Sediment aqueous extract

Analysis of soils and sediments is typically performed with aqueous extraction followed by headspace analysis or the purge-and-trap methods described above. Comparison of these two methods has found them equally suited for on-site analysis of soils (Hewitt et al. 1992). The major limitation of headspace analysis has been incomplete desorption of trichloroethylene from the soil matrix, although this was shown to be alleviated by methanol extraction (Pavlostathis and Mathavan 1992). 

Chemical Analyses of Aqueous Extracts. Subsequent to the demonstration of hydrilla growth inhibition by the crude sediment extract, basic information concerning select characteristics was obtained. 

Obtaining consistent chromatograms of aqueous extracts provides a means of characterizing the presence of a hydrilla-growth inhibitor in natural waters (19). Some examples are provided in Table II, where the location of the second fraction is indicated as percentage of the programmed run. Three different sediment samples were compared for Lake Starvation with consistent results. The fraction obtained for the extract of Lake White Trout is similar to the fraction for Lake Starvation. Hydrilla disappeared from Lake Kerr (located in Marion County, Florida, and the sediment obtained at the time yielded an aqueous extract that appears to contain the hydrilla inhibitor. 

Drugs have been purified by SPE in the analysis of amphetamine (AM) by Kaleta et al. [98], by various consecutive washing steps with hexane in the analysis of methamphetamine (MA) by Jones-Lepp and Stevens [99], and by simple centrifugation after addition of water, to separate the aqueous extract from a bottom sediment layer and a top fat layer, in the analysis of AM, MA, cocaine (CO), and benzoylecgonine (BE) by Langford et al. [100], who found little improvement in reducing matrix effects when applying SPE cleanup. 

Kido et al. [6] determined basic organic compounds such as quinoline, acridine, aza-fluorene, and their N-oxides in marine sediments found in an industrial area. The sediments were extracted with benzene by using a continuous extractor for 12h. Hydrochloric acid solution (IN) was added to the benzene extracts, and the mixture was shaken for 5min the acid layer separated from the benzene layer was made alkaline by the addition of sodium hydroxide, and the alkaline aqueous solution was extracted with diethyl ether the ether extracts were then dehydrated with anhydrous sodium sulphate and concentrated with a Kuderna-Danish evaporator. The concentrations were separated and analysed by gas chromatography-mass spectrometry and gas chromatography high-resolution mass spectrometry. 

The method for analysing sediment involves extraction of organochlorine insecticides and polychlorobiphenyls with a mixture of acetone and hexane together with 1% aqueous ammonium chloride. The extracts are then concentrated for purification with concentrated sulphuric acid and aqueous sodium sulphite in the presence of tetrabutylammonium sulphate and finally gas chromatographic analysis is applied. 

Normal-phase HPLC has also found application in the analysis of pigments in marine sediments and water-column particulate matter. Sediments were extracted twice with methanol and twice with dichloromethane. The combined extracts were washed with water, concentrated under vacuum and redissolved in acetone. Nomal-phase separation was performed with gradient elution solvents A and B being hexane-N,N-disopropylethylamine (99.5 0.5, v/v) and hexane-2-propanol (60 40, v/v), respectively. Gradient conditions were 100 per cent A, in 0 min 50 per cent A, in 10 min 0 per cent A in 15 min isocratic, 20 min. Preparative RP-HPLC was carried out in an ODS column (100 X 4.6 mm i.d. particle size 3 jum). Solvent A was methanol-aqueous 0.5 N ammonium acetate (75 25, v/v), solvent B methanol-acetone (20 80, v/v). The gradient was as follows 0 min, 60 per cent A 40 per cent A over 2 min 0 per cent A over 28 min isocratic, 30 min. The same column and mobile phase components were applied for the analytical separation of solutes. The chemical structure and retention time of the major pigments are compiled in Table 2.96. 

Soils, sediments, or solid wastes mixed with water and subjected to purge and trap concentration aqueous extract may directly be injected onto GC sample/extract analyzed as above. 

Appraising the toxic potential of biologically available contaminants in sediment should include three compartments the whole sediment (with standardized direct contact assays when these are available), the porewater, and the elutriate (aqueous extract). Additional hazard information can also be obtained from toxicity testing conducted on organic extracts using methanol or acetone. 

For porewater extraction, whole wet sediment is centrifuged at 17,000 x g for 20 min. An elutriate (aqueous extract) is obtained by shaking the wet sediment sample in an aerobic milieu for 24 h. Soluble substances are extracted under such conditions. The elution process is performed with the original wet sediment and the... 

Conventional Raman spectroscopy cannot be applied directly to aqueous extracts of sediments and soils, although it is occasionally used to provide information on organic solvent extracts of such samples. Fourier transform Raman spectroscopy, on the other hand, can be directly applied to water samples. The technique complements infrared spectroscopy in that some functional groups, eg unsaturation, give a much stronger response in the infrared. Several manufacturers (Perkin-Elmer, Digilab, Broker) now supply Fourier transform infrared spectrometers. 

Fulvic acid organic matter of complex composition which remains soluble when an aqueous extract of sediment or soil is acidified. 

One method to determine which of these two possibilities is correct is to measure 5 S of sulfate in aqueous extracts of drift and bedrock sediments and compare with values for marine evaporite gypsum and for Alberta coal. 

