Sequential extraction process

Chang, D., Hojilla-Evangelista, M.P., Johnson, L.A., and Myers, D.J. 1995. Economic-engineering assessment of sequential extraction processing of com. Trans. ASAE 38, 1129-1138. 

Details about sequential extraction process parameters [25]... 

Hojilla-Evangelista MP. Sequential Extraction Processing Alternative Technology for Corn Wet-milling [Ph.D. Thesis], Ames, IA Iowa State University 1990. 

When extracting chondroitin sulfate from salmon head cartilage, collagen inevitably accompanies it. In this extraction process, from a pharmaceutical point of view, collagen is considered as an impurity. This is a kind of contradiction because if we administrate chondroitin sulfate and collagen simultaneously, the result will be beneficial and effective. Most marine bioresources contain many health beneficial compounds even in the same tissues. For this reason, we should design sequential extraction processes of those useful compounds from the most value added to the poorly valued compounds. For example, the first step for pharmaceutical use should be the mild extraction of compounds. And the final step should extract materials for fertilizers. 

It can be seen that the two soils behaved differently to the sequential extraction process. On average (for both soils) ca. 50% of the metal content was in the residual fraction, i.e. unlikely to be released. The majority of iron was always in the residual fraction (54% for Soil A and 92% for the CONTEST soil). 

In the present work it has been shown that on-line coupling of flowthrough fractionation in RCC with ICP-EAS detection enables not only the fast and efficient fractionation of trace elements (TE) in environmental solids to be achieved but allows real-time studies on the leaching process be made. A novel five-step sequential extraction scheme was tested in on-line mode. The optimal conditions for the fractionation were chosen. Investigating elution curves provides important information on the efficiency of the reagents used, the leaching time needed for the separation of each fraction, and the potential mobility of HM forms. 

There have been some questions raised about the validity of results of extensive and sequential extraction methods. There is the possibility that species of an analyte may change during the extraction process. It is also possible that a species may be liberated and then reabsorbed during extraction or subsequent isolation. The same or similar question could be raised about various initial sampling and subsequent storage methodologies as described next. In spite of these questions, the BCR methodology has been widely accepted [39-41],... 

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. 

Keywords Biosorption Activated sludge process Removal of heavy metals Sequential extraction of metals Metal uptake... 

A major limitation to the widespread adoption of sequential extraction for trace element speciation is the lengthy sample processing time (e.g. three 16-h periods of mechanical shaking for the BCR method). Various authors have attempted to develop more rapid means of extraction, involving ultrasonic or microwave assistance. The goal of such studies is generally to obtain performance similar to... 

Analysis of variance (ANOVA and MANOVA) has been used to investigate the influence of location on forms of metals in roadside soil (Nowak, 1995). Multiple regression analysis has proved valuable in processing sequential extraction data to obtain information on plant availability of trace metals in soils (Qian et al, 1996 ... 

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. 

Speciation of metal content in solids can be accomplished during the extraction process by subjecting the sample to successive extractions with progressively more aggressive solvents, or by extracting different subportions of sample with the different solvents. It has been shown that it is more difficult to obtain comparable results when using sequential extractions rather than individual extractions of subsamples with different extractants [124]. Some applications of extractions with different solvents are extraction with ... 

Accelerated solvent extraction (ASE) is becoming more popular because of its rapidity. This however is offset by sequential sample processing. Samples are placed in a stainless steel vessel and subj ected to solvent at elevated pressure and temperature. The pH of the extraction can be modified to assist in extracting acidic or basic compounds. 

M. Demovics, Z. Stefanka, P. Fodor, Improving selenium extraction by sequential enzymatic processes for Se-speciation of selenium-enriched Agaricus bisporus, Anal. Bioanal. Chem., 372 (2002), 473D480. 

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