Dilution principle

Rossa, L., Vogtle, F. Synthesis of Medio- and Macrocyclic Compounds by High Dilution Principle Techniques, 113, 1-86 (1983). 

The isotope dilution principle, first employed by Hevesy and Hobbie (133) in 1932 for the determination of lead in ores, was applied by Schoenheimer et al. (241) to the determination of amino acids. [Shemin and Foster (248) have reviewed this topic.] An N15-amino acid derivative was added to a protein hydrolyzate, a sample of the amino acid to be determined was isolated and purified, the excess N15 in this product was estimated with the mass spectrograph, and the grams of amino acid originally present were calculated from Equation 2. 

The homocyclic sulfur oxide SsO was prepared by condensation of thionylchloride with crude sulfane oil at -40 °C applying the dilution principle. It is believed that the product results from the heptasulfane content of the sulfane oil [88] ... 

CycZo-Octasulfurmonoxide was the first homocyclic sulfuroxide prepared as a pure material. Originally it had been prepared in 1972 by condensation of thionyl chloride and heptasulfane [69, 70]. The two components, dissolved in CS2, were added to a mixture of CS2 and Me20 at -40 °C applying the dilution principle ... 

A most important technique which has been developed as an extension of the isotope dilution principle is that of radioimmunoassay (RIA). Analyses by this method employ substoichiometric amounts of specific binding immuno-chemical reagents for the determination of a wide range of materials (immunogens) which can be made to produce immunological responses in animals such as sheep or rabbits. It is possible to combine the specificity of an immunochemical reaction with the extreme sensitivity of radiotracer detection. Analytical methods based upon these principles have achieved wide applicability in the determination of organic compounds at trace levels. 

This demonstration is intended to show how quantification is achieved using isotope dilution principles in mass spectrometry (Fig. 14.5). It also shows the issue of error in clinical measurements, such as precision accuracy and the use of relative relationships of one compound to another. 

Rossa, L. and Vogtle, F Synthesis of medio- and macrocyclic compounds by high dilution principle techniques, Top. Curr. Chem., 113, 1 (1983). 

The effident synthesis of macrocycles generally requires the use of high dilution conditions in order to depress the formation of oligomers and polymers with respect to the monomer ( High Dilution Principle ) (52, 53). 

The reactions of 1,2,2-trifunctional disilanes with triethanolamine, using the Dilution principle , result in the formation of compounds 212-214 (equation 195)420 which are the silyl analogs of 2-carba-3-oxahomosilatranes (94). 

The sample dilution principle employed in the pT-scale improves the determination of toxic hazard potentials of sediment samples over that of effect percentages reported for undiluted test samples. For instance, a 100% effect measured with a specific endpoint and produced by undiluted samples may become undetectable after a dilution of 1 2 or after much higher dilutions. Clearly, it is essential to know the dilution level at which a whole sediment (or one of its liquid phases) ceases to be toxic1. In this respect, the pT-dilution approach offers valuable information allowing sediments to be more accurately classified in terms of the magnitude of toxicity. 

From Equation 6.19 it follows that the lower the concentration of the activated acid, the higher the selectivity with which the lactone is produced versus the acyclic ester, oligo- and polyesters. Macrolactones are therefore produced in very dilute (<1 /xmol/L) solutions (high dilution principle according to Ziegler and Ruggli). 

Note the general principle that can be drawn from this As the total concentration of a self-associating molecule increases, the proportion of the associated form increases, A corollary is that dilution favors the monomeric species. This is an example of Ostwald s dilution principle. 

The concept of concentration addition (CA) looks at mixture effects of chemicals in terms of a dilution principle. It assumes that 1 chemical can be replaced totally or in part by an equal fraction of an equi-effective concentration of another (hence the term similar action ), without diminishing the overall combined effect (Loewe and Muischneck 1926). If the assumption of CA holds true, these fractions of equi-effective concentrations, which are also called toxic units, sum up to a value of 1—thus the name dose or concentration addition. CA implies that every chemical in any concentration contributes to the overall toxicity of a mixture. Whether the individual doses are also effective alone does not matter. Thus, combination effects should also result from chemicals at or below effect thresholds, provided sufficiently large numbers of components sum up to a sufficiently high total effect dose. 

Experimental evaluations of combination effects at the cellular or subcellular level from suspected endocrine disruptors or mycotoxins have demonstrated the usefulness of CA (Speijers and Speijers 2004 Kortenkamp 2007). However, on the grounds of theoretical considerations, this may not be surprising. For biological responses at the molecular level, for example, enzyme activities or receptor interactions, the dilution principle that is at the heart of CA can be readily interpreted in terms of molecular interactions. For this reason, other than concentration-additive effects may be difficult to envisage, and there is little scope for IA or substantial... 

A most important technique which has been developed as an extension of the isotope dilution principle is that of radioimmunoassay (R1A). Analyses by this method employ substoichiometric amounts of specific binding immuno ... 

Subsequently, experimental procedures of dilution principle reactions were further improved and standardized, so that today it is possible to synthesize many desired compounds by suitable choice of components and dilution conditions. 

In the following chapters a progress report on recent syntheses using the dilution principle shall be given some examples of reactions which work without dilution conditions, but nevertheless use the basic ideas of the dilution principle, are presented, as well. 

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