Protein molecules extracted from Escherichia coli ribosomes were examined by viscosity, sedimentation, and diffusion experiments for characterization with respect to molecular weight, hydration, and ellipticity. These dataf are examined in this and the following problem. Use Fig. 9.4a to estimate the axial ratio of the molecules, assuming a solvation of 0.26 g water (g protein)"V At 20°C, [r ] = 27.7 cm g" and P2 = 1.36 for aqueous solutions of this polymer. 

A pilot plant ia India has been estabUshed to extract fiber, pulp, and juice from the leaves of sisal plants. The fiber is sold direcdy or used to manufacture rope, the cmshed pulp is used ia paper processiag, and the juice is an excellent source of hecogenin. During a three- to five-day fermentation of the juice, partial enzymatic hydrolysis causes hecogenin to precipitate as the hemisaponin ia the form of a fine sludge. This sediment is hydrolyzed with aqueous hydrochloric acid, neutralized, and filtered. This filter cake is washed with water and extracted with alcohol. The yield of hecogenin varies between 0.05 and 0.1% by the weight of the leaf (126). 

Results. Various solvent mixtures were tested for extraction efficiency. The test sample was a bone-dry sediment reference material containing 24.6 ppm of Arochlor 1242. This reference material is a real sediment from New Bedford Harbor which was homogenized and carefully assayed for PCB s by the Cincinnati EPA facility. Figure 3 shows recovery of 1242 using (1) hexane alone, (2) hexane and water (1 1), (3) hexane, water, and ethyl ether, (4) ethyl ether and water, (5) ethyl ether, water, and methanol, (6) methanol and hexane (1 1), and (7) water, methanol, and hexane (1 4 5). This last combination appears to give the best recovery. When added in this order to a dry sample, the effect of the water is to wet the sample, thus permitting extraction by methanol. The extracted PCB is partitioned almost exclusively into the hexane from the aqueous methanol. Final recovery is calculated from initial weight and hexane volume. 

For pesticide residue immunoassays, matrices may include surface or groundwater, soil, sediment and plant or animal tissue or fluids. Aqueous samples may not require preparation prior to analysis, other than concentration. For other matrices, extractions or other cleanup steps are needed and these steps require the integration of the extracting solvent with the immunoassay. When solvent extraction is required, solvent effects on the assay are determined during assay optimization. Another option is to extract in the desired solvent, then conduct a solvent exchange into a more miscible solvent. Immunoassays perform best with water-miscible solvents when solvent concentrations are below 20%. Our experience has been that nearly every matrix requires a complete validation. Various soil types and even urine samples from different animals within a species may cause enough variation that validation in only a few samples is not sufficient. 

Koide et al. [537] have described a graphite furnace atomic absorption method for the determination of rhenium at picomolar levels in seawater and parts-per-billion levels in marine sediments, based upon the isolation of heptavalent rhenium species upon anion exchange resins. All steps are followed with 186-rhenium as a yield tracer. A crucial part of the procedure is the separation of rhenium from molybdenum, which significantly interferes with the graphite furnace detection when the Mo Re ratio is 2 or greater. The separation is accomplished through an extraction of tetraphenylarsonium perrhenate into chloroform, in which the molybdenum remains in the aqueous phase. 

Spengler and Jumar [90] used a spectrophotometric method and thin layer chromatography to determine carbamate and urea herbicide residues in sediments. The sample is extracted with acetone, the extract is evaporated in vacuo at 40°C and the residue is hydrolysed with sulphuric acid. The solution is made alkaline with 15% aqueous sodium hydroxide and the liberated aniline (or substituted aniline) is steam distilled and collected in hydrochloric acid. The amine is diazotized and coupled with thymol, the solution is cleaned up on a column of MN 2100 cellulose power and the azo-dye is determined spectrophotometrically at 440nm (465nm for the dye derived from 3-chloro- or 3.4-dichloroaniline) with correction for the extinction of a reagent blank. 

In a similar procedure [32] the sediment is wet oxidised with dilute sulphuric acid and nitric acids in an apparatus in which the vapour from the digestion is condensed into a reservoir from which it can be collected or returned to the digestion flask as required. The combined oxidised residue and condensate are diluted until the acid concentration is IN and nitrate is removed by addition of hydroxylammonium chloride with boiling. Fat is removed from the cooled solution with carbon tetrachlodithizone in carbon tetrachloride. The extract is shaken with 0.1M hydrochloric acid and sodium nitrite solution and, after treatment of the separated aqueous layer with hydroxylammonium chloride a solution of urea and then EDTA solution are added to prevent subsequent extraction of copper. The liquid is then extracted with a 0.01% solution of dithizone in carbon tetrachloride and mercury estimated in the extract spectrophotometrically at 485nm. 

Bartlett et al. [55] used the method of Uthe et al. [70] for determining methylmercury. Sediment samples of 2-5g were extracted with toluene after treatment with copper sulphate and an acidic solution of potassium bromide. Methylmercury was then back extracted into aqueous sodium thiosulphate. This was then treated with acidic potassium bromide and copper sulphate following which the methylmercury was extracted into pesticide grade... 

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