Determination sequential extraction

The procedure of simultaneous extracting-spectrophotometric determination of nitrophenols in wastewater is proposed on the example of the analysis of mixtures of mono-, di-, and trinitrophenols. The procedure consists of extraction concentrating in an acid medium, and sequential back-extractions under various pH. Such procedures give possibility for isolation o-, m-, p-nitrophenols, a-, P-, y-dinitrophenols and trinitrophenol in separate groups. Simultaneous determination is carried out by summary light-absorption of nitrophenol-ions. The error of determination concentrations on maximum contaminant level in natural waters doesn t exceed 10%. The peculiarities of application of the sequential extractions under fixed pH were studied on the example of mixture of simplest phenols (phenol, o-, m-, />-cresols). The procedure of their determination is based on the extraction to carbon tetrachloride, subsequent back-extraction and spectrophotometric measurement of interaction products with diazo-p-nitroaniline. 

Thomas, R. R, Ure, A. M., Davidson, C. M., Littlejohn, D., Rauret, G., Rubio, R., and Lopez-Sanchez, J. F., Three-Stage Sequential Extraction Procedure for the Determination of Metal in River Sediments, Analytica Chimica Acta 286, 1994, 423 29. 

Biester H., Scholz C. Determination of mercury binding forms in contaminated soils Mercury pyrolysis versus sequential extractions. Environ Sci Technol 1997 31 233-239. 

Hall G.E.M., Gauthier G., Pelchat J.C., Pelchate P., Vaive J.E. Application of a sequential extraction scheme to ten geological certified reference materials for the determination of 20 elements. J Anal At Spectrom 1996 11 787-796. 

Kim, N.D. and Fergusson, J.E., Effectiveness of a commonly used sequential extraction techniques in determining the speciation of cadmium in soils. Sci Total Environ 1991 105 191-209. 

Rapin F., Tessier A., Campbell P.G.C., Carignan R. Potential artifacts in the determination of metal partitioning in sediments by a sequential extraction procedure. Environ Sci Technol 1986 20 836-840. 

Shannon R.D., White J.R. The selectivity of a sequential extraction procedure for the determination of iron oxyhydroxides and iron sulfides in lake sediments. Biogeochem 1991 14 193-208. 

Zeien H., Brummer G.W. Determination of the mobility and binding of heavy metals in soil by sequential extraction. Mitteilungen der deutschen bodenkundlichen gesellschaft. 1991 66 397-400. 

To determine the various species and their concentrations in soil, many selective, semiselective, and sequential extraction methods have been developed. Species associated with various components in soil can be extracted with varying effectiveness (see Chapters 11 and 12). Thus, metal cations that are in solution, exchangeable, weakly held, or associated with carbonate and with... 

The aim of this work was to investigate the arsenic mobilization from the tailings material (200 - 500 pg/g As) into the seepage water (up to 3.5 mg/L As) and the process of seepage water effluent forming an immobilized precipitate (up to 8 % As) in the creek. Different analytical methods for the determination of total concentrations and different sequential extraction methods as well as hyphenated techniques for speciation analysis were applied to follow the way of the arsenic in this environment. 

Most of the applications of HPLC for protein analysis deal with the storage proteins in cereals (wheat, corn, rice, oat, barley) and beans (pea, soybeans). HPLC has proved useful for cultivar identihcation, protein separation, and characterization to detect adulterations (illegal addition of common wheat flour to durum wheat flour) [107]. Recently Losso et al. [146] have reported a rapid method for rice prolamin separation by perfusion chromatography on a RP POROS RH/2 column (UV detection at 230nm), sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE), and molecular size determination by MALDl-MS. DuPont et al. [147] used a combination of RP-HPLC and SDS-PAGE to determine the composition of wheat flour proteins previously fractionated by sequential extraction. 

The samples were analyzed for trace metals and sulfate as well as for three fractions of particulate organic matter (POM) using sequential extraction with cyclohexane (CYC), dichloromethane (DCM) and acetone (ACE). Factor analysis was used to identify the principal types of emission sources and select source tracers. Using the selected source tracers, models were developed of the form POM = a(V) + b(Pb) + - - -, where a and b are regression coefficients determined from ambient data adjusted to constant dispersion conditions. The models for CYC and ACE together, which constitute 90% of the POM, indicate that 40% (3.0 pg/m ) of the mass was associated with oil-burning, 19% (1.4 pg/m ) was from automotive and related sources and 15% (1.1 pg/m ) was associated with soil-like particles. 

