Single extraction mobile

Despite these shortcomings, common to any chemical extraction procedure, sequential dissolution techniques still furnish more useful information on metal binding, mobility and availability than can be obtained with only a single extractant. 

In addition, the overall content of TEs in extractable (mobile) forms can be estimated prior to SEP by a single-extraction procedure using electrolyte solutions, such as 1.0 mol HNO3 or 1.0 mol L HCl (Ladonin, 2002). If the contents of TEs obtained by the screening protocol are rather low, it might then be unreasonable to use a sequential extraction method. 

The diversity and complexity of the available approaches has identified the major difficulties associated with producing suitable guidelines that would allow comparisons between different laboratories and different countries in assessing metal mobility in the soil environment. This led to the development of single and sequential extraction procedures by the Standards, Materials and Testing (SM T - formerly the (European) Community Bureau of Reference (BCR) Programme of the European Union (1987)). Single extractants evaluated included 0.05 moll-1 EDTA, 0.43 moll-1 acetic acid, and 1 moll-1 ammonium acetate at pH 7. 

Since most APIs have some aqueous solubility, extraction is typically performed at room temperature with aqueous or a mixture of aqueous and organic media.Extraction can be performed in one step with a single solvent or in multiple steps executed sequentially with different solvents. The extraction solvent must be able to solubilize the API and be compatible with the HPLC mobile phase for the final analysis. The pH, buffer concentration and organic solvent composition of the extraction... 

This case study illustrates the SP method development of an assay method for a controlled-release analgesic tablet with a single API. Certain considerations were taken into account. First, the analyte within the tablet matrice core had to be extracted quantitatively. Second, the analyte was diluted into a final solution that was compatible with the HPLC mobile phase. Third, short SP time was required (i.e., 30 min) to maximize productivity of the work scheme for processing a large number of samples. 

A completely automated system with reinjection/sample collection and solvent recovery allows the separation of up to 10 g of extract a day. The Cjq is obtained in very high purity and the recovery is nearly 100%. A simple benchtop method for the enrichment of preparative amounts of Cjq, C7Q and higher fullerenes (up to Cjqq) from a crude fullerene mixture is based on a single elution through a column of poly(dibromostyrene)-divinylbenzene using chlorobenzene as mobile phase [208]. 

More recently, some studies have reported the use of supercritical fluid chromatography (SEC) [479,480], Coupling SEC with SEE, sample extraction, preconcentration, and quantification can be performed in a single step. The mobile phase, carbon dioxide, can be modified by adding different... 

Data for step-mobilities shown in Fig. 6 span an impressively large range a factor of 10 " separates step-mobilities measured by STM from the step-mobilities extracted from the relaxation of micron-sized gratings. Some discrepancies exist, but most of the step-mobilities are consistent with a single activation energy of 1.8 eV and an attempt rate given by the frequency of atomic vibrations. We hope that this initial comparison of step-mobility data will help motivate more detailed theoretical analysis and experiments on the coimections between step-mobility and the evolution of surface morphology. 

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