Chemical quantitative study

Campo, E., Ferreira, V., Escudero, A., Marques, J. C., and Cacho, J. (2006). Quantitative gas chromatography-olfactometry and chemical quantitative study of the aroma of four Madeira wines. Anal. Chim. Acta 563,180-187. 

A good introduction to XRF instrumentation, qualitative and quantitative analyses, and chemical-bonding studies. 

These observations remind us of Chapter 8, in which we considered the factors that determine the rate of a chemical reaction. Of course, the same ideas apply here. We can draw qualitative information about the mechanism of the reaction by applying the collision theory. With quantitative study of the effects of temperature and concentration on the rate, we should be able to construct potential energy diagrams like those shown in Figure 8-6 (p. 134). 

With growing interest in the chemical behaviour of actinide ions in the environment (1), the complexation of these ions with carbonate anions has been recently attracting particular attention (2-10) due to the ubiquitous presence of carbonate ions in nature (11, 12) and their pronounced tendency to form complexes with heavy metal ions (7, 10-14). In spite of the carbonate complexation of actinides being considered important chemical reactions for understanding the chemistry of actinides in natural fluids, not many experiments have been devoted up to now to the quantitative study of the subject, though numerous qualitative observations are discussed in the literature. Although there are a few papers reporting the formation constants of carbonate complexes... 

Street JC, Sharma RP. 1975. Alteration of induced cellular and humoral immune responses by pesticides and chemicals of environmental concern Quantitative studies of immunosuppression by DDT, Aroclor 1254, carbaryl, carbofuran, and methyl parathion. Toxicol Appl Pharmacol 32 587-602. 

Measurement of exposure can be made by determining levels of toxic chemicals in human serum or tissue if the chemicals of concern persist in tissue or if the exposure is recent. For most situations, neither of these conditions is met. As a result, most assessments of exposure depend primarily on chemical measurements in environmental media coupled with semi-quantitative assessments of environmental pathways. However, when measurements in human tissue are possible, valuable exposure information can be obtained, subject to the same limitations cited above for environmental measurement methodology. Interpretation of tissue concentration data is dependent on knowledge of the absorption, excretion, metabolism, and tissue specificity characteristics for the chemical under study. The toxic hazard posed by a particular chemical will depend critically upon the concentration achieved at particular target organ sites. This, in turn, depends upon rates of absorption, transport, and metabolic alteration. Metabolic alterations can involve either partial inactivation of toxic material or conversion to chemicals with increased or differing toxic properties. 

The application of NMR to the study of chemical reactions has been expanded to a wide range of experimental conditions, including high pressure and temperatures. In 1993, Funahashi et al. [16] reported the construction of a high pressure 3H NMR probe for stopped-flow measurements at pressures <200 MPa. In the last decade, commercial flow NMR instrumentation and probes have been developed. Currently there are commercially available NMR probes for pressures of 0.1-35 MPa and temperatures of 270-350 K (Bruker) and 0.1-3.0 MPa and 270-400 K (Varian). As reported recently, such probes can be used to perform quantitative studies of complicated reacting multicomponent mixtures [17]. 

Chemical kinetics deals with quantitative studies of the rates at which chemical processes occur, the factors on which these rates depend, and the molecular acts involved in reaction processes. A description of a reaction in terms of its constituent molecular acts is known as the mechanism of the reaction. Physical and organic chemists are primarily interested in chemical kinetics for the light that it sheds on molecular properties. From interpretations of macroscopic. kinetic data in terms of molecular mechanisms, they can gain insight into the nature of reacting systems, the processes by which chemical bonds are made and broken, and the structure of the resultant product. Although chemical engineers find the concept of a reaction mechanism useful in the correlation, interpolation, and extrapolation of rate data, they are more concerned with applications... 

Mechanisms of dissolution kinetics of crystals have been intensively studied in the pharmaceutical domain, because the rate of dissolution affects the bioavailability of drug crystals. Many efforts have been made to describe the crystal dissolution behavior. A variety of empirical or semi-empirical models have been used to describe drug dissolution or release from formulations [1-6]. Noyes and Whitney published the first quantitative study of the dissolution process in 1897 [7]. They found that the dissolution process is diffusion controlled and involves no chemical reaction. The Noyes-Whitney equation simply states that the dissolution rate is directly proportional to the difference between the solubility and the solution concentration ... 