A portion (10.2 cm x 17.8 cm) of each RSP sample was sequentially extracted in a Soxhlet apparatus with cyclohexane, di-chloromethane and acetone, (8 hr. for each solvent) in the order given. A more complete extraction of the organic compounds present in particulate matter is achieved and a partial separation of the organic compounds into non-polar, moderately polar and polar fractions is obtained by this method. The volume of each extract was reduced to 10.0 ml using a rotary evaporator. The samples were then stored in a freezer at -15 C until further analysis. Weights of extracts were determined by weighing duplicate 100 yl aliquots of each, taken to dryness on a slide warmer (40 C), on a Cahn Electrobalance. 

Various workers have questioned the ability of sequential extraction to provide accurate information on the mineralogical phases with which trace elements are associated in soil or sediments (e.g. Nirel and Morel, 1990). Problems, including non-selectivity of reagents and readsorption of analytes following release, are frequently reported. Hence, nowadays, most environmental analytical chemists accept that sequential extraction should be considered an operational form of speciation, in which the fractions isolated are defined purely by the sequence of reagents used, and not as a means to determine information on the specific mineralogical phases to which trace elements are bound. Modern sequential extraction procedures label the fractions obtained in terms of the type of chemical reaction used to isolate them, in order to emphasise this, e.g. reducible or oxidisable species. Unfortunately, this distinction is not always made clear in the wider environmental literature. 

Sequential extraction Reference material(s) Elements determined Reference... 

Sequential extraction is now a well-established tool in soil and sediment analysis. Although the approach is unlikely to provide precise information on the mineral phases to which trace metals are bound, it does provide useful information on potential mobilities of heavy metal contaminants which is not available from (pseudo)total metal determination. The adoption of standard protocols, such as that recommended by BCR, means that reliable and comparable data can be obtained by different laboratories. 

Ghode, R., Muley, R. and Sarin, R. (1995) Operationally determined chemical speciation of barium and chromium in drilling fluid wastes by sequential extraction. Chem. Spec. Bioavail., 7, 133—137. 

Marin, B., Valladon, M., Polve, M. and Monaco, A. (1997) Reproducibility testing of a sequential extraction scheme for the determination of trace metal speciation in a marine reference sediment by ICP-MS. Anal. Chim. Acta, 342, 91-112. 

Schultz, M.K., Burnett, W.C. and Inn, K.G.W. (1998) Evaluation of a sequential extraction method for determining actinide fractionation in soils and sediments. /. Environ. Radioactivity, 40, 155-174. 

Determine the extractable contents of the analytes using the procedure described below. Carry out all extractions on air-dried sediment. Before subsampling, ensure the sample is suitably homogenised. Take the sample using a suitable (see Apparatus) plastic spatula. For each batch of extractions, dry a separate 1 g sample of the sediment in a layer of about 1 mm depth in an oven (105 2°C) to constant mass. From this, a correction to dry mass is obtained, which should be applied to all analytical values reported (i.e. results should be quoted as amount of metal per gram of dry sediment). Perform the extractions by shaking in a mechanical, end-over-end, shaker at a speed of 30 10 rpm and a room temperature of 22 5°C. Perform the sequential extraction according to the steps described below. 

Sequential extraction experiments have been shown to provide a convenient means to determine the metals associated with the principal accumulative phases in sedimentary deposits, to elucidate the mechanisms of their diagenetic transformation, and to elucidate release processes upon changing environmental conditions (Kersten and Forstner, 1989). A general goal of all studies involving selective chemical extraction is the accurate determination of partitioning of elements of environmental concern among different discrete phases of a sample. 

Table 11.1 Sequential extraction results for cadmium and zinc for the dried but originally anoxic harbour sediment samples compared with the probability of association of both metals with major elements as determined by direct electron microprobe study of the same sediments, in percentages (95% confidence level data from Lee and Kittrick, 1984)...

Martens, DA. and Suarez, D.L. (1997) Selenium speciation of soil/sediment determined with sequential extractions and hydride generation atomic absorption spectrometry. Environ. Sci. Technol., 31, 133. 

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