Surface waters sampling techniques

Wu et al. [388] carried out measurements of the enrichment of Atrazine on the micro surface water of an estuary. These authors used a micro surface water sampling technique with a 16 mesh stainless steel screen collecting bulk sampled from the top 100-150 pm of the surface. Atrazine concentration in the actual micro surface was estimated to vary in the range 150-8850 pg/1. 

Two questions, where to monitor or sample and how to obtain representative samples are both important. Surface water samples often are collected by automatic sampling devices controlled by a variety of sensors. The simplest method of collecting water is the grab technique, whereby a container is lowered into the water, rinsed, filled, and capped. Specialized samplers frequently are used to obtain water at greater depths. 

Nitrite photochemistry in surface waters has often been underestimated because ion chromatography, the standard technique adopted for anion (and therefore nitrate) quantification in such matrices is poorly sensitive for nitrite, which would often be below detection limit although its photochemistry could still be very significant. Accordingly, the assessment of nitrite photochemistry in surface water samples requires more sensitive, dedicated analytical techniques [104, 106, 107]. 

Moody, C.A., Kwan, W.C., Martin, J.W., Muir, D.C.G. and Mabury, S.A. (2001) Determination of perfluorinated surfactants in surface water samples by two independent analytical techniques liquid chromatography/tandem mass spectrometry and 19F NMR. Anal. Chem., 73, 2200. 

In most cases, the extracts obtained after LLE or SPE were analyzed without including a cleanup step. Laborious cleanup steps are necessary when analysis is performed by GC-EID or GC-ECD, but nowadays the most common determination technique is GC-MSD and, due to its selectivity, there is no need for a cleanup step for surface water samples. So, the cleanup step is not part of the routine methods for phthalate water analysis. It is only necessary if high background levels or high amounts of polar substances are found in the samples, as could be the case in extracts from landfill leachates of wastewaters.Cleanup is generally performed using a polar sorbent, such as activated alumina or florisil. Lopez-Avila et al. ° have compared florisil and alumina columns to perform the cleanup step. Alumina was preferred over florisil mainly because it allows recovery of all target compounds in the elution step, while three of the 16 phthalates included in the study could not be recovered with florisil clean up. 

Alkali metals, alkaline earth metals, aluminium, titanium, vanadium, chromium(iii), manganese(ii), and zinc do not interfere in the determination of hydride forming elements. These metals are frequently present in geological and biological samples, and in sea water and surface water samples. Thus, no major interferences are to be expected when these samples are analysed by the hydride generation technique. 

ESI, triazines) [537]. Recoveries observed were > 80% except for carbendazim, bu-tocarboxim, aldicarb and molinate, all better than 67% [500]. An aoTOF-MS interfaced by ESI was used to screen and identify unknown compounds and pesticides in water samples by MS and MS/MS. Structures for compounds observed besides pesticides were proposed [538]. Traces of the phenylurea pesticides Hnuron and monolinuron in water were determined quantitatively. Calibration graphs obtained after Supelclean ENVI-18 SEE were Hnear with detection limits < 25 pg [511]. Large numbers of phenylurea herbicide analyses led to the elaboration of on-line preconcentration techniques coupled to ESI-LC-MS. The procedure was demonstrated and validated with several pesticides using 10 ml of sample, resulting in detection Hmits of about 10 ng [539]. ESI-LC-MS and MS/MS were applied to quantify and to confirm 16 different herbicides of sulfonylurea [527] type in surface water samples. Surface water samples were extracted by SPE (Spe-ed RP-102). As confirmation criteria RT, molecular ion and two fragment ions besides ion abundance ratios were defined. Quantitation at 0.1 and 1.0 ppb level was demonstrated [540]. 

The methods that can be used for the determination of uranium isotopes in environmental samples were briefly surveyed (Borylo 2013). The methods were divided into radiometric methods that include different techniques of neutron activation analysis, liquid scintillation and alpha spectrometry and nonradiometric methods that include ICPMS and its variations and TIMS, and methods for assaying the amount of uranium (without isotopic composition) like ICP-OES, atomic absorption, and x-ray-based methods. The types of environmental samples listed were plants, mosses, water, soil, phosphates, sediments, and surface water. Sample preparation procedures were mentioned only in passing, stating that digestion (or mineralization) with concentrated acids (HNO3, HCl, and HE) should be followed by anion exchange on suitable resins. For alpha spectrometry, uranium was purified and deposited on steel disks (Borylo 2013). 

The collection of surface water samples generally falls into two classes of methods active or passive. Active sampling techniques involve physically taking a sample... 

From Figure 12.7, the presence of humic acids can undoubtedly be identified in the surface water sample inspected. This approach may be associated with liquid chromatography techniques, which allow for sample fractionation, identification and quantification of specific fluorophores that correlate with defined regions of the fluorescence map [19]. 

This section discusses treatment of the water samples in preparation for instrumental analysis after they have been received, archived and stored in the laboratory. Many approaches may be taken in preparation of water samples for final analysis. The techniques employed will depend upon the type of matrix, e.g., groundwater vs surface water (containing organic materials), the instrumental method and the required detection limits. 

In the adsorption with Tenax alone satisfactory results were obtained, while in the presence of mineral oil a considerable proportion of the organophos-phorus pesticides (particularly Malathion and Parathion-methyl) was not adsorbed and was recovered in the filtered water. This drawback can be overcome by adding a layer of Celite 545 which, in order to prevent blocking of the column, is mixed with silanised glass wool plugs. A number of analyses of surface and estuarine sea waters were carried out by this modified Tenax column and simultaneously by the liquid-liquid extraction technique. To some of the samples taken, standard mixtures of pesticides were also added, each at the level of 1 xg/l (i.e., in concentration from 13 to 500 times higher than that usually found in the waters analysed). One recovery trial also specifically concerned polychlorobiphenyls. The results obtained in these tests show that the two extraction methods, when applied to surface waters that were not filtered before extraction, yielded very similar results for many insecticides, with the exception of compounds of the DDT series, for which discordant results were frequently obtained. 

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