Olea, D. and Faure, C. (2003) Quantitative study of the encapsulation of glucose oxidase into multilamellar vesicles and its effect on enzyme activity. Journal of Chemical Physics, 119, 6111-6118. 

Methods have been presented, with examples, for obtaining quantitative structure-property relationships for alternating conjugated and cross-conjugated dienes and polyenes, and for adjacent dienes and polyenes. The examples include chemical reactivities, chemical properties and physical properties. A method of estimating electrical effect substituent constants for dienyl and polyenyl substituents has been described. The nature of these substituents has been discussed, but unfortunately the discussion is very largely based on estimated values. A full understanding of structural effects on dienyl and polyenyl systems awaits much further experimental study. It would be particularly useful to have more chemical reactivity studies on their substituent effects, and it would be especially helpful if chemical reactivity studies on the transmission of electrical effects in adjacent multiply doubly bonded systems were available. Only further experimental work will show how valid our estimates and predictions are. 

Ab initio quantum mechanical methods are needed to semi quantitatively study chemical reactions involving bond breaking and bond forming phenomena. Once a reaction path for a chemical process is defined, it is possible to obtain the key transition geometries and associated energies of... 

The observation of the induced emission, its time behavior and threshold conditions allow to study with new techniques details of chemical reactions which lead to specific states of the molecular or atomic reaction product A quantitative study of such laser systems will also yield information about collisional deactivation rates of the excited states (see also Section 111.4). 

The problem of chemical composition was directly related to that of chemical combination. Combining chemicals to produce new substances had been a goal of individuals throughout history. Lavoisier s work emphasized the quantitative study of chemical combination. Chemists sought to determine the proportion in which chemicals combined, and how much of one substance it took to react with another. Rather than combining substances using the alchemist s trial and error method, chemists sought to determine the specific ratio of chemicals involved in chemical reactions. 

Temperature, pH, ionic strength, concentration of a metal ion, and other environmental parameters influence a chemical reaction and varying their values can signify drastic changes, depending on the case, on the rate, mechanism, or direction of the reaction. For this reason quantitative studies on the effects of physical parameters on reactivity often take a very long time in this kind of research. 

Impurities in API. Treatment of the impurities in the API is similar to that for the new drug product. Impurities in the API include organic impurities (process and drug related), inorganic impurities, and residual solvents. Quality control analytical procedures are developed and validated to ensure appropriate detection and quantitation of the impurities. Specification limits for impurities are set based on data from stability studies and chemical development studies. A rationale for the inclusion or exclusion of impurities is set at this stage. The limits set should not be above the safety level or below the limit of the manufacturing process and analytical capability. 

As summarized above, by using polymer-metal complexes of uniform structure, much progress has already been achieved in the quantitative study of the relationship between the chemical function and the effects of a polymer chain, in comparison with previous studies in the fields of other polymeric chemical reagents organic... 

Bioenergetics is the quantitative study of the energy transductions that occur in living cells and of the nature and function of the chemical processes underlying these transductions. Although many of the principles of thermodynamics have been introduced in earlier chapters and may be familiar to you, a review of the quantitative aspects of these principles is useful here. 

Quantitative studies using LSV and CV can be carried out for both heterogeneous charge transfer kinetics and the kinetics of homogeneous chemical reactions coupled to charge transfer at electrodes. These methods should continue to play a major role in the study of electron transfer reactions. 

The behavior of it1/2 as a function of time can be influenced substantially by the presence of chemical reactions that are coupled to the electrode process (see Chap. 2). Consequently, characteristic variations of it1/2 versus t have been effectively utilized for the quantitative study of such homogeneous chemical reactions. The ECE reaction in which a chemical step exists between two electron transfer steps is one mechanism that has been investigated by means of chronoamperometry ... 

The formula in Figure 3.2c shows that the larger the shift difference (Vab) between the exchanging signals, the larger the rate constant needed to get coalescence at a specific temperature. Thus, since chemical shift differences in 13C NMR are usually much larger (in Hz) than in ]H NMR, 13C NMR spectroscopy permits the quantitative study of much faster processes than can be investigated by 1H NMR spectroscopy. 

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