Organic quantitative determination

Carius method The quantitative determination of S and halogens in covalent (organic) compounds by complete oxidation of the compound with cone, nitric acid and subsequent estimation of precipitated AgX or BaS04. 

It must be stressed that the identification of the causative organism(s) may be extremely difficult since it often depends on the quantitative determination of numbers of each microbial type in a complex mixture together with an assessment of its chemical and physical activities in that particular environment. 

Ion chromatography permits the determination of both inorganic and organic ionic species, often in concentrations of 50 g L"1 (ppb) or less. Since analysis time is short (frequently less than 20 minutes) and sample volumes may be less than 1 mL, IC is a fast and economical technique. It has found increasing application in a number of different areas of chemical analysis and particularly for the quantitative determination of anions. The state-of-the-art has been reviewed.26... 

As with electronic spectra, the use of infrared spectra for quantitative determinations depends upon the measurement of the intensity of either the transmission or absorption of the infrared radiation at a specific wavelength, usually the maximum of a strong, sharp, narrow, well-resolved absorption band. Most organic compounds will possess several peaks in their spectra which satisfy these criteria and which can be used so long as there is no substantial overlap with the absorption peaks from other substances in the sample matrix. 

The analysis of phosphates and phosphonates is a considerably complex task due to the great variety of possible molecular structures. Phosphorus-containing anionics are nearly always available as mixtures dependent on the kind of synthesis carried out. For analytical separation the total amount of phosphorus in the molecule has to be ascertained. Thus, the organic and inorganic phosphorus is transformed to orthophosphoric acid by oxidation. The fusion of the substance is performed by the addition of 2 ml of concentrated sulfuric acid to — 100 mg of the substance. The black residue is then oxidized by a mixture of nitric acid and perchloric acid. The resulting orthophosphate can be determined at 8000 K by atom emission spectroscopy. The thermally excited phosphorus atoms emit a characteristic line at a wavelength of 178.23 nm. The extensity of the radiation is used for quantitative determination of the phosphorus content. 

AES is a useful element-specific technique for quantitative determination of the elemental composition of a surface. Although some chemical information is available in principle, the technique is used largely for elemental analysis. Electron beam damage can decompose organic adsorbates and cause damage, particularly on insulating surfaces. In some cases, the beam can reduce metal oxides. 

GC is extensively used to determine phenolic and amine antioxidants, UV light absorbers, stabilisers and organic peroxide residues, in particular in polyolefins, polystyrene and rubbers (cf. Table 61 of Crompton [158]). Ostromow [159] has described the quantitative determination of stabilisers and AOs in acetone or methanol extracts of rubbers and elastomers by means of GC. The method is restricted to analytes which volatilise between 160 °C and 300 °C without decomposition. A selection of 47 reports on GC analysis of AOs in elastomers (period 1959-1982) has been published... 

Table 2 Summary of some representative current analytical methods for quantitative determination of selected priority and emerging organic contaminants in environmental samples. Adapted from [7]... 

However, the main use of fluorescence has been in the semi-quantitative determination of aromatic hydrocarbons by extraction into an organic solvent, followed by excitation at a standard wavelength and comparison with the emission from a chosen standard. These techniques have been studied by many workers [38-42],... 

The determination of dissolved organic carbon by oxidation methods in water comprises three analytical steps the removal of inorganic carbon from the sample, oxidation of the organic compounds to carbon dioxide, and the quantitative determination of the resulting carbon dioxide. The methods of oxidation can be classified into three major groups ... 

For several reasons, it is very difficult to quantitatively determine the solubility of an organic pigment as related to the particle size. F. Glaser [25] found that a particle diameter of 0.3 pm represents somewhat of a threshold value. The solubility of pigment crystals above this size essentially equals that of very large particles (cx) and is therefore largely constant in moving towards finer particle sizes, however, the solubility increases appreciably (Table 7). 

The detection system should assist in the structural elucidation of unknown organic compounds. Moreover, accurate quantitative determinations should be feasible. 

As esters the alkyl halides are hydrolysed by alkalis to alcohols and salts of halogen acids. They are converted by nascent hydrogen into hydrocarbons, by ammonia into amines, by alkoxides into ethers, by alkali hydrogen sulphides into mercaptans, by potassium cyanide into nitriles, and by sodium acetate into acetic esters. (Formulate these reactions.) The alkyl halides are practically insoluble in water but are, on the other hand, miscible with organic solvents. As a consequence of the great affinity of iodine for silver, the alkyl iodides are almost instantaneously decomposed by aqueous-alcoholic silver nitrate solution, and so yield silver iodide and alcohol. The important method of Ziesel for the quantitative determination of alkyl groups combined in the form of ethers, depends on this property (cf. p. 80). 

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