Total Dissolution

Elemental analysis of organie and inorganie samples requires partial or total dissolution of the sample prior to speetrometrie analysis. Mierowave-assisted extraetion (MAE) provides an alternative to traditional digestion methods and it is reeognized as one of the most effieient methods for the dissolution of soil samples. 

Quantitative analysis of multicomponent additive packages in polymers is difficult subject matter, as evidenced by results of round-robins [110,118,119]. Sample inhomogeneity is often greater than the error in analysis. In procedures entailing extraction/chromatography, the main uncertainty lies in the extraction stage. Chromatographic methods have become a ubiquitous part of quantitative chemical analysis. Dissolution procedures (without precipitation) lead to the most reliable quantitative results, provided that total dissolution can be achieved follow-up SEC-GC is molecular mass-limited by the requirements of GC. Of the various solid-state procedures (Table 10.27), only TG, SHS, and eventually Py, lead to easily obtainable accurate quantitation. 

Since m is the mass of solid remaining at time t, the quantity m/m0 is the fraction undissolved at time t. The time to total dissolution (m/m0 = 0) of all the particles is easily derived. Equation (49) is the classic cube root law still presented in most pharmaceutics textbooks. The reader should note that the cube root law derivation begins with misapplication of the expression for flux from a slab (Cartesian coordinates) to describe flux from a sphere. The error that results is insignificant as long as r0 8. 

Johnson and Swindell [77] developed a method for evaluating the complete particle distribution and its effect on dissolution. This method divided the distribution into discrete, noncontinuous partitions, from which Johnson and Swindell determined the dissolution of each partition under sink conditions. The dissolution results from each partition value were then summed to give the total dissolution. Oh et al. [82] and Crison and Amidon [83] performed similar calculations using an expression for non-sink conditions based on a macroscopic mass balance model for predicting oral absorption. The dissolution results from this approach could then be tied to the mass balance of the solution phase to predict oral absorption. 

Skin is unstable to varying environmental conditions and deteriorates readily under humid conditions or through biological activity, or both. Basically, the decay of much ancient skin and hide results from hydrolysis, that is, the reaction of the protein fibers in the skin with water in extreme cases, the hydrolysis of skin and hide may cause their total dissolution, and quite often, under humid and hot environmental conditions, nothing remains to indicate that skin or hide was once there. 

ABSTRACT The results of a soil geochemical survey of the Canadian Maritime provinces and the northeast states of the United States are described. The data presented are for the <2-mm fraction of the surface layer (0-5 cm depth) and C horizons of the soil. Elemental determinations were made by ICP-MS following two digestions, aqua regia (partial dissolution) and a strong 4-acid mixture (near-total dissolution). The preliminary results show that Hg and Pb exhibit elevated abundances in the surface layer, while As and Ni exhibit abundances that can be attributed to the geological provenance of the soil parent materials. 

The freeze-dried sediments were subjected to both a total dissolution and a selective extraction. The latter, as described in Chester Hughes (1967), is carried out in a hydroxylamine hydrochloride and acetic acid (HA) solution and designed to isolate reactive phases. With the exception of total Se, extracted metals were determined by the method described for porewaters. Total solid Se concentrations were measured by AAS with HG-FIAS (analysis ongoing). 

Obviously, the technology exists for obtaining analytical results without special preparation and analysis in a laboratory. However, at the present time there is no acceptable substitute for direct laboratory examination of samples if we want the kind of accuracy and confidence we have come to expect. All conventional methods for analysis of solid materials require one or more of the following preparation activities before an analytical method can be properly executed 1) particle size reduction, 2) homogenization and division, 3) partial dissolution, and 4) total dissolution. Let us briefly discuss each of these individually. 

In the event that extraction is not useful or feasible, total dissolution of a sample may be required. Total dissolution involves the proper choice of solvent—one that will indeed dissolve the total sample. For solid samples, this will usually involve the use of water or acid-water mixtures, sometimes fairly concentrated acid solutions. For this reason, it is useful to summarize the application of water and the most common laboratory acids ... 

Bis(l-pyrazolyl)methane (bpm) can be prepared by the method of Elguero and co-workers, or by the procedure reported more recently by Jameson and Castellano. Solid bpm is added (2.96 g, 20 mmol) to a stirred solution of [Ni (0H2)6](N03)2 (2.91 g, 10 mmol) dissolved in 100 mL of water. Total dissolution of the bpm occurs after 15 min, resulting in a deep blue solution. Slow evaporation of the solution over several days gives blue crystals of the product. The crystals are filtered, washed with a small amount of water and diethyl ether, and dried in air. Yield 4.3 g, 84%. 

