Spot water samples

Among the kinetic sampling devices, ceramic dosimeters have been used successfully for the long-term surveillance of VOCs.92 They use a ceramic tube as the diffusion-limiting barrier that encloses a receiving phase consisting of solid sorbent beads. Over a three-month deployment in a contaminated aquifer, the ceramic dosimeter provided TWA concentrations of benzene, toluene, ethylbenzenes, xylenes, and naphthalenes. The levels obtained matched closely those found in spot water samples that were taken frequently over the trial period.54... 

Besides the advantages that passive sampling may offer, it is important to recognize that in many cases these devices measure a different fraction of contaminants than that defined for the checking of EQS compliance within the WFD. This becomes especially important when monitoring very hydrophobic chemicals (log Kow > 4), where a large fraction of the total amount present in a spot water sample is bound to colloids and particles. In contrast, most passive samplers used for monitoring hydrophobic compounds (e.g., SPMD, Chemcatcher, and silicone materials) measure only the truly dissolved fraction of these chemicals. 

On-site determinations of N03 concentrations were made using the Pastel UV at 37 sites in the Weiherbachgraben and Sauruntz sub-basins of the Hardt catchment. Both surface and ground waters were sampled over a two-day field campaign. In addition spot water samples were collected for analysis by ion chromatography in the laboratory. Immediately after collection an aliquot of the water sample was filtered through a 0.45 pm cellulose acetate filter (Millipore) and stored in a polyethylene bottle at 4-8°C until analysis. 

The separation of uncolored samples is usually done on TLC plates containing a fluorescent dye so as to use the fluorescence-quenching effect for sample location. If such plates are not available or if samples show no quenching effect, two universal reagents can help. If the TLC plate is simply sprayed with water, sample spots are very often not translucent but white. Clearer zones can be obtained sometimes by first saturating... 

SFE-GC-MS is particularly useful for (semi)volatile analysis of thermo-labile compounds, which degrade at the higher temperatures used for HS-GC-MS. Vreuls et al. [303] have reported in-vial liquid-liquid extraction with subsequent large-volume on-column injection into GC-MS for the determination of organics in water samples. Automated in-vial LLE-GC-MS requires no sample preparation steps such as filtration or solvent evaporation. On-line SPE-GC-MS has been reported [304], Smart et al. [305] used thermal extraction-gas chromatography-ion trap mass spectrometry (TE-GC-MS) for direct analysis of TLC spots. Scraped-off material was gradually heated, and the analytes were thermally extracted. This thermal desorption method is milder than laser desorption, and allows analysis without extensive decomposition. 

Protein Analysis. Protein concentrations were determined with a Spectronic 20 spectophotometer employing BSA as a standard (12). Each 0.1 ml sample was spotted on 3 cm2 Whatman No. 42 filter paper and air dried. Samples were stained with Xylene Brilliant Cyanin G (K and K Laboratories, Cleveland, Ohio), and the absorbance at 610 nm was recorded against a blank containing distilled water. Samples were corrected using controls containing all components except protein. 

Add 200 pi water to the cell pellet and sonicate briefly at low power. Use 50 pi homogenate for a protein determination and 100 pi for lipid extraction. To 100 pi homogenate add 4 ml chloroform/methanol 2/1 (v/v). Leave for 1 h at room temperature and add 0.8 ml of 0.73% NaCl. Vortex and centrifuge for 5 min at 1000xg to separate the phases. Remove the lower chloroform phase and add 10 nmol cho-lesteryl oleate and 10 nmol triolein as a cold carrier. Dry the sample under nitrogen. Take the sample up in 25 pi chloroform/methanol 2/1 (v/v) and spot the sample on a silica gel plate (0.5 cm streak). Rinse the tube with 25 pi chloroform/methanol 2/1 (v/v) and spot the sample on a silica gel plate. Develop the plate with hexane/diethyl-ether/acetic acid, 70/30/1 (v/v/v). Remove the plate from the tank when the solvent front almost reaches the top, dry the plate, and expose briefly to iodine vapor to localize the cholesteryl oleate. Scrape the spots into scintillation vials, mix thoroughly, and count in a scintillation counter. 

Ground water samples can be collected from monitoring or supply wells. Their location is not always straightforward—generally such water is sampled over hot spots and near locations following the subterranean stream in order to detect plume profile movements.19 The depth of the well and the characteristics of the surrounding land surface and upstream activities can help in the interpretation of results. 

