

The various combustion methods differ primarily in the method of measuring the carbon dioxide generated from the organic carbon. The first really sensitive carbon dioxide detector and the one still most used is the non-dispersive infrared gas analyser. The detecting element senses the difference in absorption of infrared energy between a standard cell filled with a gas with no absorption in the infrared, and a sample cell. Water vapour is the only serious interference, hence the carbon dioxide must be dried before any measurements are made. 

Sampling Methods From the outset of the high density lake sampling program in 1987, the application of a robust and consistent sampling protocol was considered paramount and this is still the case. Lake sediment and water sampling is performed by 2-person teams primarily from float-equipped Bell 206B helicopters. 

Feenstra S, Mackay DM, Cherry JA. 1991. A method for assessing residual NAPL based on organic chemical concentrations in soil samples. Ground Water Monitoring Review 11(2) 128-136. 

A gas chromatographic procedure using electron capture detection has been described for the determination of Dursban (0,0-diethyl-0 (3, 5, 6-trichloro-2-pyridyl phosphorothioate) in water and silt [95]. In this method, water samples are extracted with dichloromethane, the extract is evaporated, and a solution of the residue is cleaned up on a column of silicic acid, Dursban being eluted with hexane. The eluate is evaporated to dryness under reduced pressure, and a solution of the residue in hexane is subjected... 

A second SFE-based method for the extraction of NPEC from solid matrices is called subcritical (hot) water extraction [9], The method was applied for NPEi 4C in 0.25 g sludge samples. Subcritical water is used as the extraction solvent, with 30% ethanol as the modifier, yielding quantitative recoveries. Other tested extraction solvent compositions were C02, hot water, methanol-modified hot water, none of which were judged satisfactory. 

Feenstra, S., Mackay, D. M., and Cherry, J. A., 1991, A Method for Assessing Residual NAPL Based on Organic Chemical Concentrations in Soil Samples Ground Water Monitoring Review, Vol. 11, No. 23, pp. 128-136. 

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