Figure 2 shows the extent of dissolution of red spruce in methylamine, the amount of precipitate collected in the first trap upon complete depressurization to 1 bar, and the Klason lignin content in the wood residue after extraction, as functions of extraction time. The total dissolution and precipitation are normalized with respect to oven dry weight of initial wood. The extraction conditions were 185°C, 275 bar, and 1 g/min solvent flow rate. As shown in the figure, dissolution initially increases with time and levels off at about 28% by weight. The precipitates which were collected as solids follow a similar trend. The Klason lignin content of the wood residue decreases with extraction time, from an initial value of 26.5% down to 10.1% after 5 h of extraction. 

At present, the binary water-soluble preparation of heparin and proteolytic enzymes is being applied for the treatment of thromboses. For instance, injection into the bloodstream of heparin-plasmin complex or a heparin-plasmin-streptokinase preparation leads to the total dissolution of the thrombus, while if introduced separately, heparin and streptokinase do not display the lytic action at all, and plasmin, alone or together with streptokinase, dissolves the thrombus only partially 132>. The treatment of acute thrombophlebitis with trypsin resulted in a full dissolution of the thrombus and in an increase of antithrombin III in the blood 133). Administration of trypsin together with heparin has an effect similar in efficiency to the action of the heparin-plasmin complex 134>. The use of a mix of heparin and urokinase for improving tbrom-boresistance of polymeric materials was also described 13S). These substances were immobilized by preliminary coating of the surface of a polymer with a graphite layer and subsequent adsorption of heparin and the enzyme. 

Figure 10. Mechanisms of glass corrosion for a soda-silica glass. Conditions a, t = 0, pH = 7 b (stage 1), t > 0, pH < 9, selective Na dissolution and c (stage 2), t 0, pH 9 total dissolution. (Reproduced, with permission, from Ref. 1. Copyright 1979, Books for Industry.)...

Copper powder (0.4g, 0.006mol), N-methylformamide (6mL), and CC14 (12mL) were placed in a flask and the mixture heated to 70°C, refluxed, and stirred until total dissolution of copper was observed (2 hr). The green solution was filtered and allowed to stand at room temperature for 3 days, after which turquoise long needles of [CH3NH3][Cu(HCOO)3] separated. These were filtered out, washed with a mixture of EtOH and Et20, and finally dried at room temperature. Yield 1.07 g (72%). 

Inorganic samples, soils, sediments, ores, rocks, and minerals may be digested in dilute or concentrated acids or mixtures of acids, which may be sufficient to leach out the analytes. However, if total dissolution is required,... 

Betzer et al. (1984, 1986) studied the sedimentation of pteropods and foraminifera in the North Pacific. Their sediment trap results confirmed that considerable dissolution of pteropods was taking place in the water column. They calculated that approximately 90% of the aragonite flux was remineralized in the upper 2.2 km of the water column. Dissolution was estimated to be almost enough to balance the alkalinity budget for the intermediate water maximum of the Pacific Ocean. It should be noted that the depth for total dissolution in the water column is considerably deeper than the aragonite compensation depth. This is probably due to the short residence time of pteropods in the water column because of their rapid rates of sinking. 

Step 4a. For microwave-assisted, digestion, follow the procedure developed for the microwave system in the laboratory. Note that total dissolution of the solid is required for radioanalytical chemistry, whereas partial dissolution is acceptable for other analytical processes if the method has been tested for fractional recovery. Several references are given below that may be helpful in developing or using this method. 

R. Garcia and B. Kahn, Total Dissolution of Environmental and Biological Samples by Closed-Vessel Microwave Digestion for Radiometric Analysis, J. Radioanalytical and Nuclear Chemistry 250, 85-91 (2001). 

In the peak experience that MMDA may elicit, it is possible to speak of both individuality and dissolution, but these are blended into a quite new totality. Dissolution is here expressed in the openness to experience, a willingness to hold no preference individuality, on the other hand, is implied in the absence of depersonalization phenomena, and in the fact that the subject is concerned with the everyday world of persons, objects, and relationships. 

Hydroxyapatite is not stable in the presence of chelating agents and at pH below 5 Both phenomena contribute to the degradation of the mineral structure and to partial or total dissolution of the crystals. 

Another method of synthesis involves the direct reaction of stoichiometric amounts of ligand in acid form and lanthanide oxide, hydroxide or carbonate in suspension in hot water. The mixture is heated under reflux until total dissolution is obtained. 

As noted earlier, some of the steps that precede the insertion of the treated sample into the instrument for measurement (e.g. dissolution, clean-up, preconcentration, individual separation, derivatization) can have a critical influence on accuracy and precision depending on the particular step. All analytical processes include a sample preparation step which is a function of a number of factors such as the physical state of the sample, the nature of the sample matrix and analytes or the type of detector, for example. The first distinction therefore refers to the nature of the sample solid, liquid or gas. Solid samples are the most difficult to process as most analytical instruments cannot handle them. Therefore, the first operation in solid sample preparation involves transferring the target analytes to a liquid phase. This can be carried out in various ways including total dissolution of the test sample or partial dissolution or separation of a portion thereof. The different choices, which can be assisted by ultrasound, are depicted in Fig. 2.2, and discussed in the following sections. 

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