One approach to help overcome this disparity between spot and passive sampling data is to use additional water quality data. If average values of DOC, suspended particulate matter, and total organic carbon content are known, it may be possible to estimate the total concentration using empirical relationships that describe the distribution of a chemical between the different phases that may be present in an environmental water sample.121 There is, however, uncertainty associated with this approach, as a number of assumptions are made in the calculations and a better understanding of the partitioning behavior of priority pollutants between the different phases is needed. 

Rump [17] has described a cellulose thin layer method for the detection of phenolic acids such as iw-hydroxybenzoic acid, iw-hydroxyphenylacetic acid and m-hydroxyphenylpropionic acid, in water samples suspected to be contaminated with liquid manure. The phenolic acid is extracted with ethyl acetate from a volume of acidified sample equalling lmg of oxygen consumed (measured with potassium permanganate). The ethyl acetate is evaporated and the residue dissolved in ethanol. After spotting of a lpm aliquot on a cellulose plate the chromatogram is developed by capillary ascent with the solvent n-propanol-w-butanol-25% NH3-water (4 4 1 1 by vol). The solvent front is allowed to advance 10cm. The air-dried plate is sprayed with a diazotised p-nitroanilinc reagent to make the phenolic acids visible. 

There are various factors that can influence the distribution of analytes in a dried blood spot. Water-soluble chemicals uniformly coated on DBS cards would redistribute when the blood was spotted. The redistribution of chemicals may depend on their properties, viscosity of blood, the volume spotted, and the technique used for spotting. Another factor is the viscosity of the blood. Viscosity is normally dependent on the blood composition (hematocrit, protein, lipid levels), and it can affect the physical spread of the blood spot in that the same volume of a less viscous blood will form a larger diameter spot than that of a more viscous blood sample. Viscosity, combined with the chemical redistribution on the sample cards, will increase the complexity of the analyte distribution. 

The urine creatinine concentration should be used to normalize the quantity of any analyte of interest, as this will correct for incomplete urine collection or urine dilution that may have resulted from drinking water spillage within the metabolism cages (Haas et al. 1997). The quantity of creatinine in a spot urine sample serves as an accurate index of the 24 hour urine output in most species. 

In paper chromatography the stationary phase is the cellulose of the paper, and the spot of sample is added to the paper. A suitable solvent, say water or alcohol, is called the mobile or moving phase. This is added to push the materials across the paper or a thin layer of powder as it soaks across. Each material in the mixture to be separated will have a different solubility in the solvent and also a different degree of adsorption (sticking) to the paper. As the solvent soaks along the paper, the sample repeatedly becomes dissolved in the solvent and adsorbed and desorbed to and from the paper. These variables make the time it takes for a material to move along unique for each material in the mixture. 

Jha AR, et al. 1979. A sensitive and selective spot test method for the detection of vanadium(V) in a water sample. Int J Environ Stud 14 235-236. 

In April 1982, before crops were planted, the drill rig was used to collect water samples from spots directly beneath the growing area of Field 5. A 30-cm metal well point with stainless-steel screen welded to the end of a section of hollow-stem auger was drilled to various depths below treated areas. Water samples were withdrawn through Teflon tubing inserted down the hollow stem into the point using the peristaltic pump. Sediment-free samples were bottled and stored for analysis as previously described. 

The type of water sample to be taken at each site is part of the strategy for the monitoring programme. For most water bodies, spot samples are likely to be appropriate. In specific situations, where pollutant concentrations are heavily influenced by flow conditions and temporal variation, and if pollution load assessments are to be performed. Other more representative types of sample may be beneflcial. Flow-proportional or time-proportional samples may be better in such cases. A single depth sample might not be adequate to reflect the situation in stratifled water bodies such as lakes, estuaries and coastal areas. Hence, waters samples should be taken at several depths at such locations. For example, multiparameter probes (e.g. CTD probes) can be employed to detect stratifications. 

Use the entire contents of the transport flask for the extraction. In the case of volumes larger than 1 litre, evaporate to 1 litre. Transfer the water sample prepared in this way, including the solution of the sediment, to a 1.3-litre shaking funnel, set the pH to about 3 by adding hydrochloric acid or ammonium hydroxide solution dropwise (test by spotting onto indicator paper), treat with 2 ml of DDTC solution, shake for 10 seconds, then... 

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