Aqueous-extract conductivity test

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. 

Aqueous solution conductivity is an IPC test used to determine the removal of dissolved ionic impurities (salt) from filter cakes and extractions of product-rich organic phases.The initial water conductivity ( S/cm) is used as the basis for the criteria for IPC. The end point for washes is usually established at a level when the conductivity of the final aqueous extraction(s) and wet cake wash solutions are close to the initial conductivity of the prewash water. 

J.9 You are asked to identify compound X, which was extracted from a plant seized by customs inspectors. You run a number of tests and collect the following data. Compound X is a white, crystalline solid. An aqueous solution of X turns litmus red and conducts electricity poorly, even when X is present at appreciable concentrations. When you add sodium hydroxide to the solution a reaction takes place. A solution of the products of the reaction conducts electricity well. An elemental analysis of X shows that the mass percentage composition of the compound is 26.68% C and 2.239% H, with the remainder being oxygen. A mass spectrum of X yields a molar mass of 90.0 g-moF. (a) Write the empirical formula of X. (b) Write... 

In screening tests, it is common practice to use approximately 0.1 mol dm or 5 vol% solutions of extractant, and extraction tests are conducted at a phase ratio of 1, with a 5 min contact time. These conditions, of course, may be varied, but the object is to stay with as simple an approach as possible. Analysis of only the aqueous raffinate need be carried out, and distribution data calculated from this. 

The tubes were gently agitated at constant temperature and sacrificed at regular time intervals. Each tube was centrifuged and the bulk of the water phase separated from the sediment phase. The aqueous and sediment phases were then separately analyzed for the remaining concentrations of parent compound. Careful tests were conducted to assure complete extraction of the compound from the two phases ( 10). Thus, the concentrations remaining in each phase could be separately determined as a function of time. 

Three basic approaches have been employed to conduct the TBA test on foods. It can be performed (1) on aqueous acid extracts of food samples (see Basic Protocol 1 Tarladgis et al., 1964 Witte et al., 1970 Siu and Draper, 1978 Caldironi and Bazan, 1982 Salih et al., 1987 Bedinghaus and Ockerman, 1995), (2) on an aliquot of a steam distillate of food samples (see Alternate Protocol 1 Tarladgis et al., 1960 Igene et al., 1979 Yamauchi et al., 1982 Ke et al., 1984), and (3) on the extracted lipid portion of food samples (see Alternate Protocol 2 You-nathan and Watts, 1960 Pikul etal., 1983). The chromophore formed by the reaction of malonaldehyde with TBA is then quantified spectro-photometrically. 

A procedure was developed for the determination of total and labile Cu and Fe in river surface water. It involved simultaneous solvent extraction of the metals as diethyldithio-carbamates (ddc) and tfac complexes. The complexes were extracted by isobutyl methyl ketone (ibmk) and the solution subjected to flame atomic absorption spectrometry. Variables such as pH, metal complex concentration, reaction time, ibmk volume and extraction time were optimized. Prior to the solvent extraction a microwave-assisted peroxydisulfate oxidation was used to break down the metallorganic matter complexes in the river surface waters . Trifluoroacetylacetone was used as a chelation agent for the extraction and quantitative determination of total Cr in sea water. The chelation reaction was conducted in a single aqueous phase medium. Both headspace and liquid phase extractions were studied and various detection techniques, such as capillary GC-ECD, EI-MS (electron-impact MS) and ICP-MS, were tested and compared. The LOD was 11-15 ngL Cr for all the systems examined. The method provided accurate results with EI-MS and ICP-MS, while significant bias was experienced with ECD °. ... 

An efficient solution for the subtraction method was proposed by Bassette and Whit-nah [16]. The reactions were conducted in a system containing two phases water and carbon tetrachloride. The test mixture, which consisted of an aqueous solution of organic compounds, was used as one of the two phases (aqueous). After shaking and separation of the layers, the carbon tetrachloride was analysed with the extracted compounds by GC (see Fig. 5.3A). 

Using liquid/liquid phase separation by thenoyltrifluoracetone, TTA, in benzene, the authors studied the speciation of Zr in the concentration range 10 to 0.1 M in 2 M perchloric acid solution as well as in 1 M HCIO4/I M LiC104 solutions. TTA is known to selectively extract free tetravalent ions such as Zr or the tetravalent actinide ions. Polymer formation by Zr in the aqueous phase is reflected quantitatively as a decrease in the distribution coefficient. The experiments were conducted very carefully spectroscopic determination of species in the benzene phase, correction for TTA loss of the benzene phase, consideration for complexation of Zr by TTA in the aqueous phase, recrystallisation of starting solids, consideration of impurities in the test, assurance that equilibrium has been reached and discussion of errors related to the variation of proton activity in the aqueous phase due to the extraction reaction. 

Several studies have been conducted on the stability of selected plastics additives for food contact in EU aqueous, fatty and alternate stimulants. Thus, Simoneau and Hannaert [17] showed that bis(2-ethylhxyl)phthalate plasticiser and octadecyl 3-(3,5-di-ter -butyl 4-hydroxy phenyl) propionate antioxidant are quite stable under all heat exposure conditions tested (20-40 °C, 1 h to 10 days) and all food simulents used (15% ethanol, 95% ethanol, 3% acetic acid, olive oil and iso-octanol). In these tests, the amounts of additives remaining in the plastic at the end of the test were between 90% and 107% of the amounts present in the plastic before extraction. 

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