Dissolving samples inorganic solids

Wastewater contains a wide variety of suspended solid materials. The classification of the various solids is shown in Figure 8.3. Total solids are obtained by evaporating a sample of wastewater to dryness at 103-105°C. A filtration step separates the total suspended solids (TSS), which remain on the filter, from the total dissolved solids (TDS), which pass in the filtrate. The residue that remains after the TS are ignited at 500° C is called the total fixed solids (TFS), and they represent the inorganic salts in the sample. The solids that are volatilized... 

The present book describes the traditional methods of qualitative inorganic analysis. These can be divided broadly into two categories dry tests which are carried out on solid samples, usually at higher temperatures and, more commonly, wet reactions involving dissolved samples and reagent solutions. The chemical change (or its absence) is observed and used for the elucidation of sample composition. 

Most conventional quantitative analyses are best suited for the analysis of liquid samples. Because of this, solid samples that are to be analy2 ed are typically dissolved in a suitable solvent The solvent chosen may be either polar (e. g. water) or non-polar (e. g. benzene) depending on the polarity and reactivity of the sample. In order to ensure that the entire analyte has been dissolved, a solvent is chosen that can dissolve the entire solid sample (analyte as well as other materials). If the sample cannot be readily dissolved in these mild conditions, many other techniques are available for dissolution. As inorganic materials often represent the greatest difficulty in dissolution, this section will deal primarily with these materials. 

Distribution box Serves to distribute the flow from the septic tank evenly to the absorption field or seepage pits. It is important that each trench or pit receive an equal amount of flow. This prevents overloading of one part of the system. Dissolved solids Chemical substances either organic or inorganic that are dissolved in a waste stream and constitute the residue when a sample is evaporated to dryness. 

Sample preparation for the common desorption/ionisation (DI) methods varies greatly. Films of solid inorganic or organic samples may be analysed with DI mass spectrometry, but sample preparation as a solution for LSIMS and FAB is far more common. The sample molecules are dissolved in a low-vapour-pressure liquid solvent - usually glycerol or nitrobenzyl alcohol. Other solvents have also been used for more specialised applications. Key requirements for the solvent matrix are sample solubility, low solvent volatility and muted acid - base or redox reactivity. In FAB and LSIMS, the special art of sample preparation in the selection of a solvent matrix, and then manipulation of the mass spectral data afterwards to minimise its contribution, still predominates. Incident particles in FAB and LSIMS are generated in filament ionisation sources or plasma discharge sources. 

If solid samples are insoluble in water, some decomposition procedure must be used. For inorganic materials, decomposition with mineral acids is most often employed (for a survey of decomposition techniques see [33]). When the sample cannot be dissolved in an acid, it can either be fused (most often with alkali carbonates, hydroxides or their mixtures [157, 47]) or sintered (usually with mixtures of alkali carbonates with divalent metal oxides, sometimes in the presence of oxidants [54]). Sintering is usually preferable, because then contamination of the sample and the resultant ionic strength are lower than is the... 

Substances that will not dissolve in acid can usually be dissolved by a hot, molten inorganic flux (Table 28-6). Finely powdered unknown is mixed with 2 to 20 times its mass of solid flux, and fusion (melting) is carried out in a platinum-gold alloy crucible at 300° to 1 200°C in a furnace or over a burner. The apparatus in Figure 28-9 fuses three samples at once over propane burners with mechanical agitation of the crucibles. When the samples are homoge-... 

The major disadvantage of solid phase extraction is that it provides a chemically biased view of the DOM reservoir, and seems to preferentially extract compounds with relatively low amounts of N. Other problems include sample contamination by various resins and incomplete elution of adsorbed DOM. SoHd phase extraction remains, however, the only technique capable of reproducibly isolating DOM compounds within the entire range of MWs. Furthermore, the radiocarbon content (A " C) of DOC isolated by XAD resins is depleted relative to the total dissolved inorganic carbon (DIG) reservoir values for XAD isolates are between —300... 

Samples from Sigh Island 573 field (Mobil Oil) except sample 83-TX-12, which is from High Island 571 field (Columbia Gas). Depth is that of midpoint of perforation below sea level (depth of water column is -Temp, is the measured subsurface temperature. TDS = mg L total dissolved solids. Aik is field-titrated alkalinity as HC03 and comprises organic as well as inorganic species. 

Specific conductance, pH, and DOC concentrations also were distinctly different between stream-water and collapsed-foam samples from each site. Foams possessed a 10 to 20-fold increase in DOC content compared to stream-water samples combined with a higher calculated dissolved solids content and lower pH than their host stream. This indicates that the foams are apparently a concentration medium for both inorganic matter and organic acids. 

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